Open Source Development With CVS

Copyright © 1999, 2000 Karl Fogel <kfogel@red-bean.com>

This document is free software; you can redistribute and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version.

This document is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

This manual describes how to use and administer CVS (Concurrent Versions System). It is part of a larger work entitled Open Source Development With CVS; please see the introduction for details.

This is version 1.21 of this manual.

## Short Contents

- Top
- Introduction
- An Overview of CVS
- Repository Administration
- Advanced CVS
- Tips And Troubleshooting
- CVS Reference
- Third-Party Tools
- Index
- GNU General Public License
- GNU Free Documentation License

## Table of Contents

- Top
- Introduction
- An Overview of CVS
  - Basic Concepts
  - A Day With CVS
    - Conventions Used In This Tour
    - Invoking CVS
    - Accessing A Repository
    - Starting A New Project
    - Checking Out A Working Copy
    - Version Versus Revision
    - Making A Change
    - Finding Out What You (And Others) Did - update And diff
    - CVS And Implied Arguments
    - Committing
    - Revision Numbers
    - Detecting And Resolving Conflicts
    - Finding Out Who Did What (Browsing Log Messages)
    - Examining And Reverting Changes
    - The Slow Method Of Reverting
    - The Fast Method Of Reverting
  - Other Useful CVS Commands
    - Adding Files
    - Adding Directories
    - CVS And Binary Files
    - Removing Files
    - Removing Directories
    - Renaming Files And Directories
    - Avoiding Option Fatigue
    - Getting Snapshots (Dates And Tagging)
    - Acceptable Date Formats
    - Marking A Moment In Time (Tags)
  - Branches
    - Branching Basics
    - Merging Changes From Branch To Trunk
    - Multiple Merges
    - Creating A Tag Or Branch Without A Working Copy
- Repository Administration
  - Getting And Installing CVS
    - Getting And Building CVS Under Unix
    - Getting And Installing CVS Under Windows
    - Getting And Installing CVS On A Macintosh
    - Limitations Of The Windows And Macintosh Versions
  - Anatomy Of A CVS Distribution
    - Informational Files
    - Subdirectories
    - The Cederqvist Manual
    - Other Sources Of Information
  - Starting A Repository
  - The Password-Authenticating Server
  - Anonymous Access
  - Repository Structure
  - RCS Format
  - What Happens When You Remove A File
  - The CVSROOT/ Administrative Directory
    - The config File
    - The modules File
    - The commitinfo And loginfo And rcsinfo Files
    - The verifymsg And rcsinfo Files
    - The taginfo File
    - The cvswrappers File
    - The editinfo File
    - The notify File
    - The checkoutlist File
  - Commit Emails
  - Finding Out More
- Advanced CVS
  - Watches (CVS As Telephone)
    - How Watches Work
    - Enabling Watches In The Repository
    - Using Watches In Development
    - Ending An Editing Session
    - Controlling What Actions Are Watched
    - Finding Out Who Is Watching What
    - Reminding People To Use Watches
    - What Watches Look Like In The Repository
  - Log Messages And Commit Emails
  - Changing A Log Message After Commit
  - Getting Rid Of A Working Copy
  - History - A Summary Of Repository Activity
  - Annotations - A Detailed View Of Project Activity
  - Annotations And Branches
  - Using Keyword Expansion
  - Going Out On A Limb (How To Work With Branches And Survive)
    - Some Principles For Working With Branches
    - Merging Repeatedly Into The Trunk
    - The Dovetail Approach - Merging In And Out Of The Trunk
    - The Flying Fish Approach - A Simpler Way To Do It
    - Branches And Keyword Expansion - Natural Enemies
  - Tracking Third-Party Sources (Vendor Branches)
  - Exporting For Public Distribution
  - The Humble Guru
- Tips And Troubleshooting
  - The Usual Suspects
    - The Working Copy Administrative Area
    - Repository Permissions
  - General Troubleshooting Tips
  - Some Real Life Problems (With Solutions)
    - CVS says it is waiting for a lock; what does that mean?
    - CVS claims a file is failing Up-To-Date check; what do I do?
    - The pserver access method is not working
    - The pserver access method is STILL not working
    - My commits seem to happen in pieces instead of atomically
    - CVS keeps changing file permissions; why does it do that?
    - CVS on Windows complains it cannot find my .cvspass file; why?
    - My working copy is on several different branches; help?
    - When I do export -d I sometimes miss recent commits
    - I get an error about val-tags; what should I do?
    - I am having problems with sticky tags; how do I get rid of them?
    - Checkouts/updates exit with error saying cannot expand modules
    - I cannot seem to turn off watches
    - My binary files are messed up
    - CVS is not doing line-end conversion correctly
    - I need to remove a subdirectory in my project; how do I do it?
    - Can I copy .cvspass files or portions of them?
    - I just committed some files with the wrong log message
    - I need to move files around without losing revision history
    - How can I get a list of all tags in a project?
    - How can I get a list of all projects in a repository?
    - Some commands fail remotely but not locally; how should I debug?
    - I do not see my problem covered in this chapter
    - I think I have discovered a bug in CVS; what do I do?
    - I have implemented a new feature for CVS; to whom do I send it?
    - How can I keep up with changes to CVS?
- CVS Reference
  - Commands And Options
    - Organization And Conventions
    - General Patterns In CVS Commands
    - Date Formats
    - Global Options
    - add
    - admin
    - annotate
    - checkout
    - commit
    - diff
    - edit
    - editors
    - export
    - gserver
    - history
    - import
    - init
    - kserver
    - log
    - login
    - logout
    - pserver
    - rdiff
    - release
    - remove
    - rtag
    - server
    - status
    - tag
    - unedit
    - update
    - watch
    - watchers
  - Keyword Substitution (RCS Keywords)
    - Controlling Keyword Expansion
    - List Of Keywords
  - Repository Administrative Files
    - Storage And Editing
    - Shared Syntax
    - Shared Variables
    - User Variables
    - checkoutlist
    - commitinfo
    - config
    - cvsignore
    - cvswrappers
    - editinfo
    - history file
    - loginfo
    - modules
    - notify
    - passwd
    - rcsinfo
    - taginfo
    - users
    - val-tags
    - verifymsg
  - Run Control Files
    - `.cvsrc`
    - `.cvsignore`
    - `.cvspass`
    - `.cvswrappers`
  - Working Copy Files
    - `CVS/Base/` (directory)
    - `CVS/Baserev`
    - `CVS/Baserev.tmp`
    - `CVS/Checkin.prog`
    - `CVS/Entries`
    - `CVS/Entries.Backup`
    - `CVS/Entries.Log`
    - `CVS/Entries.Static`
    - `CVS/Notify`
    - `CVS/Notify.tmp`
    - `CVS/Repository`
    - `CVS/Root`
    - `CVS/Tag`
    - `CVS/Template`
    - `CVS/Update.prog`
  - Environment Variables
    - $COMSPEC
    - $CVS_CLIENT_LOG
    - $CVS_CLIENT_PORT
    - $CVSEDITOR
    - $CVSIGNORE
    - $CVS_IGNORE_REMOTE_ROOT
    - $CVS_PASSFILE
    - $CVS_RCMD_PORT
    - $CVSREAD
    - $CVSROOT
    - $CVS_RSH
    - $CVS_SERVER
    - $CVS_SERVER_SLEEP
    - $CVSUMASK
    - $CVSWRAPPERS
    - $EDITOR
    - $HOME %HOMEDRIVE% %HOMEPATH%
    - $PATH
    - $TEMP $TMP $TMPDIR
    - $VISUAL
- Third-Party Tools
  - pcl-cvs - An Emacs Interface To CVS
    - Installing pcl-cvs
    - Using pcl-cvs
    - Error Handling In pcl-cvs
    - The Future Of pcl-cvs
  - cvsutils - General Utilities For Use With CVS
    - cvsu
    - cvsdo
    - cvschroot
    - cvsrmadm
    - cvspurge
    - cvsdiscard
    - cvsco
    - cvsdate
  - cvs2cl - Generate GNU-Style ChangeLogs
  - cvsq - Queue CVS Commands For Later Connection
  - cvslock - Lock Repositories For Atomicity
  - Other Packages
  - Writing Your Own Tools
- Index
- GNU General Public License
- GNU Free Documentation License

Node: Top, Next: Introduction, Up: (dir)

##

## Top

Node: Introduction, Next: An Overview of CVS, Previous: Top, Up: Top

## Introduction

This is a set of free, online chapters about using CVS (Concurrent Versions System) for collaboration and version control. It covers everything from CVS installation and basic concepts all the way to advanced usage and administration. It is intended for anyone who uses or plans to use CVS.

These chapters are excerpted from a larger work called Open Source Development With CVS (published by The Coriolis Group, ISBN 1-57610-490-7). The remainder of that book - chapters 1, 3, 5, and 7 - deals with the challenges and philosophical issues of running an Open Source project using CVS.

While the free chapters here constitute a complete CVS book by themselves, we certainly hope you'll like them enough to purchase a treeware copy of the entire book! You can order it directly from the publisher, at http://www.coriolis.com/bookstore/bookdetail.cfm?id=1576104907.

These chapters are released under the GNU General Public License. For more information about free software in general, visit http://www.gnu.org/, and particularly http://www.gnu.org/philosophy/free-sw.html.

To submit comments or errata regarding any of this material, please send email to bug-cvsbook@red-bean.com. For news and updates, visit http://cvsbook.red-bean.com/.

Node: An Overview of CVS, Next: Repository Administration, Previous: Introduction, Up: Top

## An Overview of CVS

> I can't imagine programming without it... that would be like parachuting without a parachute! -Brian Fitzpatrick on CVS

This chapter introduces the fundamentals of CVS, and then provides an in-depth guided tour of everyday CVS usage. Concepts are presented sequentially, so if you're new to CVS, the best way to read this is to start at the beginning and go straight through, without skipping anything.

Node: Basic Concepts, Next: A Day With CVS, Up: An Overview of CVS

### Basic Concepts

If you've never used CVS (or any version control system) before, it's easy to get tripped up by some of its underlying assumptions. What seems to cause the most initial confusion about CVS is that it is used for two apparently unrelated purposes: record keeping and collaboration. It turns out, however, that these two functions are closely connected.

Record keeping became necessary because people wanted to compare a program's current state with how it was at some point in the past. For example, in the normal course of implementing a new feature, a developer may bring the program into a thoroughly broken state, where it will probably remain until the feature is mostly finished. Unfortunately, this is just the time when someone usually calls to report a bug in the last publicly released version. To debug the problem (which may also exist in the current version of the sources), the program has to be brought back to a useable state.

Restoring the state poses no difficulty if the source code history is kept under CVS. The developer can simply say, in effect, "Give me the program as it was three weeks ago", or perhaps "Give me the program as it was at the time of our last public release". If you've never had this kind of convenient access to historical snapshots before, you may be surprised at how quickly you come to depend on it. Personally, I always use revision control on my coding projects now - it's saved me many times.

To understand what this has to do with facilitating collaboration, we'll need to take a closer look at the mechanism that CVS provides to help numerous people work on the same project. But before we do that, let's take a look at a mechanism that CVS doesn't provide (or at least, doesn't encourage): file locking. If you've used other version control systems, you may be familiar with the lock-modify-unlock development model, wherein a developer first obtains exclusive write access (a lock) to the file to be edited, makes the changes, and then releases the lock to allow other developers access to the file. If someone else already has a lock on the file, they have to "release" it before you can lock it and start making changes (or, in some implementations, you may "steal" their lock, but that is often an unpleasant surprise for them and not good practice!).

This system is workable if the developers know each other, know who's planning to do what at any given time, and can communicate with each other quickly if someone cannot work because of access contention. However, if the developer group becomes too large or too spread out, dealing with all the locking issues begins to chip away at coding time; it becomes a constant hassle that can discourage people from getting real work done.

CVS takes a more mellow approach. Rather than requiring that developers coordinate with each other to avoid conflicts, CVS enables developers to edit simultaneously, assumes the burden of integrating all the changes, and keeps track of any conflicts. This process uses the copy-modify-merge model, which works as follows:

1. Developer A requests a working copy (a directory tree containing the files that make up the project) from CVS. This is also known as "checking out" a working copy, like checking a book out of the library.
2. Developer A edits freely in her working copy. At the same time, other developers may be busy in their own working copies. Because these are all separate copies, there is no interference - it is as though all of the developers have their own copy of the same library book, and they're all at work scribbling comments in the margins or rewriting certain pages independently.
3. Developer A finishes her changes and commits them into CVS along with a "log message", which is a comment explaining the nature and purpose of the changes. This is like informing the library of what changes she made to the book and why. The library then incorporates these changes into a "master" copy, where they are recorded for all time.
4. Meanwhile, other developers can have CVS query the library to see if the master copy has changed recently. If it has, CVS automatically updates their working copies. (This part is magical and wonderful, and I hope you appreciate it. Imagine how different the world would be if real books worked this way!)

As far as CVS is concerned, all developers on a project are equal. Deciding when to update or when to commit is largely a matter of personal preference or project policy. One common strategy for coding projects is to always update before commencing work on a major change and to commit only when the changes are complete and tested so that the master copy is always in a "runnable" state.

Perhaps you're wondering what happens when developers A and B, each in their own working copy, make different changes to the same area of text and then both commit their changes? This is called a conflict, and CVS notices it as soon as developer B tries to commit changes. Instead of allowing developer B to proceed, CVS announces that it has discovered a conflict and places conflict markers (easily recognizable textual flags) at the conflicting location in his copy. That location also shows both sets of changes, arranged for easy comparison. Developer B must sort it all out and commit a new revision with the conflict resolved. Perhaps the two developers will need to talk to each other to settle the issue. CVS only alerts the developers that there is a conflict; it's up to human beings to actually resolve it.

What about the master copy? In official CVS terminology, it is called the project's repository. The repository is simply a file tree kept on a central server. Without going into too much detail about its structure (but see Repository Administration), let's look at what the repository must do to meet the requirements of the checkout-commit-update cycle. Consider the following scenario:

1. Two developers, A and B, check out working copies of a project at the same time. The project is at its starting point - no changes have been committed by anyone yet, so all the files are in their original, pristine state.
2. Developer A gets right to work and soon commits her first batch of changes.
3. Meanwhile, developer B watches television.
4. Developer A, hacking away like there's no tomorrow, commits her second batch of changes. Now, the repository's history contains the original files, followed by A's first batch of changes, followed by this set of changes.
5. Meanwhile, developer B plays video games.
6. Suddenly, developer C joins the project and checks out a working copy from the repository. Developer C's copy reflects A's first two sets of changes, because they were already in the repository when C checked out her copy.
7. Developer A, continuing to code as one possessed by spirits, completes and commits her third batch of changes.
8. Finally, blissfully unaware of the recent frenzy of activity, developer B decides it's time to start work. He doesn't bother to update his copy; he just commences editing files, some of which may be files that A has worked in. Shortly thereafter, developer B commits his first changes.

At this point, one of two things can happen. If none of the files edited by developer B have been edited by A, the commit succeeds. However, if CVS realizes that some of B's files are out of date with respect to the repository's latest copies, and those files have also been changed by B in his working copy, CVS informs B that he must do an update before committing those files.

When developer B runs the update, CVS merges all of A's changes into B's local copies of the files. Some of A's work may conflict with B's uncommitted changes, and some may not. Those parts that don't are simply applied to B's copies without further complication, but the conflicting changes must be resolved by B before being committed.

If developer C does an update now, she'll receive various new changes from the repository: those from A's third commit, and those from B's first successful commit (which might really come from B's second attempt to commit, assuming B's first attempt resulted in B being forced to resolve conflicts).

In order for CVS to serve up changes, in the correct sequence, to developers whose working copies may be out of sync by varying degrees, the repository needs to store all commits since the project's beginning. In practice, the CVS repository stores them all as successive diffs. Thus, even for a very old working copy, CVS is able to calculate the difference between the working copy's files and the current state of the repository, and is thereby able to bring the working copy up to date efficiently. This makes it easy for developers to view the project's history at any point and to revive even very old working copies.

Although, strictly speaking, the repository could achieve the same results by other means, in practice, storing diffs is a simple, intuitive means of implementing the necessary functionality. The process has the added benefit that, by using patch appropriately, CVS can reconstruct any previous state of the file tree and thus bring any working copy from one state to another. It can allow someone to check out the project as it looked at any particular time. It can also show the differences, in diff format, between two states of the tree without affecting someone's working copy.

Thus, the very features necessary to give convenient access to a project's history are also useful for providing a decentralized, uncoordinated developer team with the ability to collaborate on the project.

For now, you can ignore the details of setting up a repository, administering user access, and navigating CVS-specific file formats (those will be covered in Repository Administration). For the moment, we'll concentrate on how to make changes in a working copy.

But first, here is a quick review of terms:

- Revision A committed change in the history of a file or set of files. A revision is one "snapshot" in a constantly changing project.
- Repository The master copy where CVS stores a project's full revision history. Each project has exactly one repository.
- Working copy The copy in which you actually make changes to a project. There can be many working copies of a given project; generally each developer has his or her own copy.
- Check out To request a working copy from the repository. Your working copy reflects the state of the project as of the moment you checked it out; when you and other developers make changes, you must use commit and update to "publish" your changes and view others' changes.
- Commit To send changes from your working copy into the central repository. Also known as check-in.
- Log message A comment you attach to a revision when you commit it, describing the changes. Others can page through the log messages to get a summary of what's been going on in a project.
- Update To bring others' changes from the repository into your working copy and to show if your working copy has any uncommitted changes. Be careful not to confuse this with commit; they are complementary operations. Mnemonic: update brings your working copy up to date with the repository copy.
- Conflict The situation when two developers try to commit changes to the same region of the same file. CVS notices and points out conflicts, but the developers must resolve them.

Node: A Day With CVS, Next: Other Useful CVS Commands, Previous: Basic Concepts, Up: An Overview of CVS

### A Day With CVS

This section describes some basic CVS operations, then follows with a sample session covering typical CVS usage. As the guided tour progresses, we'll also start to look at how CVS works internally.

Although you don't need to understand every last detail of CVS's implementation to use it, a basic knowledge of how it works is invaluable in choosing the best way to achieve a given result. CVS is more like a bicycle than an automobile, in the sense that its mechanisms are entirely transparent to anyone who cares to look. As with a bicycle, you can just hop on and start riding immediately. However, if you take a few moments to study how the gears work, you'll be able to ride it much more efficiently. (In the case of CVS, I'm not sure whether transparency was a deliberate design decision or an accident, but it does seem to be a property shared by many free programs. Externally visible implementations have the advantage of encouraging the users to become contributing developers by exposing them to the system's inner workings right from the start.)

Each part of the tour may make use of knowledge introduced in previous parts. Therefore, if this is your first time, I recommend that you simply start at the beginning and take the tour sequentially, without skipping over anything. The menu below is merely meant as a convenience for repeat visitors - you shouldn't use it to jump directly to a section that interests you unless you're already familiar with the material in the previous sections.

Node: Conventions Used In This Tour, Next: Invoking CVS, Up: A Day With CVS

### Conventions Used In This Tour

The tour takes place in a Unix environment. CVS also runs on Windows and Macintosh operating systems, and Tim Endres of Ice Engineering has even written a Java client (see http://www.trustice.com/java/jcvs/), which can be run anywhere Java runs. However, I'm going to take a wild guess and assume that the majority of CVS users - present and potential - are most likely working in a Unix command-line environment. If you aren't one of these, the examples in the tour should be easy to translate to other interfaces. Once you understand the concepts, you can sit down at any CVS front end and work with it (trust me, I've done it many times).

The examples in the tour are oriented toward people who will be using CVS to keep track of programming projects. However, CVS operations are applicable to all text documents, not just source code.

The tour also assumes that you already have CVS installed (it's present by default on many of the popular free Unix systems, so you might already have it without knowing it) and that you have access to a repository. Even if you are not set up, you can still benefit from reading the tour. In Repository Administration, you'll learn how to install CVS and set up repositories.

Assuming CVS is installed, you should take a moment to find the online CVS manual. Known familiarly as the "Cederqvist" (after Per Cederqvist, its original author), it comes with the CVS source distribution and is usually the most up-to-date reference available. It's written in Texinfo format and should be available on Unix systems in the "Info" documentation hierarchy. You can read it either with the command line info program

         floss$ info cvs

or by pressing Ctrl+H and then typing "i" inside Emacs. If neither of these works for you, consult your local Unix guru (or see Repository Administration regarding installation issues). You'll definitely want to have the Cederqvist at your fingertips if you're going to be using CVS regularly.

Node: Invoking CVS, Next: Accessing A Repository, Previous: Conventions Used In This Tour, Up: A Day With CVS

### Invoking CVS

CVS is one program, but it can perform many different actions: updating, committing, branching, diffing, and so on. When you invoke CVS, you must specify which action you want to perform. Thus, the format of a CVS invocation is:

         floss$ cvs command

For example, you can use

         floss$ cvs update
         floss$ cvs diff
         floss$ cvs commit

and so on. (Don't bother to try running any of those particular commands yet, though; they won't do anything until you're in a working copy, which we'll get to shortly.)

Both CVS and the command can take options. Options that affect the behavior of CVS, independently of the command being run, are called global options; command-specific options are just called command options. Global options always go to the left of the command; command options, to its right. So in

         floss$ cvs -Q update -p

-Q is a global option, and -p is a command option. (If you're curious, -Q means "quietly"-that is, suppress all diagnostic output, and print error messages only if the command absolutely cannot be completed for some reason; -p means to send the results of update to standard output instead of to files.)

Node: Accessing A Repository, Next: Starting A New Project, Previous: Invoking CVS, Up: A Day With CVS

### Accessing A Repository

Before you can do anything, you must tell CVS the location of the repository you'll be accessing. This isn't a concern if you already have a working copy checked out - any working copy knows what repository it came from, so CVS can automatically deduce the repository for a given working copy. However, let's assume you don't have a working copy yet, so you need to tell CVS explicitly where to go. This is done with the -d global option (the -d stands for "directory", an abbreviation for which there is a historical justification, although -r for "repository" might have been better), followed by the path to the repository. For example, assuming the repository is on the local machine in /usr/local/cvs (a fairly standard location):

         floss$ cvs -d /usr/local/cvs command

In many cases, however, the repository is on another machine and must therefore be reached over the network. CVS provides a choice of network access methods; which one you'll use depends mostly on the security needs of the repository machine (hereinafter referred to as "the server"). Setting up the server to allow various remote access methods is covered in Repository Administration; here we'll deal only with the client side.

Fortunately, all the remote access methods share a common invocation syntax. In general, to specify a remote repository as opposed to a local one, you just use a longer repository path. You first name the access method, delimited on each side by colons, followed by the username and the server name (joined with an @ sign), another separator colon, and finally the path to the repository directory on the server.

Let's look at the pserver access method, which stands for "password-authenticated server":

         floss$ cvs -d :pserver:jrandom@cvs.foobar.com:/usr/local/cvs login
         (Logging in to jrandom@cvs.foobar.com)
         CVS password: (enter your CVS password here)
         floss$

The long repository path following -d told CVS to use the pserver access method, with the username jrandom, on the server cvs.foobar.com, which has a CVS repository in /usr/local/cvs. There's no requirement that the hostname be "cvs.something.com" by the way; that's a common convention, but it could just as easily have been:

         floss$ cvs -d :pserver:jrandom@fish.foobar.org:/usr/local/cvs command

The command actually run was login, which verifies that you are authorized to work with this repository. It prompts for a password, then contacts the server to verify the password. Following Unix custom, cvs login returns silently if the login succeeds; it shows an error message if it fails (for instance, because the password is incorrect).

You only have to log in once from your local machine to a given CVS server. After a successful login, CVS stores the password in your home directory, in a file called .cvspass. It consults that file every time a repository is contacted via the pserver method, so you only have to run login the first time you access a given CVS server from a particular client machine. Of course, you can rerun cvs login anytime if the password changes.

Note: pserver is currently the only access method requiring an initial login like this; with the others, you can start running regular CVS commands immediately.

Once you've stored the authentication information in your .cvspass file, you can run other CVS commands using the same command-line syntax:

         floss$ cvs -d :pserver:jrandom@cvs.foobar.com:/usr/local/cvs command

Getting pserver to work in Windows may require an extra step. Windows doesn't have the Unix concept of a home directory, so CVS doesn't know where to put the .cvspass file. You'll have to specify a location. It's normal to designate the root of the C: drive as the home directory:

         C:\WINDOWS> set HOME=C:
         C:\WINDOWS> cvs -d :pserver:jrandom@cvs.foobar.com:/usr/local/cvs login
         (Logging in to jrandom@cvs.foobar.com)
         CVS password: (enter password here)
         C:\WINDOWS>

Any folder in the file system will suffice. You may want to avoid network drives, though, because the contents of your .cvspass file would then be visible to anyone with access to the drive.

In addition to pserver, CVS supports the ext method (which uses an external connection program, such as rsh or ssh), kserver (for the Kerberos security system version 4), and gserver (which uses the GSSAPI, or Generic Security Services API, and also handles Kerberos versions 5 and higher). These methods are similar to pserver, but each has its own idiosyncrasies.

Of these, the `ext` method is probably the most commonly used. If you can log into the server with rsh or ssh, you can use the `ext` method. You can test it like this:

         floss$ rsh -l jrandom cvs.foobar.com
         Password: enter your login password here

Okay, let's assume you successfully logged in and logged out of the server with rsh, so now you're back on the original client machine:

         floss$ CVS_RSH=rsh; export CVS_RSH
         floss$ cvs -d :ext:jrandom@cvs.foobar.com:/usr/local/cvs command

The first line sets (in Unix Bourne shell syntax) the CVS_RSH environment variable to rsh, which tells CVS to use the rsh program to connect. The second line can be any CVS command; you will be prompted for your password so CVS can log into the server.

If you're in C shell rather than in Bourne shell, try this:

         floss% setenv CVS_RSH rsh

and for Windows, try this:

         C:\WINDOWS> set CVS_RSH=rsh

The rest of the tour will use the Bourne syntax; translate for your environment as necessary.

To use ssh (the Secure Shell) instead of rsh, just set the CVS_RSH variable appropriately:

         floss$ CVS_RSH=ssh; export CVS_RSH

Don't get thrown by the fact that the variable's name is CVS_RSH but you're setting its value to ssh. There are historical reasons for this (the catch-all Unix excuse, I know). CVS_RSH can point to the name of any program capable of logging you into the remote server, running commands, and receiving their output. After rsh, ssh is probably the most common such program, although there are probably others. Note that this program must not modify its data stream in any way. This disqualifies the Windows NT rsh, because it converts (or attempts to convert) between the DOS and Unix line-ending conventions. You'd have to get some other rsh for Windows or use a different access method.

The gserver and kserver methods are not used as often as the others and are not covered here. They're quite similar to what we've covered so far; see the Cederqvist for details.

If you only use one repository and don't want to type -d repos each time, just set the CVSROOT environment variable (which perhaps should have been named CVSREPOS, but it's too late to change that now):

         floss$ CVSROOT=/usr/local/cvs
         floss$ export CVSROOT
         floss$ echo $CVSROOT
         /usr/local/cvs
         floss$

or maybe

         floss$ CVSROOT=:pserver:jrandom@cvs.foobar.com:/usr/local/cvs
         floss$ export CVSROOT
         floss$ echo $CVSROOT
         :pserver:jrandom@cvs.foobar.com:/usr/local/cvs
         floss$

The rest of this tour assumes that you've set CVSROOT to point to your repository, so the examples will not show the -d option. If you need to access many different repositories, you should not set CVSROOT and should just use -d repos when you need to specify the repository.

Node: Starting A New Project, Next: Checking Out A Working Copy, Previous: Accessing A Repository, Up: A Day With CVS

### Starting A New Project

If you're learning CVS in order to work on a project that's already under CVS control (that is, it is kept in a repository somewhere), you'll probably want to skip down to the next section, "Checking Out A Working Copy." On the other hand, if you want to take existing source code and put it into CVS, this is the section for you. Note that it still assumes you have access to an existing repository; see Repository Administration if you need to set up a repository first.

Putting a new project into a CVS repository is known as importing. The CVS command, as you may have guessed, is

         floss$ cvs import

except that it needs some more options (and needs to be in the right location) to succeed. First, go into the top-level directory of your project tree:

         floss$ cd myproj
         floss$ ls
         README.txt  a-subdir/   b-subdir/   hello.c
         floss$

This project has two files - README.txt and hello.c - in the top level, plus two subdirectories - a-subdir and b-subdir - plus some more files (not shown in the example) inside those subdirectories. When you import a project, CVS imports everything in the tree, starting from the current directory and working its way down. Therefore, you should make sure that the only files in the tree are ones you want to be permanent parts of the project. Any old backup files, scratch files, and so on should all be cleaned out.

The general syntax of an import command is

         floss$ cvs import -m "log msg" projname vendortag releasetag

The -m flag (for message) is for specifying a short message describing the import. This will be the first log message for the entire project; every commit thereafter will also have its own log message. These messages are mandatory; if you don't give the -m flag, CVS automatically starts up an editor (by consulting the EDITOR environment variable) for you to type a log message in. After you save the log message and exit the editor, the import then continues.

The next argument is the project's name (we'll use "myproj"). This is the name under which you'll check out the project from the repository. (What actually happens is that a directory of that name gets created in the repository, but more on that in Repository Administration.) The name you choose now does not need to be the same as the name of the current directory, although in most cases it usually is.

The vendortag and releasetag arguments are a bit of bookkeeping for CVS. Don't worry about them now; it hardly matters what you use. In Advanced CVS you'll learn about the rare circumstances where they're significant. For now, we'll use a username and "start" for those arguments.

We're ready to run import:

         floss$ cvs import -m "initial import into CVS" myproj jrandom start
         N myproj/hello.c
         N myproj/README.txt
         cvs import: Importing /usr/local/cvs/myproj/a-subdir
         N myproj/a-subdir/whatever.c
         cvs import: Importing /usr/local/cvs/myproj/a-subdir/subsubdir
         N myproj/a-subdir/subsubdir/fish.c
         cvs import: Importing /usr/local/cvs/myproj/b-subdir
         N myproj/b-subdir/random.c

         No conflicts created by this import
         floss$

Congratulations! If you ran that command (or something similar), you've finally done something that affects the repository.

Reading over the output of the import command, you'll notice that CVS precedes each filename with a single letter - in this case, "N" for "new file". The use of a single letter on the left to indicate the status of a file is a general pattern in CVS command output. We'll see it later in checkout and update as well.

You might think that, having just imported the project, you can start working in the tree immediately. This is not the case, however. The current directory tree is still not a CVS working copy. It was the source for the import command, true, but it wasn't magically changed into a CVS working copy merely by virtue of having been imported. To get a working copy, you need to check one out from the repository.

First, though, you might want to archive the current project tree. The reason is that once the sources are in CVS, you don't want to confuse yourself by accidentally editing copies that aren't in version control (because those changes won't become part of the project's history). You want to do all of your editing in a working copy from now on. However, you also don't want to remove the imported tree entirely, because you haven't yet verified that the repository actually has the files. Of course, you can be 99.999 percent certain that it does because the import command returned with no error, but why take chances? Paranoia pays, as every programmer knows. Therefore, do something like this:

         floss$ ls
         README.txt  a-subdir/   b-subdir/   hello.c
         floss$ cd ..
         floss$ ls
         myproj/
         floss$ mv myproj was_myproj
         floss$ ls
         was_myproj/
         floss$

There. You still have the original files, but they're clearly named as an obsolete version, so they won't be in the way when you get a real working copy. Now you're ready to check out.

Node: Checking Out A Working Copy, Next: Version Versus Revision, Previous: Starting A New Project, Up: A Day With CVS

### Checking Out A Working Copy

The command to check out a project is exactly what you think it is:

         floss$ cvs checkout myproj
         cvs checkout: Updating myproj
         U myproj/README.txt
         U myproj/hello.c
         cvs checkout: Updating myproj/a-subdir
         U myproj/a-subdir/whatever.c
         cvs checkout: Updating myproj/a-subdir/subsubdir
         U myproj/a-subdir/subsubdir/fish.c
         cvs checkout: Updating myproj/b-subdir
         U myproj/b-subdir/random.c

         floss$ ls
         myproj/      was_myproj/
         floss$ cd myproj
         floss$ ls
         CVS/        README.txt  a-subdir/   b-subdir/   hello.c
         floss$

Behold - your first working copy! Its contents are exactly the same as what you imported, with the addition of a subdirectory named "CVS". That's where CVS stores version control information. Actually, each directory in the project has a CVS subdirectory:

         floss$ ls a-subdir
         CVS/        subsubdir/  whatever.c
         floss$ ls a-subdir/subsubdir/
         CVS/    fish.c
         floss$ ls b-subdir
         CVS/      random.c

The fact that CVS keeps its revision information in subdirectories named CVS means that your project can never contain subdirectories of its own named CVS. In practice, I've never heard of this being a problem.

Before editing any files, let's take a peek inside the black box:

         floss$ cd CVS
         floss$ ls
         Entries     Repository  Root
         floss$ cat Root
         /usr/local/cvs
         floss$ cat Repository
         myproj
         floss$

Nothing too mysterious there. The Root file points to repository, and the Repository file points to a project inside the repository. If that's a little confusing, let me explain.

There is a longstanding confusion about terminology in CVS. The word "repository" is used to refer to two different things. Sometimes, it means the root directory of a repository (for example, /usr/local/cvs), which can contain many projects; this is what the Root file refers to. But other times, it means one particular project-specific subdirectory within a repository root (for example, /usr/local/cvs/myproj, /usr/local/cvs/yourproj, or /usr/local/cvs/fish). The Repository file inside a CVS subdirectory takes the latter meaning.

In this book, "repository" generally means Root (that is, the top-level repository), although it may occasionally be used to mean a project-specific subdirectory. If the intended sense can't be figured out from the context, there will be clarifying text. Note that the Repository file may sometimes contain an absolute path to the project name instead of a relative path. This can make it slightly redundant with the Root file:

         floss$ cd CVS
         floss$ cat Root
         :pserver:jrandom@cvs.foobar.com:/usr/local/cvs
         floss$ cat Repository
         /usr/local/cvs/myproj
         floss$

The Entries file stores information about the individual files in the project. Each line deals with one file, and there are only lines for files or subdirectories in the immediate parent directory. Here's the top-level CVS/Entries file in myproj:

         floss$ cat Entries
         /README.txt/1.1.1.1/Sun Apr 18 18:18:22 1999//
         /hello.c/1.1.1.1/Sun Apr 18 18:18:22 1999//
         D/a-subdir////
         D/b-subdir////

The format of each line is

         /filename/revision number/last modification date//

and the directory lines are prefixed with "D". (CVS doesn't really keep a change history for directories, so the fields for revision number and datestamp are empty.)

The datestamps record the date and time of the last update (in Universal Time, not local time) of the files in the working copy. That way, CVS can easily tell whether a file has been modified since the last checkout, update, or commit. If the file system timestamp differs from the timestamp in the CVS/Entries file, CVS knows (without even having to consult the repository) that the file was probably modified.

If you take a look at the CVS/* files in one of the subdirectories

         floss$ cd a-subdir/CVS
         floss$ cat Root
         /usr/local/cvs
         floss$ cat Repository
         myproj/a-subdir
         floss$ cat Entries
         /whatever.c/1.1.1.1/Sun Apr 18 18:18:22 1999//
         D/subsubdir////
         floss$

you can see that the root repository has not changed, but the Repository file spells out the location of this subdirectory of the project, and the Entries file contains different lines.

Immediately after import, the revision number of every file in the project is shown as 1.1.1.1. This initial revision number is a bit of a special case, so we won't examine it in detail just yet; we'll take a closer look at revision numbers after we've committed some changes.

Node: Version Versus Revision, Next: Making A Change, Previous: Checking Out A Working Copy, Up: A Day With CVS

### Version Versus Revision

The internal revision number that CVS keeps for each file is unrelated to the version number of the software product of which the files are part. For example, you may have a project composed of three files, whose internal revision numbers on May 3, 1999, were 1.2, 1.7, and 2.48. On that day, you package up a new release of the software and release it as SlickoSoft Version 3. This is purely a marketing decision and doesn't affect the CVS revisions at all. The CVS revision numbers are invisible to your customers (unless you give them repository access); the only publicly visible number is the "3" in Version 3. You could have called it Version 1729 as far as CVS is concerned - the version number (or "release" number) has nothing to do with CVS's internal change tracking.

To avoid confusion, I'll use the word "revision" to refer exclusively to the internal revision numbers of files under CVS control. I may still call CVS a "version control system", however, because "revision control system" just sounds too awkward.

Node: Making A Change, Next: Finding Out What You (And Others) Did -- update And diff, Previous: Version Versus Revision, Up: A Day With CVS

### Making A Change

The project as it stands doesn't do much. Here are the contents of hello.c:

         floss$ cat hello.c
         #include <stdio.h>

         void
         main ()
         {
            printf ("Hello, world!\n");
         }

Let's make the first change to the project since importing it; we'll add the line

         printf ("Goodbye, world!\n");

right after the Hello, world!. Invoke your favorite editor and make the change:

         floss$ emacs hello.c
           ...

This was a fairly simple change, one where you're not likely to forget what you did. But in a larger, more complex project, it's quite possible you may edit a file, be interrupted by something else, and return several days later and be unable to remember exactly what you did, or even to remember if you changed anything at all. Which brings us to our first "CVS Saves Your Life" situation: comparing your working copy against the repository.

Node: Finding Out What You (And Others) Did -- update And diff, Next: CVS And Implied Arguments, Previous: Making A Change, Up: A Day With CVS

### Finding Out What You (And Others) Did - update And diff

Previously, I've talked about updating as a way of bringing changes down from the repository into your working copy - that is, as a way of getting other people's changes. However, update is really a bit more complex; it compares the overall state of the working copy with the state of the project in the repository. Even if nothing in the repository has changed since checkout, something in the working copy may have, and update will show that, too:

         floss$ cvs update
         cvs update: Updating .
         M hello.c
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir

The M next to hello.c means the file has been modified since it was last checked out, and the modifications have not yet been committed to the repository.

Sometimes, merely knowing which files you've edited is all you need. However, if you want a more detailed look at the changes, you can get a full report in diff format. The diff command compares the possibly modified files in the working copy to their counterparts in the repository and displays any differences:

         floss$ cvs diff
         cvs diff: Diffing .
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.1.1.1
         diff -r1.1.1.1 hello.c
         6a7
         >   printf ("Goodbye, world!\n");
         cvs diff: Diffing a-subdir
         cvs diff: Diffing a-subdir/subsubdir
         cvs diff: Diffing b-subdir

That's helpful, if a bit obscure, but there's still a lot of cruft in the output. For starters, you can ignore most of the first few lines. They just name the repository file and give the number of the last checked-in revision. These are useful pieces of information under other circumstances (we'll look more closely at them later), but you don't need them when you're just trying to get a sense of what changes have been made in the working copy.

A more serious impediment to reading the diff is that CVS is announcing its entry as it goes into each directory during the update. This can be useful during long updates on large projects, as it gives you a sense of how much longer the command will take, but right now it's just getting in the way of reading the diff. Let's tell CVS to be quiet about where it's working, with the -Q global option:

         floss$ cvs -Q diff
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.1.1.1
         diff -r1.1.1.1 hello.c
         6a7
         >   printf ("Goodbye, world!\n");

Better - at least some of the cruft is gone. However, the diff is still hard to read. It's telling you that at line 6, a new line was added (that is, what became line 7), whose contents were:

         printf ("Goodbye, world!\n");

The preceding ">" in the diff tells you that this line is present in the newer version of the file but not in the older one.

The format could be made even more readable, however. Most people find "context" diff format easier to read because it displays a few lines of context on either side of a change. Context diffs are generated by passing the -c flag to diff:

         floss$ cvs -Q diff -c
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.1.1.1
         diff -c -r1.1.1.1 hello.c
         *** hello.c     1999/04/18 18:18:22     1.1.1.1
         --- hello.c     1999/04/19 02:17:07
         ***************
         *** 4,7 ****
         ---4,8 --
           main ()
           {
             printf ("Hello, world!\n");
         +   printf ("Goodbye, world!\n");
           }

Now that's clarity! Even if you're not used to reading context diffs, a glance at the preceding output will probably make it obvious what happened: a new line was added (the + in the first column signifies an added line) between the line that prints Hello, world! and the final curly brace.

We don't need to be able to read context diffs perfectly (that's patch's job), but it's worth taking the time to acquire at least a passing familiarity with the format. The first two lines (after the introductory cruft) are

         *** hello.c     1999/04/18 18:18:22     1.1.1.1
         --- hello.c     1999/04/19 02:17:07

and they tell you what is being diffed against what. In this case, revision 1.1.1.1 of hello.c is being compared against a modified version of the same file (thus, there's no revision number for the second line, because only the working copy's changes haven't been committed to the repository yet). The lines of asterisks and dashes identify sections farther down in the diff. Later on, a line of asterisks, with a line number range embedded, precedes a section from the original file. Then a line of dashes, with a new and potentially different line number range embedded, precedes a section from the modified file. These sections are organized into contrasting pairs (known as "hunks"), one side from the old file and the other side from the new.

Our diff has one hunk:

         ***************
         *** 4,7 ****
         --- 4,8 --
           main ()
           {
             printf ("Hello, world!\n");
         +   printf ("Goodbye, world!\n");
           }

The first section of the hunk is empty, meaning that no material was removed from the original file. The second section shows that, in the corresponding place in the new file, one line has been added; it's marked with a "+". (When diff quotes excerpts from files, it reserves the first two columns on the left for special codes, such as "+" so the entire excerpt appears to be indented by two spaces. This extra indentation is stripped off when the diff is applied, of course.)

The line number ranges show the hunk's coverage, including context lines. In the original file, the hunk was in lines 4 through 7; in the new file, it's lines 4 through 8 (because a line has been added). Note that the diff didn't need to show any material from the original file because nothing was removed; it just showed the range and moved on to the second half of the hunk.

Here's another context diff, from an actual project of mine:

         floss$ cvs -Q diff -c
         Index: cvs2cl.pl
         ===================================================================
         RCS file: /usr/local/cvs/kfogel/code/cvs2cl/cvs2cl.pl,v
         retrieving revision 1.76
         diff -c -r1.76 cvs2cl.pl
         *** cvs2cl.pl   1999/04/13 22:29:44     1.76
         --- cvs2cl.pl   1999/04/19 05:41:37
         ***************
         *** 212,218 ****
                   # can contain uppercase and lowercase letters, digits, '-',
                   # and '_'. However, it's not our place to enforce that, so
                   # we'll allow anything CVS hands us to be a tag:
         !         /^\s([^:]+): ([0-9.]+)$/;
                   push (@{$symbolic_names{$2}}, $1);
                 }
               }
         -- 212,218 --
                   # can contain uppercase and lowercase letters, digits, '-',
                   # and '_'. However, it's not our place to enforce that, so
                   # we'll allow anything CVS hands us to be a tag:
         !         /^\s([^:]+): ([\d.]+)$/;
                   push (@{$symbolic_names{$2}}, $1);
                 }
               }

The exclamation point shows that the marked line differs between the old and new files. Since there are no "+" or "-" signs, we know that the total number of lines in the file has remained the same.

Here's one more context diff from the same project, slightly more complex this time:

         floss$ cvs -Q diff -c
         Index: cvs2cl.pl
         ===================================================================
         RCS file: /usr/local/cvs/kfogel/code/cvs2cl/cvs2cl.pl,v
         retrieving revision 1.76
         diff -c -r1.76 cvs2cl.pl
         *** cvs2cl.pl   1999/04/13 22:29:44     1.76
         --- cvs2cl.pl   1999/04/19 05:58:51
         ***************
         *** 207,217 ****
         }
                 else    # we're looking at a tag name, so parse & store it
                 {
         -         # According to the Cederqvist manual, in node "Tags", "Tag
         -         # names must start with an uppercase or lowercase letter and
         -         # can contain uppercase and lowercase letters, digits, '-',
         -         # and '_'. However, it's not our place to enforce that, so
         -         # we'll allow anything CVS hands us to be a tag:
                   /^\s([^:]+): ([0-9.]+)$/;
                   push (@{$symbolic_names{$2}}, $1);
                 }
         - 207,212 --
         ***************
         *** 223,228 ****
         --- 218,225 --
               if (/^revision (\d\.[0-9.]+)$/) {
                 $revision = "$1";
               }
         +
         +     # This line was added, I admit, solely for the sake of a diff example.

               # If have file name but not time and author, and see date or
               # author, then grab them:

This diff has two hunks. In the first, five lines were removed (these lines are only shown in the first section of the hunk, and the second section's line count shows that it has five fewer lines). An unbroken line of asterisks forms the boundary between hunks, and in the second hunk we see that two lines have been added: a blank line and a pointless comment. Note how the line numbers compensate for the effect of the previous hunk. In the original file, the second hunk's range of the area was lines 223 through 228; in the new file, because of the deletion that took place in the first hunk, the range is in lines 218 through 225.

Congratulations, you are probably now as expert as you'll ever need to be at reading diffs.

Node: CVS And Implied Arguments, Next: Committing, Previous: Finding Out What You (And Others) Did -- update And diff, Up: A Day With CVS

### CVS And Implied Arguments

In each of the CVS commands so far, you may have noticed that no files were specified on the command line. We ran

         floss$ cvs diff

instead of

         floss$ cvs diff hello.c

and

         floss$ cvs update

instead of

         floss$ cvs update hello.c

The principle at work here is that if you don't name any files, CVS acts on all files for which the command could possibly be appropriate. This even includes files in subdirectories beneath the current directory; CVS automatically descends from the current directory through every subdirectory in the tree. For example, if you modified b-subdir/random.c and a-subdir/subsubdir/fish.c, running update may result in this:

         floss$ cvs update
         cvs update: Updating .
         M hello.c
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         M a-subdir/subsubdir/fish.c
         cvs update: Updating b-subdir
         M b-subdir/random.c
         floss$

or better yet:

         floss$ cvs -q update
         M hello.c
         M a-subdir/subsubdir/fish.c
         M b-subdir/random.c
         floss$

Note: The -q flag is a less emphatic version of -Q. Had we used -Q, the command would have printed out nothing at all, because the modification notices are considered nonessential informational messages. Using the lowercase -q is less strict; it suppresses the messages we probably don't want, while allowing certain, more useful messages to pass through.

You can also name specific files for the update:

         floss$ cvs update hello.c b-subdir/random.c
         M hello.c
         M b-subdir/random.c
         floss$

and CVS will only examine those files, ignoring all others.

In truth, it's more common to run update without restricting it to certain files. In most situations, you'll want to update the entire directory tree at once. Remember, the updates we're doing here only show that some files have been locally modified, because nothing has changed yet in the repository. When other people are working on the project with you, there's always the chance that running update will pull some new changes down from the repository and incorporate them into your local files. In that case, you may find it slightly more useful to name which files you want updated.

The same principle can be applied to other CVS commands. For example, with diff, you can choose to view the changes one file at a time

         floss$ cvs diff -c b-subdir/random.c
         Index: b-subdir/random.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.1.1.1
         diff -c -r1.1.1.1 random.c
         *** b-subdir/random.c   1999/04/18 18:18:22     1.1.1.1
         --- b-subdir/random.c   1999/04/19 06:09:48
         ***************
         *** 1 ****
         ! /* A completely empty C file. */
         --- 1,8 --
         ! /* Print out a random number. */
         !
         ! #include <stdio.h>
         !
         ! void main ()
         ! {
         !   printf ("a random number\n");
         ! }

or see all the changes at once (hang on to your seat, this is going to be a big diff):

         floss$ cvs -Q diff -c
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.1.1.1
         diff -c -r1.1.1.1 hello.c
         *** hello.c     1999/04/18 18:18:22     1.1.1.1
         --- hello.c     1999/04/19 02:17:07
         ***************
         *** 4,7 ****
         --- 4,8 --
           main ()
           {
             printf ("Hello, world!\n");
         +   printf ("Goodbye, world!\n");
           }
         Index: a-subdir/subsubdir/fish.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/a-subdir/subsubdir/fish.c,v
         retrieving revision 1.1.1.1
         diff -c -r1.1.1.1 fish.c
         *** a-subdir/subsubdir/fish.c   1999/04/18 18:18:22     1.1.1.1
         --- a-subdir/subsubdir/fish.c   1999/04/19 06:08:50
         ***************
         *** 1 ****
         ! /* A completely empty C file. */
         --- 1,8 --
         ! #include <stdio.h>
         !
         ! void main ()
         ! {
         !   while (1) {
         !     printf ("fish\n");
         !   }
         ! }
         Index: b-subdir/random.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.1.1.1
         diff -c -r1.1.1.1 random.c
         *** b-subdir/random.c   1999/04/18 18:18:22     1.1.1.1
         --- b-subdir/random.c   1999/04/19 06:09:48
         ***************
         *** 1 ****
         ! /* A completely empty C file. */
         --- 1,8 --
         ! /* Print out a random number. */
         !
         ! #include <stdio.h>
         !
         ! void main ()
         ! {
         !   printf ("a random number\n");
         ! }

Anyway, as you can see from these diffs, this project is clearly ready for prime time. Let's commit the changes to the repository.

Node: Committing, Next: Revision Numbers, Previous: CVS And Implied Arguments, Up: A Day With CVS

### Committing

The commit command sends modifications to the repository. If you don't name any files, a commit will send all changes to the repository; otherwise, you can pass the names of one or more files to be committed (other files would be ignored, in that case).

Here, we commit one file by name and two by inference:

         floss$ cvs commit -m "print goodbye too" hello.c
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <--  hello.c
         new revision: 1.2; previous revision: 1.1
         done
         floss$ cvs commit -m "filled out C code"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in a-subdir/subsubdir/fish.c;
         /usr/local/cvs/myproj/a-subdir/subsubdir/fish.c,v  <--  fish.c
         new revision: 1.2; previous revision: 1.1
         done
         Checking in b-subdir/random.c;
         /usr/local/cvs/myproj/b-subdir/random.c,v  <--  random.c
         new revision: 1.2; previous revision: 1.1
         done
         floss$

Take a moment to read over the output carefully. Most of what it says is pretty self-explanatory. One thing you may notice is that revision numbers have been incremented (as expected), but the original revisions are listed as 1.1 instead of 1.1.1.1 as we saw in the Entries file earlier.

There is an explanation for this discrepancy, but it's not very important. It concerns a special meaning that CVS attaches to revision 1.1.1.1. For most purposes, we can just say that files receive a revision number of 1.1 when imported, but the number is displayed - for reasons known only to CVS - as 1.1.1.1 in the Entries file, until the first commit.

Node: Revision Numbers, Next: Detecting And Resolving Conflicts, Previous: Committing, Up: A Day With CVS

### Revision Numbers

Each file in a project has its own revision number. When a file is committed, the last portion of the revision number is incremented by one. Thus, at any given time, the various files comprising a project may have very different revision numbers. This just means that some files have been changed (committed) more often than others.

(You may be wondering, what's the point of the part to the left of the decimal point, if only the part on the right ever changes? Actually, although CVS never automatically increments the number on the left, that number can be incremented on request by a user. This is a rarely used feature, and we won't cover it in this tour.)

In the example project that we've been using, we just committed changes to three files. Each of those files is now revision 1.2, but the remaining files in the project are still revision 1.1. When you check out a project, you get each file at its highest revision so far. Here is what qsmith would see if he checked out myproj right now and looked at the revision numbers for the top-level directory:

         paste$ cvs -q -d :pserver:qsmith@cvs.foobar.com:/usr/local/cvs co myproj
         U myproj/README.txt
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         paste$ cd myproj/CVS
         paste$ cat Entries
         /README.txt/1.1.1.1/Sun Apr 18 18:18:22 1999//
         /hello.c/1.2/Mon Apr 19 06:35:15 1999//
         D/a-subdir////
         D/b-subdir////
         paste$

The file hello.c (among others) is now at revision 1.2, while README.txt is still at the initial revision (revision 1.1.1.1, also known as 1.1).

If he adds the line

         printf ("between hello and goodbye\n");

to hello.c and commit it, the file's revision number will be incremented once more:

         paste$ cvs ci -m "added new middle line"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <--  hello.c
         new revision: 1.3; previous revision: 1.2
         done
         paste$

Now hello.c is revision 1.3, fish.c and random.c still are revision 1.2, and every other file is revision 1.1.

Note: that the command was given as cvs ci instead of cvs commit. Most CVS commands have short forms, to make typing easier. For checkout, update, and commit, the abbreviated versions are co, up, and ci, respectively. You can get a list of all of the short forms by running the command `cvs --help-synonyms`.

You can usually ignore a file's revision number. In most situations, the numbers are just internal bookkeeping that CVS handles automatically. However, being able to find and compare revision numbers is extremely handy when you have to retrieve (or diff against) an earlier copy of a file.

Examining the Entries file isn't the only way to discover a revision number. You can also use the status command

         paste$ cvs status hello.c
         ===================================================================
         File: hello.c           Status: Up-to-date

            Working revision:    1.3     Tue Apr 20 02:34:42 1999
            Repository revision: 1.3     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

which, if invoked without any files being named, shows the status of every file in the project:

         paste$ cvs status
         cvs status: Examining.
         ===================================================================
         File: README.txt        Status: Up-to-date

            Working revision:    1.1.1.1 Sun Apr 18 18:18:22 1999
            Repository revision: 1.1.1.1 /usr/local/cvs/myproj/README.txt,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         ===================================================================
         File: hello.c           Status: Up-to-date

            Working revision:    1.3     Tue Apr 20 02:34:42 1999
            Repository revision: 1.3     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         cvs status: Examining a-subdir
         ===================================================================
         File: whatever.c        Status: Up-to-date

            Working revision:    1.1.1.1 Sun Apr 18 18:18:22 1999
            Repository revision: 1.1.1.1 /usr/local/cvs/myproj/a-subdir/whatever.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         cvs status: Examining a-subdir/subsubdir
         ===================================================================
         File: fish.c            Status: Up-to-date

            Working revision:    1.2     Mon Apr 19 06:35:27 1999
            Repository revision: 1.2     /usr/local/cvs/myproj/
                                         a-subdir/subsubdir/fish.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         cvs status: Examining b-subdir
         ===================================================================
         File: random.c          Status: Up-to-date

            Working revision:    1.2     Mon Apr 19 06:35:27 1999
            Repository revision: 1.2     /usr/local/cvs/myproj/b-subdir/random.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         paste$

Just ignore the parts of that output that you don't understand. In fact, that's generally good advice with CVS. Often, the one little bit of information you're looking for will be accompanied by reams of information that you don't care about at all, and maybe don't even understand. This situation is normal. Just pick out what you need, and don't worry about the rest.

In the previous example, the parts we care about are the first three lines (not counting the blank line) of each file's status output. The first line is the most important; it tells you the file's name, and its status in the working copy. All of the files are currently in sync with the repository, so they all say `Up-to-date`. However, if random.c has been modified but not committed, it might read like this:

         ===================================================================
         File: random.c          Status: Locally Modified

            Working revision:    1.2     Mon Apr 19 06:35:27 1999
            Repository revision: 1.2     /usr/local/cvs/myproj/b-subdir/random.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

The Working revision and Repository revision tell you whether the file is out of sync with the repository. Returning to our original working copy (jrandom's copy, which hasn't seen the new change to hello.c yet), we see:

         floss$ cvs status hello.c
         ===================================================================
         File: hello.c           Status: Needs Patch

            Working revision:    1.2     Mon Apr 19 02:17:07 1999
            Repository revision: 1.3     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         floss$

This tells us that someone has committed a change to hello.c, bringing the repository copy to revision 1.3, but that this working copy is still on revision 1.2. The line Status: Needs Patch means that the next update will retrieve those changes from the repository and "patch" them into the working copy's file.

Let's pretend for the moment that we don't know anything about qsmith's change to hello.c, so we don't run status or update. Instead, we just start editing the file, making a slightly different change at the same location. This brings us to our first conflict.

Node: Detecting And Resolving Conflicts, Next: Finding Out Who Did What (Browsing Log Messages), Previous: Revision Numbers, Up: A Day With CVS

### Detecting And Resolving Conflicts

Detecting a conflict is easy enough. When you run update, CVS tells you, in no uncertain terms, that there's a conflict. But first, let's create the conflict. We edit hello.c to insert the line

         printf ("this change will conflict\n");

right where qsmith committed this:

         printf ("between hello and goodbye\n");

At this point, the status of our copy of hello.c is

         floss$ cvs status hello.c
         ===================================================================
         File: hello.c           Status: Needs Merge

            Working revision:    1.2     Mon Apr 19 02:17:07 1999
            Repository revision: 1.3     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:          (none)
            Sticky Date:         (none)
            Sticky Options:      (none)

         floss$

meaning that there are changes both in the repository and the working copy, and these changes need to be merged. (CVS isn't aware that the changes will conflict, because we haven't run update yet.) When we do the update, we see this:

         floss$ cvs update hello.c
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.2
         retrieving revision 1.3
         Merging differences between 1.2 and 1.3 into hello.c
         rcsmerge: warning: conflicts during merge
         cvs update: conflicts found in hello.c
         C hello.c
         floss$

The last line of output is the giveaway. The C in the left margin next to the filename indicates that changes have been merged, but that they conflict. The contents of hello.c now shows both changes:

         #include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
         <<<<<<< hello.c
           printf ("this change will conflict\n");
         =======
           printf ("between hello and goodbye\n");
         >>>>>>> 1.3
           printf ("Goodbye, world!\n");
         }

Conflicts are always shown delimited by conflict markers, in the following format:

         <<<<<<< (filename)
           the uncommitted changes in the working copy
           blah blah blah
         =======
           the new changes that came from the repository
           blah blah blah
           and so on
         >>>>>>> (latest revision number in the repository)

The Entries file also shows that the file is in a halfway state at the moment:

         floss$ cat CVS/Entries
         /README.txt/1.1.1.1/Sun Apr 18 18:18:22 1999//
         D/a-subdir////
         D/b-subdir////
         /hello.c/1.3/Result of merge+Tue Apr 20 03:59:09 1999//
         floss$

The way to resolve the conflict is to edit the file so that it contains whatever text is appropriate, removing the conflict markers in the process, and then to commit. This doesn't necessarily mean choosing one change over another; you could decide neither change is sufficient and rewrite the conflicting section (or indeed the whole file) completely. In this case, we'll adjust in favor of the first change, but with capitalization and punctuation slightly different from qsmith's:

         floss$ emacs hello.c
           (make the edits...)
         floss$ cat hello.c
         #include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
           printf ("BETWEEN HELLO AND GOODBYE.\n");
           printf ("Goodbye, world!\n");
         }
         floss$ cvs ci -m "adjusted middle line"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <-  hello.c
         new revision: 1.4; previous revision: 1.3
         done
         floss$

Node: Finding Out Who Did What (Browsing Log Messages), Next: Examining And Reverting Changes, Previous: Detecting And Resolving Conflicts, Up: A Day With CVS

### Finding Out Who Did What (Browsing Log Messages)

By now, the project has undergone several changes. If you're trying to get an overview of what has happened so far, you don't necessarily want to examine every diff in detail. Browsing the log messages would be ideal, and you can accomplish this with the log command:

         floss$ cvs log
         (pages upon pages of output omitted)

The log output tends to be a bit verbose. Let's look at the log messages for just one file:

         floss$ cvs log hello.c
         RCS file: /usr/local/cvs/myproj/hello.c,v
         Working file: hello.c
         head: 1.4
         branch:
         locks: strict
         access list:
         symbolic names:
                 start: 1.1.1.1
                 jrandom: 1.1.1
         keyword substitution: kv
         total revisions: 5;     selected revisions: 5
         description:
         --------------
         revision 1.4
         date: 1999/04/20 04:14:37;  author: jrandom;  state: Exp;  lines: +1 -1
         adjusted middle line
         --------------
         revision 1.3
         date: 1999/04/20 02:30:05;  author: qsmith;  state: Exp;  lines: +1 -0
         added new middle line
         --------------
         revision 1.2
         date: 1999/04/19 06:35:15;  author: jrandom;  state: Exp;  lines: +1 -0
         print goodbye too
         --------------
         revision 1.1
         date: 1999/04/18 18:18:22;  author: jrandom;  state: Exp;
         branches:  1.1.1;
         Initial revision
         --------------
         revision 1.1.1.1
         date: 1999/04/18 18:18:22;  author: jrandom;  state: Exp;  lines: +0 -0
         initial import into CVS
         =========================================================================
         floss$

As usual, there's a lot of information at the top that you can just ignore. The good stuff comes after each line of dashes, in a format that is self-explanatory.

When many files are sent in the same commit, they all share the same log message; a fact that can be useful in tracing changes. For example, remember back when we committed fish.c and random.c simultaneously? It was done like this:

         floss$ cvs commit -m "filled out C code"
         Checking in a-subdir/subsubdir/fish.c;
         /usr/local/cvs/myproj/a-subdir/subsubdir/fish.c,v  <-  fish.c
         new revision: 1.2; previous revision: 1.1
         done
         Checking in b-subdir/random.c;
         /usr/local/cvs/myproj/b-subdir/random.c,v  <-  random.c
         new revision: 1.2; previous revision: 1.1
         done
         floss$

The effect of this was to commit both files with the same log message: "Filled out C code." (As it happened, both files started at revision 1.1 and went to 1.2, but that's just a coincidence. If random.c had been at revision 1.29, it would have moved to 1.30 with this commit, and its revision 1.30 would have had the same log message as fish.c's revision 1.2.)

When you run cvs log on them, you'll see the shared message:

         floss$ cvs log a-subdir/subsubdir/fish.c b-subdir/random.c

         RCS file: /usr/local/cvs/myproj/a-subdir/subsubdir/fish.c,v
         Working file: a-subdir/subsubdir/fish.c
         head: 1.2
         branch:
         locks: strict
         access list:
         symbolic names:
                 start: 1.1.1.1
                 jrandom: 1.1.1
         keyword substitution: kv
         total revisions: 3;     selected revisions: 3
         description:
         --------------
         revision 1.2
         date: 1999/04/19 06:35:27;  author: jrandom;  state: Exp;  lines: +8 -1
         filled out C code
         --------------
         revision 1.1
         date: 1999/04/18 18:18:22;  author: jrandom;  state: Exp;
         branches:  1.1.1;
         Initial revision
         --------------
         revision 1.1.1.1
         date: 1999/04/18 18:18:22;  author: jrandom;  state: Exp;  lines: +0 -0
         initial import into CVS
         =========================================================================
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         Working file: b-subdir/random.c
         head: 1.2
         branch:
         locks: strict
         access list:
         symbolic names:
                 start: 1.1.1.1
                 jrandom: 1.1.1
         keyword substitution: kv
         total revisions: 3;     selected revisions: 3
         description:
         --------------
         revision 1.2
         date: 1999/04/19 06:35:27;  author: jrandom;  state: Exp;  lines: +8 -1
         filled out C code
         --------------
         revision 1.1
         date: 1999/04/18 18:18:22;  author: jrandom;  state: Exp;
         branches:  1.1.1;
         Initial revision
         --------------
         revision 1.1.1.1
         date: 1999/04/18 18:18:22;  author: jrandom;  state: Exp;  lines: +0 -0
         initial import into CVS
         =========================================================================
         floss$

From this output, you'll know that the two revisions were part of the same commit (the fact that the timestamps on the two revisions are the same, or very close, is further evidence).

Browsing log messages is a good way to get a quick overview of what's been going on in a project or to find out what happened to a specific file at a certain time. There are also free tools available to convert raw cvs log output to more concise and readable formats (such as GNU ChangeLog style); we won't cover those tools in this tour, but they'll be introduced in Third-Party Tools.

Node: Examining And Reverting Changes, Next: The Slow Method Of Reverting, Previous: Finding Out Who Did What (Browsing Log Messages), Up: A Day With CVS

### Examining And Reverting Changes

Suppose that, in the course of browsing the logs, qsmith sees that jrandom made the most recent change to hello.c:

         revision 1.4
         date: 1999/04/20 04:14:37;  author: jrandom;  state: Exp;  lines: +1 -1
         adjusted middle line

and wonders what jrandom did? In formal terms, the question that qsmith is asking is, "What's the difference between my revision (1.3) of hello.c, and jrandom's revision right after it (1.4)?" The way to find out is with the diff command, but this time by comparing two past revisions using the -r command option to specify both of them:

         paste$ cvs diff -c -r 1.3 -r 1.4 hello.c
         Index: hello.c
         ===========================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.3
         retrieving revision 1.4
         diff -c -r1.3 -r1.4
         *** hello.c     1999/04/20 02:30:05     1.3
         --- hello.c     1999/04/20 04:14:37     1.4
         ***************
         *** 4,9 ****
           main ()
           {
             printf ("Hello, world!\n");
         !   printf ("between hello and goodbye\n");
             printf ("Goodbye, world!\n");
           }
         --- 4,9 --
           main ()
           {
             printf ("Hello, world!\n");
         !   printf ("BETWEEN HELLO AND GOODBYE.\n");
             printf ("Goodbye, world!\n");
           }
         paste$

The change is pretty clear, when viewed this way. Because the revision numbers are given in chronological order (usually a good idea), the diff shows them in order. If only one revision number is given, CVS uses the revision of the current working copy for the other.

When qsmith sees this change, he instantly decides he likes his way better and resolves to "undo"-that is, to step back by one revision.

However, this doesn't mean that he wants to lose his revision 1.4. Although, in an absolute technical sense, it's probably possible to achieve that effect in CVS, there's almost never any reason to do so. It's much preferable to keep revision 1.4 in the history and make a new revision 1.5 that looks exactly like 1.3. That way the undo event itself is part of the file's history.

The only question is, how can you retrieve the contents of revision 1.3 and put them into 1.5?

In this particular case, because the change is a very simple one, qsmith can probably just edit the file by hand to mirror revision 1.3 and then commit. However, if the changes are more complex (as they usually are in a real-life project), trying to re-create the old revision manually will be hopelessly error-prone. Therefore, we'll have qsmith use CVS to retrieve and recommit the older revision's contents.

There are two equally good ways to do this: the slow, plodding way and the fast, fancy way. We'll examine the slow, plodding way first.

Node: The Slow Method Of Reverting, Next: The Fast Method Of Reverting, Previous: Examining And Reverting Changes, Up: A Day With CVS

### The Slow Method Of Reverting

This method involves passing the -p flag to update, in conjunction with -r. The -p option sends the contents of the named revision to standard output. By itself, this isn't terribly helpful; the contents of the file fly by on the display, leaving the working copy unchanged. However, by redirecting the standard output into the file, the file will now hold the contents of the older revision. It's just as though the file had been hand-edited into that state.

First, though, qsmith needs to get up to date with respect to the repository:

         paste$ cvs update
         cvs update: Updating .
         U hello.c
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         paste$ cat hello.c
         #include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
           printf ("BETWEEN HELLO AND GOODBYE.\n");
           printf ("Goodbye, world!\n");
         }
         paste$

Next, he runs update -p to make sure that the revision 1.3 is the one he wants:

         paste$ cvs update -p -r 1.3 hello.c
         ===================================================================
         Checking out hello.c
         RCS:  /usr/local/cvs/myproj/hello.c,v
         VERS: 1.3
         ***************
         #include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
           printf ("between hello and goodbye\n");
           printf ("Goodbye, world!\n");
         }

Oops, there are a few lines of cruft at the beginning. They aren't actually being sent to standard output, but rather to standard error, so they're harmless. Nevertheless, they make reading the output more difficult and can be suppressed with -Q:

         paste$ cvs -Q update -p -r 1.3 hello.c
         #include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
           printf ("between hello and goodbye\n");
           printf ("Goodbye, world!\n");
         }
         paste$

There - that's exactly what qsmith was hoping to retrieve. The next step is to put that content into the working copy's file, using a Unix redirect (that's what the ">" does):

         paste$ cvs -Q update -p -r 1.3 hello.c > hello.c
         paste$ cvs update
         cvs update: Updating .
         M hello.c
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         paste$

Now when update is run, the file is listed as modified, which makes sense because its contents have changed. Specifically, it has the same content as the old revision 1.3 (not that CVS is aware of its being identical to a previous revision - it just knows the file has been modified). If qsmith wants to make extra sure, he can do a diff to check:

         paste$ cvs -Q diff -c
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.4
         diff -c -r1.4 hello.c
         *** hello.c     1999/04/20 04:14:37     1.4
         --- hello.c     1999/04/20 06:02:25
         ***************
         *** 4,9 ****
           main ()
           {
             printf ("Hello, world!\n");
         !   printf ("BETWEEN HELLO AND GOODBYE.\n");
             printf ("Goodbye, world!\n");
           }
         --- 4,9 --
           main ()
           {
             printf ("Hello, world!\n");
         !   printf ("between hello and goodbye\n");
             printf ("Goodbye, world!\n");
           }
         paste$

Yes, that's exactly what he wanted: a pure reversion - in fact, it is the reverse of the diff he previously obtained. Satisfied, he commits:

         paste$ cvs ci -m "reverted to 1.3 code"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <-  hello.c
         new revision: 1.5; previous revision: 1.4
         done
         paste$

Node: The Fast Method Of Reverting, Previous: The Slow Method Of Reverting, Up: A Day With CVS

### The Fast Method Of Reverting

The fast, fancy way of reverting is to use the -j (for "join") flag to the update command. This flag is like -r in that it takes a revision number, and you can use up to two -j's at once. CVS calculates the difference between the two named revisions and applies that difference as a patch to the file in question (so the order in which you give the revisions is important).

Thus, assuming qsmith's copy is up to date, he can just do this:

         paste$ cvs update -j 1.4 -j 1.3 hello.c
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.4
         retrieving revision 1.3
         Merging differences between 1.4 and 1.3 into hello.c
         paste$ cvs update
         cvs update: Updating .
         M hello.c
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         paste$ cvs ci -m "reverted to 1.3 code" hello.c
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <--  hello.c
         new revision: 1.5; previous revision: 1.4
         done
         paste$

When you only need to revert one file, there's not really much difference between the plodding and fast methods. Later in the book, you'll see how the fast method is much better for reverting multiple files at once. In the meantime, use whichever way you're more comfortable with.

### Reverting Is Not A Substitute For Communication

In all likelihood, what qsmith did in our example was quite rude. When you're working on a real project with other people and you think that someone has committed a bad change, the first thing you should do is talk to him or her about it. Maybe there's a good reason for the change, or maybe he or she just didn't think things through. Either way, there's no reason to rush and revert. A full record of everything that happens is stored permanently in CVS, so you can always revert to a previous revision after consulting with whoever made the changes.

If you're a project maintainer facing a deadline or you feel you have the right and the need to revert the change unconditionally, then do so - but follow it immediately with an email to the author whose change was reverted, explaining why you did it and what needs to be fixed to recommit the change.

Node: Other Useful CVS Commands, Next: Branches, Previous: A Day With CVS, Up: An Overview of CVS

### Other Useful CVS Commands

At this point, you should be pretty comfortable with basic CVS usage. I'll abandon the tour narrative and introduce a few more useful commands in summarized form.

Node: Adding Files, Next: Adding Directories, Up: Other Useful CVS Commands

### Adding Files

Adding a file is a two-step process: First you run the add command on it, then commit. The file won't actually appear in the repository until commit is run:

         floss$ cvs add newfile.c
         cvs add: scheduling file 'newfile.c' for addition
         cvs add: use 'cvs commit' to add this file permanently
         floss$ cvs ci -m "added newfile.c" newfile.c
         RCS file: /usr/local/cvs/myproj/newfile.c,v
         done
         Checking in newfile.c;
         /usr/local/cvs/myproj/newfile.c,v  <-  newfile.c
         initial revision: 1.1
         done
         floss$

Node: Adding Directories, Next: CVS And Binary Files, Previous: Adding Files, Up: Other Useful CVS Commands

### Adding Directories

Unlike adding a file, adding a new directory is done in one step; there's no need to do a commit afterwards:

         floss$ mkdir c-subdir
         floss$ cvs add c-subdir
         Directory /usr/local/cvs/myproj/c-subdir added to the repository
         floss$

If you look inside the new directory in the working copy, you'll see that a CVS subdirectory was created automatically by add:

         floss$ ls c-subdir
         CVS/
         floss$ ls c-subdir/CVS
         Entries     Repository  Root
         floss$

Now you can add files (or new directories) inside it, as with any other working copy directory.

Node: CVS And Binary Files, Next: Removing Files, Previous: Adding Directories, Up: Other Useful CVS Commands

### CVS And Binary Files

Until now, I've left unsaid the dirty little secret of CVS, which is that it doesn't handle binary files very well (well, there are other dirty little secrets, but this definitely counts as one of the dirtiest). It's not that CVS doesn't handle binaries at all; it does, just not with any great panache.

All the files we've been working with until now have been plain text files. CVS has some special tricks for text files. For example, when it's working between a Unix repository and a Windows or Macintosh working copy, it converts file line endings appropriately for each platform. For example, Unix convention is to use a linefeed (LF) only, whereas Windows expects a carriage return/linefeed (CRLF) sequence at the end of each line. Thus, the files in a working copy on a Windows machine will have CRLF endings, but a working copy of the same project on a Unix machine will have LF endings (the repository itself is always stored in LF format).

Another trick is that CVS detects special strings, known as RCS keyword strings, in text files and replaces them with revision information and other useful things. For example, if your file contains this string

         $Revision$

CVS will expand on each commit to include the revision number. For example, it may get expanded to

         $Revision: 1.3 $

CVS will keep that string up to date as the file is developed. (The various keyword strings are documented in Advanced CVS and Third-Party Tools.)

This string expansion is a very useful feature in text files, as it allows you to see the revision number or other information about a file while you're editing it. But what if the file is a JPG image? Or a compiled executable program? In those kinds of files, CVS could do some serious damage if it blundered around expanding any keyword string that it encountered. In a binary, such strings may even appear by coincidence.

Therefore, when you add a binary file, you have to tell CVS to turn off both keyword expansion and line-ending conversion. To do so, use -kb:

         floss$ cvs add -kb filename
         floss$ cvs ci -m "added blah" filename
           (etc)

Also, in some cases (such as text files that are likely to contain spurious keyword strings), you may wish to disable just the keyword expansion. That's done with -ko:

         floss$ cvs add -ko filename
         floss$ cvs ci -m "added blah" filename
           (etc)

(In fact, this chapter is one such document, because of the `$Revision$` example shown here.)

Note that you can't meaningfully run `cvs diff` on two revisions of a binary file. Diff uses a text-based algorithm that can only report whether two binary files differ, but not how they differ. Future versions of CVS may provide a way to diff binary files.

Node: Removing Files, Next: Removing Directories, Previous: CVS And Binary Files, Up: Other Useful CVS Commands

### Removing Files

Removing a file is similar to adding one, except there's an extra step: You have to remove the file from the working copy first:

         floss$ rm newfile.c
         floss$ cvs remove newfile.c
         cvs remove: scheduling 'newfile.c' for removal
         cvs remove: use 'cvs commit' to remove this file permanently
         floss$ cvs ci -m "removed newfile.c" newfile.c
         Removing newfile.c;
         /usr/local/cvs/myproj/newfile.c,v  <-  newfile.c
         new revision: delete; previous revision: 1.1
         done
         floss$

Notice how, in the second and third commands, we name newfile.c explicitly even though it doesn't exist in the working copy anymore. Of course, in the commit, you don't absolutely need to name the file, as long as you don't mind the commit encompassing any other modifications that may have taken place in the working copy.

Node: Removing Directories, Next: Renaming Files And Directories, Previous: Removing Files, Up: Other Useful CVS Commands

### Removing Directories

As I said before, CVS doesn't really keep directories under version control. Instead, as a kind of cheap substitute, it offers certain odd behaviors that in most cases do the "right thing". One of these odd behaviors is that empty directories can be treated specially. If you want to remove a directory from a project, you first remove all the files in it

         floss$ cd dir
         floss$ rm file1 file2 file3
         floss$ cvs remove file1 file2 file3
           (output omitted)
         floss$ cvs ci -m "removed all files" file1 file2 file3
           (output omitted)

and then run update in the directory above it with the -P flag:

         floss$ cd ..
         floss$ cvs update -P
           (output omitted)

The -P option tells update to "prune" any empty directories - that is, to remove them from the working copy. Once that's done, the directory can be said to have been removed; all of its files are gone, and the directory itself is gone (from the working copy, at least, although there is actually still an empty directory in the repository).

An interesting counterpart to this behavior is that when you run a plain update, CVS does not automatically bring new directories from the repository into your working copy. There are a couple of different justifications for this, none really worth going into here. The short answer is that from time to time you should run update with the -d flag, telling it to bring down any new directories from the repository.

Node: Renaming Files And Directories, Next: Avoiding Option Fatigue, Previous: Removing Directories, Up: Other Useful CVS Commands

### Renaming Files And Directories

Renaming a file is equivalent to creating it under the new name and removing it under the old. In Unix, the commands are:

         floss$ cp oldname newname
         floss$ rm oldname

Here's the equivalent in CVS:

         floss$ mv oldname newname
         floss$ cvs remove oldname
           (output omitted)
         floss$ cvs add newname
           (output omitted)
         floss$ cvs ci -m "renamed oldname to newname" oldname newname
           (output omitted)
         floss$

For files, that's all there is to it. Renaming directories is not done very differently: create the new directory, cvs add it, move all the files from the old directory to the new one, cvs remove them from the old directory, cvs add them in the new one, cvs commit so everything takes effect, and then do cvs update -P to make the now-empty directory disappear from the working copy. That is to say:

         floss$ mkdir newdir
         floss$ cvs add newdir
         floss$ mv olddir/* newdir
         mv: newdir/CVS: cannot overwrite directory
         floss$ cd olddir
         floss$ cvs rm foo.c bar.txt
         floss$ cd ../newdir
         floss$ cvs add foo.c bar.txt
         floss$ cd ..
         floss$ cvs commit -m "moved foo.c and bar.txt from olddir to newdir"
         floss$ cvs update -P

Note: the warning message after the third command. It's telling you that it can't copy olddir's CVS/ subdirectory into newdir because newdir already has a directory of that name. This is fine, because you want olddir to keep its CVS/ subdirectory anyway.

Obviously, moving directories around can get a bit cumbersome. The best policy is to try to come up with a good layout when you initially import your project so you won't have to move directories around very often. Later, you'll learn about a more drastic method of moving directories that involves making the change directly in the repository. However, that method is best saved for emergencies; whenever possible, it's best to handle everything with CVS operations inside working copies.

Node: Avoiding Option Fatigue, Next: Getting Snapshots (Dates And Tagging), Previous: Renaming Files And Directories, Up: Other Useful CVS Commands

### Avoiding Option Fatigue

Most people tire pretty quickly of typing the same option flags with every command. If you know that you always want to pass the -Q global option or you always want to use -c with diff, why should you have to type it out each time?

There is help, fortunately. CVS looks for a .cvsrc file in your home directory. In that file, you can specify default options to apply to every invocation of CVS. Here's an example .cvsrc:

         diff -c
         update -P
         cvs -q

If the leftmost word on a line matches a CVS command (in its unabbreviated form), the corresponding options are used for that command every time. For global options, you just use cvs. So, for example, every time that user runs cvs diff, the -c flag is automatically included.

Node: Getting Snapshots (Dates And Tagging), Next: Acceptable Date Formats, Previous: Avoiding Option Fatigue, Up: Other Useful CVS Commands

### Getting Snapshots (Dates And Tagging)

Let's return to the example of the program that's in a broken state when a bug report comes in. The developer suddenly needs access to the entire project as it was at the time of the last release, even though many files may have been changed since then, and each file's revision number differs from the others. It would be far too time-consuming to look over the log messages, figure out what each file's individual revision number was at the time of release, and then run update (specifying a revision number with -r) on each one of them. In medium- to large-sized projects (tens to hundreds of files), such a process would be too unwieldy to attempt.

CVS, therefore, provides a way to retrieve previous revisions of the files in a project en masse. In fact, it provides two ways: by date, which selects the revisions based on the time that they were committed, and by tag, which retrieves a previously marked "snapshot" of the project.

Which method you use depends on the situation. The date-based retrievals are done by passing update the -D flag, which is similar to -r but takes dates instead of revision numbers:

         floss$ cvs -q update -D "1999-04-19"
         U hello.c
         U a-subdir/subsubdir/fish.c
         U b-subdir/random.c
         floss$

With the -D option, update retrieves the highest revision of each file as of the given date, and it will revert the files in the working copy to prior revisions if necessary.

When you give the date, you can, and often should, include the time. For example, the previous command ended up retrieving revision 1.1 of everything (only three files showed changes, because all of the others are still at revision 1.1 anyway). Here's the status of hello.c to prove it:

         floss$ cvs -Q status hello.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:          1.1.1.1 Sat Apr 24 22:45:03 1999
            Repository revision:       1.1.1.1 /usr/local/cvs/myproj/hello.c,v
            Sticky Date:               99.04.19.05.00.00
         floss$

But a glance back at the log messages from earlier in this chapter shows that revision 1.2 of hello.c was definitely committed on April 19, 1999. So why did we now get revision 1.1 instead of 1.2?

The problem is that the date "1999-04-19" was interpreted as meaning "the midnight that begins 1999-04-19" - that is, the very first instant on that date. This is probably not what you want. The 1.2 commit took place later in the day. By qualifying the date more precisely, we can retrieve revision 1.2:

         floss$ cvs -q update -D "1999-04-19 23:59:59"
         U hello.c
         U a-subdir/subsubdir/fish.c
         U b-subdir/random.c
         floss$ cvs status hello.c
         ===================================================================
         File: hello.c                 Status: Locally Modified
            Working revision:  1.2     Sat Apr 24 22:45:22 1999
            Repository revision:       1.2     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                (none)
            Sticky Date:               99.04.20.04.59.59
            Sticky Options:    (none)
         floss$

We're almost there. If you look closely at the date/time on the Sticky Date line, it seems to indicate 4:59:59 A.M., not 11:59 as the command requested (later we'll get to what the "sticky" means). As you may have guessed, the discrepancy is due to the difference between local time and Universal Coordinated Time (also known as "Greenwich mean time"). The repository always stores dates in Universal Time, but CVS on the client side usually assumes the local system time zone. In the case of -D, this is rather unfortunate because you're probably most interested in comparing against the repository time and don't care about the local system's idea of time. You can get around this by specifying the GMT zone in the command:

         floss$ cvs -q update -D "1999-04-19 23:59:59 GMT"
         U hello.c
         floss$ cvs -q status hello.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:  1.2     Sun Apr 25 22:38:53 1999
            Repository revision:       1.2     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                (none)
            Sticky Date:               99.04.19.23.59.59
            Sticky Options:    (none)
         floss$

There - that brought the working copy back to the final commits from April 19 (unless there were any commits during the last second of the day, which there weren't).

What happens now if you run update?

         floss$ cvs update
         cvs update: Updating .
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         floss$

Nothing happens at all. But you know that there are more recent versions of at least three files. Why aren't these included in your working copy?

That's where the "sticky" comes in. Updating ("downdating"?) with the -D flag causes the working copy to be restricted permanently to that date or before. In CVS terminology, the working copy has a "sticky date" set. Once a working copy has acquired a sticky property, it stays sticky until told otherwise. Therefore, subsequent updates will not automatically retrieve the most recent revision. Instead, they'll stay restricted to the sticky date. Stickiness can be revealed by running cvs status or by directly examining the CVS/Entries file:

         floss$ cvs -q update -D "1999-04-19 23:59:59 GMT"
         U hello.c
         floss$ cat CVS/Entries
         D/a-subdir////
         D/b-subdir////
         D/c-subdir////
         /README.txt/1.1.1.1/Sun Apr 18 18:18:22 1999//D99.04.19.23.59.59
         /hello.c/1.2/Sun Apr 25 23:07:29 1999//D99.04.19.23.59.59
         floss$

If you were to modify hello.c and then try to commit

         floss$ cvs update
         M hello.c
         floss$ cvs ci -m "trying to change the past"
         cvs commit: cannot commit with sticky date for file 'hello.c'
         cvs [commit aborted]: correct above errors first!
         floss$

CVS would not permit the commit to happen because that would be like allowing you to go back and change the past. CVS is all about record keeping and, therefore, will not allow you to do that.

This does not mean CVS is unaware of all the revisions that have been committed since that date, however. You can still compare the sticky-dated working copy against other revisions, including future ones:

         floss$ cvs -q diff -c -r 1.5 hello.c
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.5
         diff -c -r1.5 hello.c
         *** hello.c   1999/04/24 22:09:27     1.5
         --- hello.c   1999/04/25 00:08:44
         ***************
         *** 3,9 ****
           void
           main ()
           {
             printf ("Hello, world!\n");
         -   printf ("between hello and goodbye\n");
             printf ("Goodbye, world!\n");
           }
         --- 3,9 --
           void
           main ()
           {
         +   /* this line was added to a downdated working copy */
             printf ("Hello, world!\n");
             printf ("Goodbye, world!\n");
           }

This diff reveals that, as of April 19, 1999, the between hello and goodbye line had not yet been added. It also shows the modification that we made to the working copy (adding the comment shown in the preceding code snippet).

You can remove a sticky date (or any sticky property) by updating with the -A flag (-A stands for "reset", don't ask me why), which brings the working copy back to the most recent revisions:

         floss$ cvs -q update -A
         U hello.c
         floss$ cvs status hello.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:  1.5     Sun Apr 25 22:50:27 1999
            Repository revision:       1.5     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                (none)
            Sticky Date:               (none)
            Sticky Options:    (none)
         floss$

Node: Acceptable Date Formats, Next: Marking A Moment In Time (Tags), Previous: Getting Snapshots (Dates And Tagging), Up: Other Useful CVS Commands

### Acceptable Date Formats

CVS accepts a wide range of syntaxes to specify dates. You'll never go wrong if you use ISO 8601 format (that is, the International Standards Organization standard #8601, see also www.saqqara.demon.co.uk/datefmt.htm), which is the format used in the preceding examples. You can also use Internet email dates as described in RFC 822 and RFC 1123 (see www.rfc-editor.org/rfc/). Finally, you can use certain unambiguous English constructs to specify dates relative to the current date.

You will probably never need all of the formats available, but here are some more examples to give you an idea of what CVS accepts:

         floss$ cvs update -D "19 Apr 1999"
         floss$ cvs update -D "19 Apr 1999 20:05"
         floss$ cvs update -D "19/04/1999"
         floss$ cvs update -D "3 days ago"
         floss$ cvs update -D "5 years ago"
         floss$ cvs update -D "19 Apr 1999 23:59:59 GMT"
         floss$ cvs update -D "19 Apr"

The double quotes around the dates are there to ensure that the Unix shell treats the date as one argument even if it contains spaces. The quotes will do no harm if the date doesn't contain spaces, so it's probably best to always use them.

Node: Marking A Moment In Time (Tags), Previous: Acceptable Date Formats, Up: Other Useful CVS Commands

### Marking A Moment In Time (Tags)

Retrieving by date is useful when the mere passage of time is your main concern. But more often what you really want to do is retrieve the project as it was at the time of a specific event - perhaps a public release, a known stable point in the software's development, or the addition or removal of some major feature.

Trying to remember the date when that event took place or deducing the date from log messages would be a tedious process. Presumably, the event, because it was important, was marked as such in the formal revision history. The method CVS offers for making such marks is known as tagging.

Tags differ from commits in that they don't record any particular textual change to files, but rather a change in the developers' attitude about the files. A tag gives a label to the collection of revisions represented by one developer's working copy (usually, that working copy is completely up to date so the tag name is attached to the "latest and greatest" revisions in the repository).

Setting a tag is as simple as this:

         floss$ cvs -q tag Release-1999_05_01
         T README.txt
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         floss$

That command associates the symbolic name "Release-1999_05_01" with the snapshot represented by this working copy. Defined formally, snapshot means a set of files and associated revision numbers from the project. Those revision numbers do not have to be the same from file to file and, in fact, usually aren't. For example, assuming that tag was done on the same myproj directory that we've been using throughout this chapter and that the working copy was completely up to date, the symbolic name "Release-1999_05_01" will be attached to hello.c at revision 1.5, to fish.c at revision 1.2, to random.c at revision 1.2, and to everything else at revision 1.1.

It may help to visualize a tag as a path or string linking various revisions of files in the project. In Figure 2.1, an imaginary string passes through the tagged revision number of each file in a project.

              File A      File B      File C      File D      File E
              ------      ------      ------      ------      ------
              1.1         1.1         1.1         1.1         1.1
          ----1.2-.       1.2         1.2         1.2         1.2
              1.3 |       1.3         1.3         1.3         1.3
                   \      1.4       .-1.4-.       1.4         1.4
                    \     1.5      /  1.5  \      1.5         1.5
                     \    1.6     /   1.6   |     1.6         1.6
                      \   1.7    /          |     1.7         1.7
                       \  1.8   /           |     1.8       .-1.8------->
                        \ 1.9  /            |     1.9      /  1.9
                         `1.10'             |     1.10    /   1.10
                          1.11              |     1.11    |
                                            |     1.12    |
                                            |     1.13    |
                                             \    1.14    |
                                              \   1.15   /
                                               \  1.16  /
                                                `-1.17-'

         [Figure 2.1: How a tag might stand in relation to files's revisions.]

But if you pull the string taut and sight directly along it, you'll see a particular moment in the project's history - namely, the moment that the tag was set (Figure 2.2).

              File A      File B      File C      File D      File E
              ------      ------      ------      ------      ------
                                                  1.1
                                                  1.2
                                                  1.3
                                                  1.4
                                                  1.5
                                                  1.6
                                                  1.7
                          1.1                     1.8
                          1.2                     1.9
                          1.3                     1.10        1.1
                          1.4                     1.11        1.2
                          1.5                     1.12        1.3
                          1.6                     1.13        1.4
                          1.7         1.1         1.14        1.5
                          1.8         1.2         1.15        1.6
              1.1         1.9         1.3         1.16        1.7
          ----1.2---------1.10--------1.4---------1.17--------1.8------->
              1.3         1.11        1.5         1.17        1.9
                                      1.6         1.17        1.10

         [Figure 2.2: The same tag as a "straight sight" through the revision history.]

As you continue to edit files and commit changes, the tag will not move along with the increasing revision numbers. It stays fixed, "stickily", at the revision number of each file at the time the tag was made.

Given their importance as descriptors, it's a bit unfortunate that log messages can't be included with tags or that the tags themselves can't be full paragraphs of prose. In the preceding example, the tag is fairly obviously stating that the project was in a releasable state as of a certain date. However, sometimes you may want to make snapshots of a more complex state, which can result in ungainly tag names such as:

         floss$ cvs tag testing-release-3_pre-19990525-public-release

As a general rule, you should try to keep tags as terse as possible while still including all necessary information about the event that you're trying to record. When in doubt, err on the side of being overly descriptive - you'll be glad later when you're able to tell from some verbose tag name exactly what circumstance was recorded.

You've probably noticed that no periods or spaces were used in the tag names. CVS is rather strict about what constitutes a valid tag name. The rules are that it must start with a letter and contain letters, digits, hyphens ("-"), and underscores ("_"). No spaces, periods, colons, commas, or any other symbols may be used.

To retrieve a snapshot by tag name, the tag name is used just like a revision number. There are two ways to retrieve snapshots: You can check out a new working copy with a certain tag, or you can switch an existing working copy over to a tag. Both result in a working copy whose files are at the revisions specified by the tag.

Most of the time, what you're trying to do is take a look at the project as it was at the time of the snapshot. You may not necessarily want to do this in your main working copy, where you presumably have uncommitted changes and other useful states built up, so let's assume you just want to check out a separate working copy with the tag. Here's how (but make sure to invoke this somewhere other than in your existing working copy or its parent directory!):

         floss$ cvs checkout -r Release-1999_05_01 myproj
         cvs checkout: Updating myproj
         U myproj/README.txt
         U myproj/hello.c
         cvs checkout: Updating myproj/a-subdir
         U myproj/a-subdir/whatever.c
         cvs checkout: Updating myproj/a-subdir/subsubdir
         U myproj/a-subdir/subsubdir/fish.c
         cvs checkout: Updating myproj/b-subdir
         U myproj/b-subdir/random.c
         cvs checkout: Updating myproj/c-subdir

We've seen the -r option before in the update command, where it preceded a revision number. In many ways a tag is just like a revision number because, for any file, a given tag corresponds to exactly one revision number (it's illegal, and generally impossible, to have two tags of the same name in the same project). In fact, anywhere you can use a revision number as part of a CVS command, you can use a tag name instead (as long as the tag has been set previously). If you want to diff a file's current state against its state at the time of the last release, you can do this:

         floss$ cvs diff -c -r Release-1999_05_01 hello.c

And if you want to revert it temporarily to that revision, you can do this:

         floss$ cvs update -r Release-1999_05_01 hello.c

The interchangeability of tags and revision numbers explains some of the strict rules about valid tag names. Imagine if periods were legal in tag names; you could have a tag named "1.3" attached to an actual revision number of "1.47". If you then issued the command

         floss$ cvs update -r 1.3 hello.c

how would CVS know whether you were referring to the tag named "1.3", or the much earlier revision 1.3 of hello.c? Thus, restrictions are placed on tag names so that they can always be easily distinguished from revision numbers. A revision number has a period; a tag name doesn't. (There are reasons for the other restrictions, too, mostly having to do with making tag names easy for CVS to parse.)

As you've probably guessed by this point, the second method of retrieving a snapshot - that is, switching an existing working directory over to the tagged revisions-is also done by updating:

         floss$ cvs update -r Release-1999_05_01
         cvs update: Updating .
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         cvs update: Updating c-subdir
         floss$

The preceding command is just like the one we used to revert hello.c to `Release-1999_05_01`, except that the filename is omitted because we want to revert the entire project over. (You can, if you want, revert just one subtree of the project to the tag by invoking the preceding command in that subtree instead of from the top level, although you hardly ever would want to do that.)

Note that no files appear to have changed when we updated. The working copy was completely up to date when we tagged, and no changes had been committed since the tagging.

However, this does not mean that nothing changed at all. The working copy now knows that it's at a tagged revision. When you make a change and try to commit it (let's assume we modified hello.c):

         floss$ cvs -q update
         M hello.c
         floss$ cvs -q ci -m "trying to commit from a working copy on a tag"
         cvs commit: sticky tag 'Release-1999_05_01' for file 'hello.c' is not a branch
         cvs [commit aborted]: correct above errors first!
         floss$

CVS does not permit the commit to happen. (Don't worry about the exact meaning of that error message yet - we'll cover branches next in this chapter.) It doesn't matter whether the working copy got to be on a tag via a checkout or an update. Once it is on a tag, CVS views the working copy as a static snapshot of a moment in history, and CVS won't let you change history, at least not easily. If you run cvs status or look at the CVS/Entries files, you'll see that there is a sticky tag set on each file. Here's the top level Entries file, for example:

         floss$ cat CVS/Entries
         D/a-subdir////
         D/b-subdir////
         D/c-subdir////
         /README.txt/1.1.1.1/Sun Apr 18 18:18:22 1999//TRelease-1999_05_01
         /hello.c/1.5/Tue Apr 20 07:24:10 1999//TRelease-1999_05_01
         floss$

Tags, like other sticky properties, are removed with the -A flag to update:

         floss$ cvs -q update -A
         M hello.c
         floss$

The modification to hello.c did not go away, however; CVS is still aware that the file changed with respect to the repository:

         floss$ cvs -q diff -c hello.c
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.5
         diff -c -r1.5 hello.c
         *** hello.c   1999/04/20 06:12:56     1.5
         --- hello.c   1999/05/04 20:09:17
         ***************
         *** 6,9 ****
         --- 6,10 --
             printf ("Hello, world!\n");
             printf ("between hello and goodbye\n");
             printf ("Goodbye, world!\n");
         +   /* a comment on the last line */
           }
         floss$

Now that you've reset with update, CVS will accept a commit:

         floss$ cvs ci -m "added comment to end of main function"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         cvs commit: Examining c-subdir
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <-  hello.c
         new revision: 1.6; previous revision: 1.5
         done
         floss$

The tag `Release-1999_05_01` is still attached to revision 1.5, of course. Compare the file's status before and after a reversion to the tag:

         floss$ cvs -q status hello.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:  1.6     Tue May  4 20:09:17 1999
            Repository revision:       1.6     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                (none)
            Sticky Date:               (none)
            Sticky Options:            (none)
         floss$ cvs -q update -r Release-1999_05_01
         U hello.c
         floss$ cvs -q status hello.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:  1.5     Tue May  4 20:21:12 1999
            Repository revision:       1.5     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                Release-1999_05_01 (revision: 1.5)
            Sticky Date:               (none)
            Sticky Options:            (none)
         floss$

Now, having just told you that CVS doesn't let you change history, I'll show you how to change history.

Node: Branches, Previous: Other Useful CVS Commands, Up: An Overview of CVS

### Branches

We've been viewing CVS as a kind of intelligent, coordinating library. However, it can also be thought of as a time machine (thanks to Jim Blandy for the analogy). So far, we've only seen how you can examine the past with CVS, without affecting anything. Like all good time machines, CVS also allows you to go back in time to change the past. What do you get then? Science fiction fans know the answer to that question: an alternate universe, running parallel to ours, but diverging from ours at exactly the point where the past was changed. A CVS branch splits a project's development into separate, parallel histories. Changes made on one branch do not affect the other.

Node: Branching Basics, Next: Merging Changes From Branch To Trunk, Up: Branches

### Branching Basics

Why are branches useful?

Let's return for a moment to the scenario of the developer who, in the midst of working on a new version of the program, receives a bug report about an older released version. Assuming the developer fixes the problem, she still needs a way to deliver the fix to the customer. It won't help to just find an old copy of the program somewhere, patch it up without CVS's knowledge, and ship it off. There would be no record of what was done; CVS would be unaware of the fix; and later if something was discovered to be wrong with the patch, no one would have a starting point for reproducing the problem.

It's even more ill-advised to fix the bug in the current, unstable version of the sources and ship that to the customer. Sure, the reported bug may be solved, but the rest of the code is in a half-implemented, untested state. It may run, but it's certainly not ready for prime time.

Because the last released version is thought to be stable, aside from this one bug, the ideal solution is to go back and correct the bug in the old release - that is, to create an alternate universe in which the last public release includes this bug fix.

That's where branches come in. The developer splits off a branch, rooted in the main line of development (the trunk) not at its most recent revisions, but back at the point of the last release. Then she checks out a working copy of this branch, makes whatever changes are necessary to fix the bug, and commits them on that branch, so there's a record of the bug fix. Now she can package up an interim release based on the branch and ship it to the customer.

Her change won't have affected the code on the trunk, nor would she want it to without first finding out whether the trunk needs the same bug fix or not. If it does, she can merge the branch changes into the trunk. In a merge, CVS calculates the changes made on the branch between the point where it diverged from the trunk and the branch's tip (its most recent state), then applies those differences to the project at the tip of the trunk. The difference between the branch's root and its tip works out, of course, to be precisely the bug fix.

Another good way to think of a merge is as a special case of updating. The difference is that in a merge, the changes to be incorporated are derived by comparing the branch's root and tip, instead of by comparing the working copy against the repository.

The act of updating is itself similar to receiving patches directly from their authors and applying them by hand. In fact, to do an update, CVS calculates the difference (that's "difference" as in the diff program) between the working copy and the repository and then applies that diff to the working copy just as the patch program would. This mirrors the way in which a developer takes changes from the outside world, by manually applying patch files sent in by contributors.

Thus, merging the bug fix branch into the trunk is just like accepting some outside contributor's patch to fix the bug. The contributor would have made the patch against the last released version, just as the branch's changes are against that version. If that area of code in the current sources hasn't changed much since the last release, the merge will succeed with no problems. If the code is now substantially different, however, the merge will fail with conflict (that is, the patch will be rejected), and some manual fiddling will be necessary. Usually this is accomplished by reading the conflicting area, making the necessary changes by hand, and committing. Figure 2.3 shows a picture of what happens in a branch and merge.

                      (branch on which bug was fixed)
                    .---------------->---------------.
                   /                                 |
                  /                                  |
                 /                                   |
                /                                    |
               /                                     V (<------ point of merge)
          ====*===================================================================>
                         (main line of development)

         [Figure 2.3: A branch and then a merge.  Time flows left to right.]

We'll now walk through the steps necessary to make this picture happen. Remember that it's not really time that's flowing from left to right in the diagram, but rather the revision history. The branch will not have been made at the time of the release, but is created later, rooted back at the release's revisions.

In our case, let's assume the files in the project have gone through many revisions since they were tagged as `Release-1999_05_01`, and perhaps files have been added as well. When the bug report regarding the old release comes in, the first thing we'll want to do is create a branch rooted at the old release, which we conveniently tagged `Release-1999_05_01`.

One way to do this is to first check out a working copy based on that tag, then create the branch by re-tagging with the -b (branch) option:

         floss$ cd ..
         floss$ ls
         myproj/
         floss$ cvs -q checkout -d myproj_old_release -r Release-1999_05_01 myproj
         U myproj_old_release/README.txt
         U myproj_old_release/hello.c
         U myproj_old_release/a-subdir/whatever.c
         U myproj_old_release/a-subdir/subsubdir/fish.c
         U myproj_old_release/b-subdir/random.c
         floss$ ls
         myproj/      myproj_old_release/
         floss$ cd myproj_old_release
         floss$ ls
         CVS/      README.txt  a-subdir/   b-subdir/   hello.c
         floss$ cvs -q tag -b Release-1999_05_01-bugfixes
         T README.txt
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         floss$

Take a good look at that last command. It may seem somewhat arbitrary that tag is used to create branches, but there's actually a reason for it: The tag name will serve as a label by which the branch can be retrieved later. Branch tags do not look any different from non-branch tags, and are subject to the same naming restrictions. Some people like to always include the word branch in the tag name itself (for example, `Release-1999_05_01-bugfix-branch`), so they can distinguish branch tags from other kinds of tags. You may want to do this if you find yourself often retrieving the wrong tag.

(And while we're at it, note the -d myproj_old_release option to checkout in the first CVS command. This tells checkout to put the working copy in a directory called myproj_old_release, so we won't confuse it with the current version in myproj. Be careful not to confuse this use of -d with the global option of the same name, or with the -d option to update.)

Of course, merely running the tag command does not switch this working copy over to the branch. Tagging never affects the working copy; it just records some extra information in the repository to allow you to retrieve that working copy's revisions later on (as a static piece of history or as a branch, as the case may be).

Retrieval can be done one of two ways (you're probably getting used to this motif by now!). You can check out a new working copy on the branch

         floss$ pwd
         /home/whatever
         floss$ cvs co -d myproj_branch -r Release-1999_05_01-bugfixes myproj

or switch an existing working copy over to it:

         floss$ pwd
         /home/whatever/myproj
         floss$ cvs update -r Release-1999_05_01-bugfixes

The end result is the same (well, the name of the new working copy's top-level directory may be different, but that's not important for CVS's purposes). If your current working copy has uncommitted changes, you'll probably want to use checkout instead of update to access the branch. Otherwise, CVS attempts to merge your changes into the working copy as it switches it over to the branch. In that case, you might get conflicts, and even if you didn't, you'd still have an impure branch. It won't truly reflect the state of the program as of the designated tag, because some files in the working copy will contain modifications made by you.

Anyway, let's assume that by one method or another you get a working copy on the desired branch:

         floss$ cvs -q status hello.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:  1.5     Tue Apr 20 06:12:56 1999
            Repository revision:       1.5     /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                Release-1999_05_01-bugfixes
         (branch: 1.5.2)
            Sticky Date:               (none)
            Sticky Options:            (none)
         floss$ cvs -q status b-subdir/random.c
         ===================================================================
         File: random.c                Status: Up-to-date
            Working revision:  1.2     Mon Apr 19 06:35:27 1999
            Repository revision:       1.2 /usr/local/cvs/myproj/b-subdir/random.c,v
            Sticky Tag:                Release-1999_05_01-bugfixes (branch: 1.2.2)
            Sticky Date:               (none)
            Sticky Options:            (none)
         floss$

(The contents of those `Sticky Tag` lines will be explained shortly.) If you modify hello.c and random.c, and commit

         floss$ cvs -q update
         M hello.c
         M b-subdir/random.c
         floss$ cvs ci -m "fixed old punctuation bugs"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <-  hello.c
         new revision: 1.5.2.1; previous revision: 1.5
         done
         Checking in b-subdir/random.c;
         /usr/local/cvs/myproj/b-subdir/random.c,v  <-  random.c
         new revision: 1.2.2.1; previous revision: 1.2
         done
         floss$

you'll notice that there's something funny going on with the revision numbers:

         floss$ cvs -q status hello.c b-subdir/random.c
         ===================================================================
         File: hello.c                 Status: Up-to-date
            Working revision:  1.5.2.1 Wed May  5 00:13:58 1999
            Repository revision:       1.5.2.1 /usr/local/cvs/myproj/hello.c,v
            Sticky Tag:                Release-1999_05_01-bugfixes (branch: 1.5.2)
            Sticky Date:               (none)
            Sticky Options:            (none)
         ===================================================================
         File: random.c                Status: Up-to-date
            Working revision:  1.2.2.1 Wed May  5 00:14:25 1999
            Repository revision:       1.2.2.1 /usr/local/cvs/myproj/b-subdir/random.c,v
            Sticky Tag:                Release-1999_05_01-bugfixes (branch: 1.2.2)
            Sticky Date:               (none)
            Sticky Options:            (none)
         floss$

They now have four digits instead of two!

A closer look reveals that each file's revision number is just the branch number (as shown on the `Sticky Tag` line) plus an extra digit on the end.

What you're seeing is a little bit of CVS's inner workings. Although you almost always use a branch to mark a project-wide divergence, CVS actually records the branch on a per-file basis. This project had five files in it at the point of the branch, so five individual branches were made, all with the same tag name: `Release-1999_05_01-bugfixes`.

Most people consider this per-file scheme a rather inelegant implementation on CVS's part. It's a bit of the old RCS legacy showing through-RCS didn't know how to group files into projects, and even though CVS does, it still uses code inherited from RCS to handle branches.

Ordinarily, you don't need to be too concerned with how CVS is keeping track of things internally, but in this case, it helps to understand the relationship between branch numbers and revision numbers. Let's look at the hello.c file; everything I'm about to say about hello.c applies to the other files in the branch (with revision/branch numbers adjusted accordingly).

The hello.c file was on revision 1.5 at the point where the branch was rooted. When we created the branch, a new number was tacked onto the end to make a branch number (CVS chooses the first unused even, nonzero integer). Thus, the branch number in this case became `1.5.2`. The branch number by itself is not a revision number, but it is the root (that is, the prefix) of all the revision numbers for hello.c along this branch.

However, when we ran that first CVS status in a branched working copy, hello.c's revision number showed up as only `1.5`, not `1.5.2.0` or something similar. This is because the initial revision on a branch is always the same as the trunk revision of the file, where the branch sprouts off. Therefore, CVS shows the trunk revision number in status output, for as long as the file is the same on both branch and trunk.

Once we had committed a new revision, hello.c was no longer the same on both trunk and branch - the branch incarnation of the file had changed, while the trunk remained the same. Accordingly, hello.c was assigned its first branch revision number. We saw this in the status output after the commit, where its revision number is clearly `1.5.2.1`.

The same story applies to the random.c file. Its revision number at the time of branching was `1.2`, so its first branch is `1.2.2`, and the first new commit of random.c on that branch received the revision number `1.2.2.1`.

There is no numeric relationship between `1.5.2.1` and `1.2.2.1` - no reason to think that they are part of the same branch event, except that both files are tagged with `Release-1999_05_01-bugfixes`, and the tag is attached to branch numbers `1.5.2` and `1.2.2` in the respective files. Therefore, the tag name is your only handle on the branch as a project-wide entity. Although it is perfectly possible to move a file to a branch by using the revision number directly

         floss$ cvs update -r 1.5.2.1 hello.c
         U hello.c
         floss$

it is almost always ill-advised. You would be mixing the branch revision of one file with non-branch revisions of the others. Who knows what losses may result? It is better to use the branch tag to refer to the branch and do all files at once by not specifying any particular file. That way you don't have to know or care what the actual branch revision number is for any particular file.

It is also possible to have branches that sprout off other branches, to any level of absurdity. For example, if a file has a revision number of `1.5.4.37.2.3`, its revision history can be diagrammed like this:

                           1.1
                            |
                           1.2
                            |
                           1.3
                            |
                           1.4
                            |
                           1.5
                          /   \
                         /     \
                        /       \
                    (1.5.2)   (1.5.4)         <--- (these are branch numbers)
                      /           \
                  1.5.2.1        1.5.4.1
                     |              |
                  1.5.2.2        1.5.4.2
                     |              |
                   (etc)          (...)       <--- (collapsed 34 revisions for brevity)
                                    |
                                 1.5.4.37
                                   /
                                  /
                            (1.5.4.37.2)      <--- (this is also a branch number)
                                /
                               /
                        1.5.4.37.2.1
                              |
                        1.5.4.37.2.2
                              |
                        1.5.4.37.2.3

         [Figure 2.4: An unusually high degree of branching.  Time flows downward.]

Admittedly, only the rarest circumstances make such a branching depth necessary, but isn't it nice to know that CVS will go as far as you're willing to take it? Nested branches are created the same way as any other branch: Check out a working copy on branch `N`, run cvs tag -b branchname in it, and you'll create branch `N.M` in the repository (where `N` represents the appropriate branch revision number in each file, such as `1.5.2.1`, and `M` represents the next available branch at the end of that number, such as `2`).

Node: Merging Changes From Branch To Trunk, Next: Multiple Merges, Previous: Branching Basics, Up: Branches

### Merging Changes From Branch To Trunk

Now that the bug fix has been committed on the branch, let's switch the working copy over to the highest trunk revisions and see if the bug fix needs to be done there, too. We'll move the working copy off the branch by using update -A (branch tags are like other sticky properties in this respect) and then diffing against the branch we just left:

         floss$ cvs -q update -d -A
         U hello.c
         U b-subdir/random.c
         floss$ cvs -q diff -c -r Release-1999_05_01-bugfixes
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.5.2.1
         retrieving revision 1.6
         diff -c -r1.5.2.1 -r1.6
         *** hello.c   1999/05/05 00:15:07     1.5.2.1
         --- hello.c   1999/05/04 20:19:16     1.6
         ***************
         *** 4,9 ****
           main ()
           {
             printf ("Hello, world!\n");
         !   printf ("between hello and good-bye\n");
             printf ("Goodbye, world!\n");
           }
         --- 4,10 --
           main ()
           {
             printf ("Hello, world!\n");
         !   printf ("between hello and goodbye\n");
             printf ("Goodbye, world!\n");
         +   /* a comment on the last line */
           }
         Index: b-subdir/random.c
         ===================================================================
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.2.2.1
         retrieving revision 1.2
         diff -c -r1.2.2.1 -r1.2
         *** b-subdir/random.c 1999/05/05 00:15:07     1.2.2.1
         --- b-subdir/random.c 1999/04/19 06:35:27     1.2
         ***************
         *** 4,8 ****
           void main ()
           {
         !   printf ("A random number.\n");
           }
         --- 4,8 --
           void main ()
           {
         !   printf ("a random number\n");
           }
         floss$

The diff shows that good-bye is spelled with a hyphen in the branch revision of hello.c, and that the trunk revision of that file has a comment near the end that the branch revision doesn't have. Meanwhile, in random.c, the branch revision has a capital "A" and a period, whereas the trunk doesn't.

To actually merge the branch changes into the current working copy, run update with the -j flag (the same j for "join" that we used to revert a file to an old revision before):

         floss$ cvs -q update -d -j Release-1999_05_01-bugfixes
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.5
         retrieving revision 1.5.2.1
         Merging differences between 1.5 and 1.5.2.1 into hello.c
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.2
         retrieving revision 1.2.2.1
         Merging differences between 1.2 and 1.2.2.1 into random.c
         floss$ cvs -q update
         M hello.c
         M b-subdir/random.c
         floss$ cvs -q ci -m "merged from branch Release-1999_05_01-bugfixes"
         Checking in hello.c;
         /usr/local/cvs/myproj/hello.c,v  <-  hello.c
         new revision: 1.7; previous revision: 1.6
         done
         Checking in b-subdir/random.c;
         /usr/local/cvs/myproj/b-subdir/random.c,v  <-  random.c
         new revision: 1.3; previous revision: 1.2
         done
         floss$

This takes the changes from the branch's root to its tip and merges them into the current working copy (which subsequently shows those modifications just as though the files had been hand-edited into that state). The changes are then committed onto the trunk, since nothing in the repository changed when a working copy underwent a merge.

Although no conflicts were encountered in this example, it's quite possible (even probable) that there would be some in a normal merge. If that happens, they need to be resolved like any other conflict, and then committed.

Node: Multiple Merges, Next: Creating A Tag Or Branch Without A Working Copy, Previous: Merging Changes From Branch To Trunk, Up: Branches

### Multiple Merges

Sometimes a branch will continue to be actively developed even after the trunk has undergone a merge from it. For example, this can happen if a second bug in the previous public release is discovered and has to be fixed on the branch. Maybe someone didn't get the joke in random.c, so on the branch, you have to add a line explaining it

         floss$ pwd
         /home/whatever/myproj_branch
         floss$ cat b-subdir/random.c
         /* Print out a random number. */
         #include <stdio.h>
         void main ()
         {
           printf ("A random number.\n");
           printf ("Get the joke?\n");
         }
         floss$

and commit. If that bug fix also needs to be merged into the trunk, you might be tempted to try the same update command as before in the trunk working copy to "re-merge":

         floss$ cvs -q update -d -j Release-1999_05_01-bugfixes
         RCS file: /usr/local/cvs/myproj/hello.c,v
         retrieving revision 1.5
         retrieving revision 1.5.2.1
         Merging differences between 1.5 and 1.5.2.1 into hello.c
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.2
         retrieving revision 1.2.2.2
         Merging differences between 1.2 and 1.2.2.2 into random.c
         rcsmerge: warning: conflicts during merge
         floss$

As you can see, that didn't have quite the desired effect-we got a conflict, even though the trunk copy hadn't been modified there and, therefore, no conflict was expected.

The trouble was that the update command behaved exactly as described: It tried to take all the changes between the branch's root and tip and merge them into the current working copy. The only problem is, some of those changes had already been merged into this working copy. That's why we got the conflict:

         floss$ pwd
         /home/whatever/myproj
         floss$ cat b-subdir/random.c
         /* Print out a random number. */
         #include <stdio.h
         void main ()
         {
         <<<<<<< random.c
           printf ("A random number.\n");
         =======
           printf ("A random number.\n");
           printf ("Get the joke?\n");
         >>>>>>> 1.2.2.2
         }
         floss$

You could go through resolving all such conflicts by hand-it's usually not hard to tell what you need to do in each file. Nevertheless, it is even better to avoid a conflict in the first place. By passing two -j flags instead of one, you'll get only those changes from where you last merged to the tip instead of all of the changes on the branch, from root to tip. The first -j gives the starting point on the branch, and the second is just the plain branch name (which implies the tip of the branch).

The question then is, how can you specify the point on the branch from which you last merged? One way is to qualify by using a date along with the branch tag name. CVS provides a special syntax for this:

         floss$ cvs -q update -d -j "Release-1999_05_01-bugfixes:2 days ago" \
                              -j Release-1999_05_01-bugfixes
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.2.2.1
         retrieving revision 1.2.2.2
         Merging differences between 1.2.2.1 and 1.2.2.2 into random.c
         floss$

If the branch tag name is followed by a colon and then a date (in any of the usual CVS date syntaxes), CVS will include only changes later than that date. So if you knew that the original bug fix was committed on the branch three days ago, the preceding command would merge the second bug fix only.

A better way, if you plan ahead, is to tag the branch after each bug fix (just a regular tag - we're not starting a new branch here or anything like that). Suppose after fixing the bug in the branch and committing, you do this in the branch's working copy:

         floss$ cvs -q tag Release-1999_05_01-bugfixes-fix-number-1
         T README.txt
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         floss$

Then, when it's time to merge the second change into the trunk, you can use that conveniently placed tag to delimit the earlier revision:

         floss$ cvs -q update -d -j Release-1999_05_01-bugfixes-fix-number-1 \
                              -j Release-1999_05_01-bugfixes
         RCS file: /usr/local/cvs/myproj/b-subdir/random.c,v
         retrieving revision 1.2.2.1
         retrieving revision 1.2.2.2
         Merging differences between 1.2.2.1 and 1.2.2.2 into random.c
         floss$

This way, of course, is much better than trying to recall how long ago you made one change versus another, but it only works if you remember to tag the branch every time it is merged to the trunk. The lesson, therefore, is to tag early and tag often! It's better to err on the side of too many tags (as long as they all have descriptive names) than to have too few. In these last examples, for instance, there was no requirement that the new tag on the branch have a name similar to the branch tag itself. Although I named it `Release-1999_05_01-bugfixes-fix-number-1`, it could just as easily have been `fix1`. However, the former is preferable, because it contains the name of the branch and thus won't ever be confused with a tag on some other branch. (Remember that tag names are unique within files, not within branches. You can't have two tags named `fix1` in the same file, even if they refer to revisions on different branches.)

Node: Creating A Tag Or Branch Without A Working Copy, Previous: Multiple Merges, Up: Branches

### Creating A Tag Or Branch Without A Working Copy

As stated earlier, tagging affects the repository, not the working copy. That begs the question: Why require a working copy at all when tagging? The only purpose that it serves is to designate which project and which revisions of the various files in the project are being tagged. If you could specify the project and revisions independently of the working copy, no working copy would be necessary.

There is such a way: the rtag command (for "repository tag"). It's very similar to tag; a couple of examples will explain its usage. Let's go back to the moment when the first bug report came in and we needed to create a branch rooted at the last public release. We checked out a working copy at the release tag and then ran `tag -b` on it:

         floss$ cvs tag -b Release-1999_05_01-bugfixes

This created a branch rooted at `Release-1999_05_01`. However, because we know the release tag, we could have used it in an rtag command to specify where to root the branch, not even bothering with a working copy:

         floss$ cvs rtag -b -r Release-1999_05_01 Release-1999_05_01-bugfixes myproj

That's all there is to it. That command can be issued from anywhere, inside or outside a working copy. However, your CVSROOT environment variable would have to point to the repository, of course, or you can specify it with the global -d option. It works for non-branch tagging, too, but it's less useful that way because you have to specify each file's revision number, one by one. (Or you can refer to it by tag, but then you'd obviously already have a tag there, so why would you want to set a second one on the exact same revisions?)

You now know enough to get around in CVS and probably enough to start working with other people on a project. There are still a few minor features that haven't been introduced, as well as some unmentioned but useful options to features already seen. These will all be presented as appropriate in chapters to come, in scenarios that will demonstrate both how and why to use them. When in doubt, don't hesitate to consult the Cederqvist manual; it is an indispensable resource for serious CVS users.

Node: Repository Administration, Next: Advanced CVS, Previous: An Overview of CVS, Up: Top

## Repository Administration

In An Overview of CVS, you learned enough CVS to use it effectively as a project participant. If you're going to be a project maintainer, however, you'll need to know how to install CVS and administer repositories. In this chapter, we'll throw back the curtain and look in detail at how the repository is structured, and how CVS uses it. You'll learn all the major steps CVS goes through during updates and commits, and how you can modify its behavior. By understanding how CVS works, you'll also be able to trace problems to their causes, and fix them in maintainable ways.

This may sound very involved, but remember that CVS has already proven quite long-lived, and will probably be around for many years to come. Whatever you learn now will be useful for a long time. CVS also tends to become more indispensable the more you use it. If you're going to be that dependent on something (and trust me, you are), it's worth really getting to know it.

With that in mind, let's begin at the beginning: putting CVS on your system.

Node: Getting And Installing CVS, Next: Anatomy Of A CVS Distribution, Up: Repository Administration

### Getting And Installing CVS

In many cases, you won't have to go out and get CVS, because it will already be on your system. If you run one of the major Linux or FreeBSD distributions, it's probably already installed in /usr/bin or some other likely location. If not, Red Hat Linux users can usually find an RPM (Red Hat Package) for the latest, or nearly latest, version of CVS in their distributions. And Debian users can install the latest Debian package with these commands:

         floss$ apt-get update
         floss$ apt-get install cvs

If CVS isn't already on your machine, you'll probably have to build it from source. If you're a non-Unix user, you'll probably find it easier to get a prebuilt binary for your operating system (more on that later). Fortunately, CVS is fully autoconfiscated - that is, it uses the GNU autoconfiguration mechanism, making compilation from source surprisingly easy.

Node: Getting And Building CVS Under Unix, Next: Getting And Installing CVS Under Windows, Up: Getting And Installing CVS

### Getting And Building CVS Under Unix

As of this writing, there are two canonical sites from which you can download CVS. One is the Free Software Foundation's FTP site, ftp://ftp.gnu.org/gnu/cvs/, which offers CVS as an official GNU tool. The other is Cyclic Software's download site. Cyclic Software is, if not the maintainer of CVS, then the "maintainer of the maintainers", by providing a repository server and download access for users and developers. They distribute releases from http://download.cyclic.com/pub/.

Either location is fine. In the following example, I use Cyclic Software's site. If you point your FTP client (probably your Web browser) there, you'll see a list of directories, something like this:

         Index of /pub
             cvs-1.10.5/            18-Feb-99 21:36      -
             cvs-1.10.6/            17-May-99 10:34      -
             cvs-1.10/              09-Dec-98 17:26      -
             macintosh/             23-Feb-99 00:53      -
             os2/                   09-Dec-98 17:26      -
             packages/              09-Dec-98 17:26      -
             rcs/                   09-Dec-98 17:26      -
             tkcvs/                 09-Dec-98 17:26      -
             training/              09-Dec-98 17:26      -
             unix/                  09-Dec-98 17:26      -
             vms/                   09-Dec-98 17:26      -

Pay attention to the directories beginning with "cvs-" (you can ignore most of the others). There are three such directories, which means that you're already faced with a choice: Get the designated "stable" release, or go with a newer (but less-tested) interim release. The stable releases have only one decimal point, as in "cvs-1.10", whereas the interim releases have minor version increments tacked on the end, as in "1.10.5".

The GNU site usually only offers the major releases, not the interim ones, so you won't see all of this if you get CVS from there. In general, the interim releases have been pretty safe, and sometimes contain fixes to bugs that were found in the major release. Your best policy is to go with the highest interim release, but if you encounter any problems with it, be prepared to drop back to the previous release, as many times as necessary. The highest release listed in the earlier example is cvs-1.10.6. Entering that directory, we see this:

         Index of /pub/cvs-1.10.6
             cvs-1.10.6.tar.gz      17-May-99 08:44   2.2M

That's it - the full source code to CVS. Just download it to your machine, and you're ready to build. At this point, if you're already familiar with the standard build process for GNU tools, you know what to do and probably don't need to read anything between here and the section Anatomy Of A CVS Distribution. On the other hand, if you're not sure how to proceed, then read on....

The following compilation instructions and examples assume that you have a fairly standard distribution of Unix. Any of the free versions of Unix (for example, FreeBSD or Linux) should work with no problem, as should the major commercial Unix versions (such as SunOS/Solaris, AIX, HP-UX, or Ultrix). Even if these instructions don't work for you exactly as written, don't give up hope. Although covering the details of compiling on every operating system is beyond the scope of this book, I'll give some pointers to other help resources later in this chapter.

Anyway, to proceed with the compilation, first unpack the tar file using GNU gunzip and tar (if you don't have these installed on your system, you can get gunzip from ftp://ftp.gnu.org/gnu/gzip/ and GNU's version of tar from ftp://ftp.gnu.org/gnu/tar/):

         floss$ gunzip cvs-1.10.6.tar.gz
         floss$ tar xvf cvs-1.10.6.tar

You'll see a lot of file names fly by on your screen.

Now you have a new directory on your machine - cvs-1.10.6 - and it is populated with the CVS source code. Go into that directory and configure CVS for your system, by using the provided configure script:

         floss$ cd cvs-1.10.6
         floss$  ./configure
         creating cache ./config.cache
         checking for gcc... gcc
         checking whether we are using GNU C... yes
         checking whether gcc accepts -g... yes
         checking how to run the C preprocessor... gcc -E
           (etc)

When the configure command finishes, the source tree will know everything it needs to know about compiling on your machine. The next step is to type:

         floss$ make

You'll see lots of output fly by, then type:

         floss$ make install

You'll see yet more output fly by; when it's all over, CVS will be installed on your system. (You will probably need to do that last step as the superuser.)

By default, the CVS executable will end up as `/usr/local/bin/cvs`. This assumes you have a decent make program installed on your system (again, if you don't have one, get the GNU project's make from ftp://ftp.gnu.org/gnu/make/).

If you want CVS to install to a location other than /usr/local/bin, you should change how you run the initial configuration step. For example,

         floss$ ./configure --prefix=/usr

results in CVS being installed as /usr/bin/cvs (it always ends up as PREFIX/bin/cvs). The default prefix is /usr/local, which is fine for most installations.

Note To Experienced Users: Although older versions of CVS consisted of more than just an executable in that they depended on having RCS installed as well, this has not been the case since Version 1.10. Therefore, you don't need to worry about any libraries or executables other than cvs itself.

If you just intend to use CVS to access remote repositories, the preceding is all you need to do. If you also plan to serve a repository from this system, a few additional steps are necessary, which are covered later in this chapter.

Node: Getting And Installing CVS Under Windows, Next: Getting And Installing CVS On A Macintosh, Previous: Getting And Building CVS Under Unix, Up: Getting And Installing CVS

### Getting And Installing CVS Under Windows

Unless you're truly religious about having the source code to your executable, you don't need to compile CVS from source on your Windows box. Unlike Unix, the necessary compilation tools probably do not already exist on your system, so a source build would involve first going out and getting those tools. Because such a project is beyond the scope of this book, I'll just give instructions for getting a precompiled CVS binary.

First, note that Windows binary distributions of CVS are usually made only for major releases of CVS - not for the interim releases - and are not found on the GNU FTP site. So you'll need to go to Cyclic Software's download site, where in the major version directory, http://download.cyclic.com/pub/cvs-1.10/, you'll see an extra subdirectory

         Index of /pub/cvs-1.10
             cvs-1.10.tar.gz        14-Aug-98 09:35   2.4M
             windows/

inside of which is a ZIP file:

         Index of /pub/cvs-1.10/windows
             cvs-1.10-win.zip       14-Aug-98 10:10   589k

This ZIP file contains a binary distribution of CVS. Download and extract that ZIP file:

         floss$ unzip cvs-1.10-win.zip

         Archive:  cvs-1.10-win.zip
           inflating: cvs.html
           inflating: cvs.exe
           inflating: README
           inflating: FAQ
           inflating: NEWS
           inflating: patch.exe
           inflating: win32gnu.dll

The README there contains detailed instructions. For most installations, they can be summarized as follows: Put all of the EXE and DLL files in a directory in your PATH. Additionally, if you're going to be using the pserver method to access a remote repository, you may need to put the following in your `C:\AUTOEXEC.BAT` file and reboot:

         set HOME=C:

This tells CVS where to store the .cvspass file.

CVS running under Windows cannot currently serve repositories to remote machines; it can be a client (connecting to remote repositories), and operate in local mode (using a repository on the same machine). For the most part, this book assumes that CVS under Windows is operating as a client. However, it shouldn't be too hard to set up a local repository under Windows after reading the Unix-oriented instructions in the rest of this chapter.

If you are only accessing remote repositories, you may not even need to run CVS. There is a tool called WinCvs that implements only the client-side portion of CVS. It is distributed separately from CVS itself but, like CVS, is freely available under the GNU General Public License. More information is available from http://www.wincvs.org.

Node: Getting And Installing CVS On A Macintosh, Next: Limitations Of The Windows And Macintosh Versions, Previous: Getting And Installing CVS Under Windows, Up: Getting And Installing CVS

### Getting And Installing CVS On A Macintosh

CVS is available for the Macintosh, but not as part of the main distribution. At the moment, there are actually three separate Macintosh CVS clients available:

- MacCvs - http://www.wincvs.org
- MacCVSClient - http://www.glink.net.hk/~jb/MacCVSClient or http://www.cyclic.com/maccvsclient/
- MacCVS Pro - http://www.maccvs.org

Frankly, I have no idea which one is best. Try them all, not necessarily in the order given, and see which one you like. MacCVS Pro seems to be under active development. MacCvs is apparently a companion project of WinCVS and shares a home page with it. (As of this writing, a notice on the WinCVS page states, "Development of MacCvs will be resumed soon.", whatever that means.)

Node: Limitations Of The Windows And Macintosh Versions, Previous: Getting And Installing CVS On A Macintosh, Up: Getting And Installing CVS

### Limitations Of The Windows And Macintosh Versions

The Windows and Macintosh distributions of CVS are generally limited in functionality. They can all act as clients, meaning that they can contact a repository server to obtain a working copy, commit, update, and so on. But they can't serve repositories themselves. If you set it up right, the Windows port can use a local-disk repository, but it still can't serve projects from that repository to other machines. In general, if you want to have a network-accessible CVS repository, you must run the CVS server on a Unix box.

Node: Anatomy Of A CVS Distribution, Next: Starting A Repository, Previous: Getting And Installing CVS, Up: Repository Administration

### Anatomy Of A CVS Distribution

The preceding instructions are designed to get you up and running quickly, but there's a lot more inside a CVS source distribution than just the code. Here's a quick road map to the source tree, so you'll know which parts are useful resources and which can be ignored.

Node: Informational Files, Next: Subdirectories, Up: Anatomy Of A CVS Distribution

### Informational Files

In the top level of the distribution tree, you'll find several files containing useful information (and pointers to further information). They are, in approximate order of importance:

- `NEWS` - This file lists the changes from one release to the next, in reverse chronological order (that is, most recent first). If you've already been using CVS for a while and have just upgraded to a new version, you should look at the NEWS file to see what new features are available. Also, although most changes to CVS preserve backward compatibility, noncompatible changes do occur from time to time. It's better to read about them here than be surprised when CVS doesn't behave the way you expect it to.
- `BUGS` - This file contains exactly what you think it does: a list of known bugs in CVS. They usually aren't show-stoppers, but you should read over them whenever you install a new release.
- `DEVEL-CVS` - This file is the CVS "constitution". It describes the process by which changes are accepted into the main CVS distribution and the procedures through which a person becomes a CVS developer. You don't really need to read it if you just want to use CVS; however, it's highly interesting if you want to understand how the mostly uncoordinated efforts of people scattered across the globe coalesce into a working, usable piece of software. And of course, it's required reading if you plan to submit a patch (be it a bug fix or new feature) to CVS.
- `HACKING` - Despite its name, the HACKING file doesn't say much about the design or implementation of CVS. It's mainly a guide to coding standards and other technical administrivia for people thinking of writing a patch to CVS. It can be thought of as an addendum to the DEVEL-CVS file. After you understand the basic philosophy of CVS development, you must read the HACKING file to translate that into concrete coding practices.
- `FAQ` - This is the CVS "Frequently Asked Questions" document. Unfortunately it has a rather spotty maintenance history. David Grubbs took care of it until 1995, then he (presumably) got too busy and it languished for a while. Eventually, in 1997, Pascal Molli took over maintenance. Molli also didn't have time to maintain it by hand, but at least he found time to put it into his automated FAQ-O-Matic system, which allows the public to maintain the FAQ in a decentralized manner (basically, anyone can edit or add entries via a Web form). This was probably a good thing, in that at least the FAQ was once again being maintained; however, its overall organization and quality control are not on the same level as if a person were maintaining it.

  The master version of the FAQ is always available from Molli's Web site (http://www.loria.fr/~molli/cvs-index.html, under the link "Documentation"). The FAQ file shipped with CVS distributions is generated automatically from that FAQ-O-Matic database, so by the time it reaches the public it's already a little bit out of date. Nevertheless, it can be quite helpful when you're looking for hints and examples about how to do something specific (say, merging a large branch back into the trunk or resurrecting a removed file). The best way to use it is as a reference document; you can bring it up in your favorite editor and do text searches on terms that interest you. Trying to use it as a tutorial would be a mistake - it's missing too many important facts about CVS to serve as a complete guide.

Node: Subdirectories, Next: The Cederqvist Manual, Previous: Informational Files, Up: Anatomy Of A CVS Distribution

### Subdirectories

The CVS distribution contains a number of subdirectories. In the course of a normal installation, you won't have to navigate among them, but if you want to go poking around in the sources, it's nice to know what each one does. Here they are:

         contrib/
         diff/
         doc/
         emx/
         lib/
         man/
         os2/
         src/
         tools/
         vms/
         windows-NT/
         zlib/

The majority of these can be ignored. The emx/, os2/, vms/, and windows-NT/ subdirectories all contain operating-system-specific source code, which you would only need if you're actually trying to debug a code-level problem in CVS (an unlikely situation, though not unheard of). The diff/ and zlib/ subdirectories contain CVS's internal implementations of the diff program and the GNU gzip compression library, respectively. (CVS uses the latter to reduce the number of bits it has to send over the network when accessing remote repositories.)

The contrib/ and tools/ subdirectories contain free third-party software meant to be used with CVS. In contrib/, you will find an assortment of small, specialized shell scripts (read contrib/README to find out what they do). The tools/ subdirectory used to contain contributed software, but now contains a README file, which says in part:

         This subdirectory formerly contained tools that can be used with CVS.
         In particular, it used to contain a copy of pcl-cvs version 1.x.
         Pcl-cvs is an Emacs interface to CVS.

         If you are looking for pcl-cvs, we'd suggest pcl-cvs version 2.x, at:
             ftp://ftp.weird.com/pub/local/

The PCL-CVS package it's referring to is very handy, and I'll have more to say about it in Third-Party Tools.

The src/ and lib/ subdirectories contain the bulk of the CVS source code, which involves the CVS internals. The main data structures and commands are implemented in src/, whereas lib/ contains small code modules of general utility that CVS uses.

The man/ subdirectory contains the CVS man pages (intended for the Unix online manual system). When you ran make install, they were incorporated into your Unix system's regular man pages, so you can type

         floss$ man cvs

and get a rather terse introduction and subcommand reference to CVS. Although useful as a quick reference, the man pages may not be as up to date or complete as the Cederqvist manual (see the next section); however, the man pages are more likely to be incomplete than actually wrong, if it's any comfort.

Node: The Cederqvist Manual, Next: Other Sources Of Information, Previous: Subdirectories, Up: Anatomy Of A CVS Distribution

### The Cederqvist Manual

That leaves the doc/ subdirectory, whose most important inhabitant is the famed Cederqvist. These days, it's probably a stretch to call it "the Cederqvist". Although Per Cederqvist (of Signum Support, Linkoping Sweden, www.signum.se) wrote the first version around 1992, it has been updated since then by many other people. For example, when contributors add a new feature to CVS, they usually also document it in the Cederqvist.

The Cederqvist manual is written in Texinfo format, which is used by the GNU project because it's relatively easy to produce both online and printed output from it (in Info and PostScript formats, respectively). The Texinfo master file is doc/cvs.texinfo, but CVS distributions come with the Info and PostScript pregenerated, so you don't have to worry about running any Texinfo tools yourself.

Although the Cederqvist can be used as an introduction and tutorial, it is probably most useful as a reference document. For that reason, most people browse it online instead of printing it out (although the PostScript file is `doc/cvs.ps`, for those with paper to spare). If this is the first time you've installed CVS on your system, you'll have to take an extra step to make sure the manual is accessible online.

The Info files (doc/cvs.info, doc/cvs.info-1, doc/cvs.info-2, and so on) were installed for you when you ran make install. Although the files were copied into the system's Info tree, you may still have to add a line for CVS to the Info table of contents, the "Top" node. (This will only be necessary if this is the first time CVS has been installed on your system; otherwise, the entry from previous installations should already be in the table of contents.)

If you've added new Info documentation before, you may be familiar with the process. First figure out where the Info pages were installed. If you used the default installation (in /usr/local/), then the Info files are /usr/local/info/cvs.info*. If you installed using

         floss$ ./configure --prefix=/usr

the files ended up as /usr/info/cvs.*. After you locate the files, you'll need to add a line for CVS to the Info table of contents, which is in a file named dir in that directory (so in the latter case, it would be /usr/info/dir). If you don't have root access, ask your system administrator to do it. Here is an excerpt from dir before the reference to CVS documentation was added:

         * Bison: (bison).         The Bison parser generator.
         * Cpp: (cpp).             The GNU C preprocessor.
         * Flex: (flex).           A fast scanner generator

And here is the same region of dir afterwards:

         * Bison: (bison).         The Bison parser generator.
         * Cpp: (cpp).             The GNU C preprocessor.
         * Cvs: (cvs).             Concurrent Versions System
         * Flex: (flex).           A fast scanner generator

The format of the line is very important. You must include the asterisk, spaces, and colon in `* Cvs:` and the parentheses and period in `(cvs).` after it. If any of these elements are missing, the Info dir format will be corrupt, and you'll be unable to read the Cederqvist.

Once the manual is installed and referred to from the table of contents, you can read it with any Info-compatible browser. The ones most likely to be installed on a typical Unix system are either the command-line Info reader, which can be invoked this way if you want to go straight to the CVS pages

         floss$ info cvs

and the one within Emacs, which is invoked by typing

         M-x info

or

         C-h i

Take whatever time is necessary to get the Cederqvist set up properly on your system when you install CVS; it will pay off many times down the road when you need to look something up.

Node: Other Sources Of Information, Previous: The Cederqvist Manual, Up: Anatomy Of A CVS Distribution

### Other Sources Of Information

In addition to the Cederqvist, the FAQ, and the other files in the distribution itself, there are Internet resources devoted to CVS. If you're going to administrate a CVS server, you'll probably want to join the info-cvs mailing list. To subscribe, send email to info-cvs-request@gnu.org (the list itself is info-cvs@gnu.org). Traffic can be medium to heavy, around 10 to 20 emails a day, most of them questions seeking answers. The majority of these can be deleted without reading (unless you want to help people by answering their questions, which is always nice), but every now and then someone will announce the discovery of a bug or announce a patch that implements some feature you've been wanting.

You can also join the formal bug report mailing list, which includes every bug report sent in. This probably isn't necessary, unless you intend to help fix the bugs, which would be great, or you're terrifically paranoid and want to know about every problem other people find with CVS. If you do want to join, send email to bug-cvs-request@gnu.org.

There's also a Usenet newsgroup, `comp.software.config-mgmt`, which is about version control and configuration management systems in general, in which there is a fair amount of discussion about CVS.

Finally, there are at least three Web sites devoted to CVS. Cyclic Software's http://www.cyclic.com has been CVS's informal home site for a few years, and probably will continue to be for the foreseeable future. Cyclic Software also provides server space and Net access for the repository where the CVS sources are kept. The Cyclic Web pages contain comprehensive links to experimental patches for CVS, third-party tools that work with CVS, documentation, mailing list archives, and just about everything else. If you can't find what you need in the distribution, http://www.cyclic.com is the place to start looking.

Two other good sites are Pascal Molli's http://www.loria.fr/~molli/cvs-index.html and Sean Dreilinger's http://durak.org/cvswebsites/. The biggest attraction at Molli's site is, of course, the FAQ, but it also has links to CVS-related tools and mailing list archives. Dreilinger's site specializes in information about using CVS to manage Web documents and also has a CVS-specific search engine.

Node: Starting A Repository, Next: The Password-Authenticating Server, Previous: Anatomy Of A CVS Distribution, Up: Repository Administration

### Starting A Repository

Once the CVS executable is installed on your system, you can start using it right away as a client to access remote repositories, following the procedures described in An Overview of CVS. However, if you want to serve revisions from your machine, you have to create a repository there. The command to do that is

         floss$ cvs -d /usr/local/newrepos init

where `/usr/local/newrepos` is a path to wherever you want the repository to be (of course, you must have write permission to that location, which may imply running the command as the root user). It may seem somewhat counterintuitive that the location of the new repository is specified before the init subcommand instead of after it, but by using the -d option, it stays consistent with other CVS commands.

The command will return silently after it is run. Let's examine the new directory:

         floss$ ls -ld /usr/local/newrepos
         drwxrwxr-x   3 root     root         1024 Jun 19 17:59 /usr/local/newrepos/
         floss$ cd /usr/local/newrepos
         floss$ ls
         CVSROOT
         floss$ cd CVSROOT
         floss$ ls
         checkoutlist     config,v        history     notify     taginfo,v
         checkoutlist,v   cvswrappers     loginfo     notify,v   verifymsg
         commitinfo       cvswrappers,v   loginfo,v   rcsinfo    verifymsg,v
         commitinfo,v     editinfo        modules     rcsinfo,v
         config           editinfo,v      modules,v   taginfo

         floss$

The single subdirectory in the new repository - CVSROOT/ - contains various administrative files that control CVS's behavior. Later on, we'll examine those files one by one; for now, the goal is just to get the repository working. In this case, "working" means users can import, check out, update, and commit projects.

Don't confuse the CVSROOT environment variable introduced in An Overview of CVS with this CVSROOT subdirectory in the repository. They are unrelated - it is an unfortunate coincidence that they share the same name. The former is a way for users to avoid having to type `-d <repository-location>` every time they use CVS; the latter is the administrative subdirectory of a repository.

Once the repository is created, you must take care of its permissions. CVS does not require any particular, standardized permission or file ownership scheme; it merely needs write access to the repository. However - partly for security reasons, but mainly for your own sanity as an administrator - I highly recommend that you take the following steps:

1. Add a Unix group `cvs` to your system. Any users who need to access the repository should be in this group. For example, here's the relevant line from my machine's `/etc/group` file:

                 cvs:*:105:kfogel,sussman,jimb,noel,lefty,fitz,craig,anonymous,jrandom

2. Make the repository's group ownership and permissions reflect this new group:

                 floss$ cd /usr/local/newrepos
                 floss$ chgrp -R cvs .
                 floss$ chmod ug+rwx . CVSROOT

Now any of the users listed in that group can start a project by running `cvs import`, as described in An Overview of CVS. Checkout, update, and commit should work as well. They can also reach the repository from remote locations by using the `:ext:` method, assuming that they have rsh or ssh access to the repository machine. (You may have noticed that the chgrp and chmod commands in that example gave write access to a user named `anonymous`, which is not what one would expect. The reason is that even anonymous, read-only repository users need system-level write access, so that their CVS processes can create temporary lockfiles inside the repository. CVS enforces the "read-only" restriction of anonymous access not through Unix file permissions, but by other means, which will be covered in Anonymous Access.)

If your repository is intended to serve projects to the general public, where contributors won't necessarily have accounts on the repository machine, you should set up the password-authenticating server now (see The Password-Authenticating Server). It's necessary for anonymous read-only access, and it's also probably the easiest way to grant commit access to certain people without giving them full accounts on the machine.

Node: The Password-Authenticating Server, Next: Anonymous Access, Previous: Starting A Repository, Up: Repository Administration

### The Password-Authenticating Server

Before running through the steps needed to set up the password server, let's examine how such connections work in the abstract. When a remote CVS client uses the `:pserver:` method to connect to a repository, the client is actually contacting a specific port number on the server machine - specifically, port number 2401 (which is 49 squared, if you like that sort of thing). Port 2401 is the designated default port for the CVS pserver, although one could arrange for a different port to be used as long as both client and server agree on it.

The CVS server is not actually waiting for connections at that port - the server won't get started up until a connection actually arrives. Instead, the Unix inetd (InterNET Daemon) program is listening on that port, and needs to know that when it receives a connection request there, it should start up the CVS server and connect it to the incoming client.

This is accomplished by modifying inetd's configuration files: `/etc/services` and `/etc/inetd.conf`. The services file maps raw port numbers to service names and then inetd.conf tells inetd what to do for a given service name.

First, put a line like this into /etc/services (after checking to make sure it isn't already there):

         cvspserver	2401/tcp

Then in /etc/inetd.conf, put this:

         cvspserver stream tcp nowait root /usr/local/bin/cvs cvs \
            --allow-root=/usr/local/newrepos pserver

(In the actual file, this should be all one long line, with no backslash.) If your system uses tcpwrappers, you may want to use something like this instead:

         cvspserver stream tcp nowait root /usr/sbin/tcpd /usr/local/bin/cvs \
            --allow-root=/usr/local/newrepos pserver

Now, restart inetd so it notices the changes to its configuration files (if you don't know how to restart the daemon, just reboot the machine - that will work too).

That's enough to permit connections, but you'll also want to set up special CVS passwords - separate from the users' regular login passwords - so people can access the repository without compromising overall system security.

The CVS password file is CVSROOT/passwd in the repository. It was not created by default when you ran cvs init, because CVS doesn't know for sure that you'll be using pserver. Even if the password file had been created, CVS would have no way of knowing what usernames and passwords to create. So, you'll have to create one yourself; here's a sample CVSRoot/passwd file:

         kfogel:rKa5jzULzmhOo
         anonymous:XR4EZcEs0szik
         melissa:tGX1fS8sun6rY:pubcvs

The format is as simple as it looks. Each line is:

         <USERNAME>:<ENCRYPTED_PASSWORD>:<OPTIONAL_SYSTEM_USERNAME>

The extra colon followed by an optional system username tells CVS that connections authenticated with USERNAME should run as the system account SYSTEM_USERNAME - in other words, that CVS session would only be able to do things in the repository that someone logged in as SYSTEM_USERNAME could do.

If no system username is given, USERNAME must match an actual login account name on the system, and the session will run with that user's permissions. In either case, the encrypted password should not be the same as the user's actual login password. It should be an independent password used only for CVS pserver connections.

The password is encrypted using the same algorithm as the standard Unix system passwords stored in /etc/passwd. You may be wondering at this point, how does one acquire an encrypted version of a password? For Unix system passwords, the passwd command takes care of the encryption in /etc/passwd for you. Unfortunately, there is no corresponding cvs passwd command (it has been proposed several times, but no one's gotten around to writing it - perhaps you'll do it?).

This is an inconvenience, but only a slight one. If nothing else, you can always temporarily change a regular user's system password using passwd, cut and paste the encrypted text from /etc/passwd into CVSROOT/passwd, and then restore the old password (note that on some systems, the encrypted passwords are found in /etc/shadow and are readable only by root.)

That scheme is workable but rather cumbersome. It would be much easier to have a command-line utility that takes a plain text password as its argument and outputs the encrypted version. Here is such a tool, written in Perl:

         #!/usr/bin/perl

         srand (time());
         my $randletter = "(int (rand (26)) + (int (rand (1) + .5) % 2 ? 65 : 97))";
         my $salt = sprintf ("%c%c", eval $randletter, eval $randletter);
         my $plaintext = shift;
         my $crypttext = crypt ($plaintext, $salt);

         print "${crypttext}\n";

I keep the preceding script in `/usr/local/bin/cryptout.pl`:

         floss$ ls -l /usr/local/bin/cryptout.pl

         -rwxr-xr-x   1   root   root   265  Jun 14 20:41 /usr/local/bin/cryptout.pl
         floss$ cryptout.pl "some text"
         sB3A79YDX5L4s

         floss$

If I took the output of this example and used it to create the following entry in CVSROOT/passwd

         jrandom:sB3A79YDX5L4s:craig

then someone could connect to the repository with the following command:

         remote$ cvs -d :pserver:jrandom@floss.red-bean.com:/usr/local/newrepos login

They could then type `some text` as their password and thereafter be able to execute CVS commands with the same access privileges as the system user `craig`.

If someone attempts to authenticate with a username and password that don't appear in CVSROOT/passwd, CVS will check to see if that username and password are present in /etc/passwd. If they are (and if the password matches, of course), CVS will grant access. It behaves this way for the administrator's convenience, so that separate CVSROOT/passwd entries don't have to be set up for regular system users. However, this behavior is also a security hole, because it means that if one of those users does connect to the CVS server, her regular login password will have crossed over the network in cleartext, potentially vulnerable to the eyes of password sniffers. A bit further on, you'll learn how to turn off this "fallback" behavior, so that CVS consults only its own passwd file. Whether you leave it on or off, you should probably force any CVS users who also have login accounts to maintain different passwords for the two functions.

Although the passwd file authenticates for the whole repository, with a little extra work you can still use it to grant project-specific access. Here's one method:

Suppose you want to grant some remote developers access to project `foo`, and others access to project `bar`, and you don't want developers from one project to have commit access to the other. You can accomplish this by creating project-specific user accounts and groups on the system and then mapping to those accounts in the CVSROOT/passwd file.

Here's the relevant excerpt from /etc/passwd

         cvs-foo:*:600:600:Public CVS Account for Project Foo:/usr/local/cvs:/bin/false
         cvs-bar:*:601:601:Public CVS Account for Project Bar:/usr/local/cvs:/bin/false

and from /etc/group

         cvs-foo:*:600:cvs-foo
         cvs-bar:*:601:cvs-bar

and, finally, CVSROOT/passwd:

         kcunderh:rKa5jzULzmhOo:cvs-foo
         jmankoff:tGX1fS8sun6rY:cvs-foo
         brebard:cAXVPNZN6uFH2:cvs-foo
         xwang:qp5lsf7nzRzfs:cvs-foo
         dstone:JDNNF6HeX/yLw:cvs-bar
         twp:glUHEM8KhcbO6:cvs-bar
         ffranklin:cG6/6yXbS9BHI:cvs-bar
         yyang:YoEqcCeCUq1vQ:cvs-bar

Some of the CVS usernames map onto the system user account `cvs-foo` and some onto `cvs-bar`. Because CVS runs under the user ID of the system account, you just have to make sure that the relevant parts of the repository are writeable only by the appropriate users and groups. If you just make sure that the user accounts are locked down pretty tight (no valid login password, `/bin/false` as the shell), then this system is reasonably secure (but see later in this chapter about CVSROOT permissions!). Also, CVS does record changes and log messages under the CVS username, not the system username, so you can still tell who is responsible for a given change.

Node: Anonymous Access, Next: Repository Structure, Previous: The Password-Authenticating Server, Up: Repository Administration

### Anonymous Access

So far we've only seen how to use the password-authenticating server to grant normal full access to the repository (although admittedly one can restrict that access through carefully arranged Unix file permissions). Turning this into anonymous, read-only access is a simple step: You just have to add a new file, or possibly two, in CVSROOT/. The files' names are `readers` and `writers` - the former containing a list of usernames who can only read the repository, the latter users who can read and write.

If you list a username in CVSROOT/readers, that user will have only read access to all projects in the repository. If you list a username in CVSROOT/writers, that user will have write access, and every pserver user not listed in writers will have read-only access (that is, if the writers file exists at all, it implies read-only access for all those not listed in it). If the same username is listed in both files, CVS resolves the conflict in the more conservative way: the user will have read-only access.

The format of the files is very simple: one user per line (don't forget to put a newline after the last user). Here is a sample readers file:

         anonymous
         splotnik
         guest
         jbrowse

Note that the files apply to CVS usernames, not system usernames. If you use user aliasing in the CVSROOT/passwd file (putting a system username after a second colon), the leftmost username is the one to list in a readers or writers file.

Just to be painfully accurate about it, here is a formal description of the server's behavior in deciding whether to grant read-only or read-write access:

If a readers file exists and this user is listed in it, then she gets read-only access. If a writers file exists and this user is not listed in it, then she also gets read-only access (this is true even if a readers file exists but that person is not listed there). If that person is listed in both, she gets read-only access. In all other cases, that person gets full read-write access.

Thus, a typical repository with anonymous CVS access has this (or something like it) in CVSROOT/passwd

         anonymous:XR4EZcEs0szik

this (or something like it) in /etc/passwd

         anonymous:!:1729:105:Anonymous CVS User:/usr/local/newrepos:/bin/false

and this in CVSROOT/readers:

         anonymous

And, of course, the aforementioned setup in /etc/services and /etc/inetd.conf. That's all there is to it!

Note that some older Unix systems don't support usernames longer than eight characters. One way to get around this would be to call the user `anon` instead of `anonymous` in CVSROOT/passwd and in the system files, because people often assume that anon is short for anonymous anyway. But it might be better to put something like this into the CVSROOT/passwd file

         anonymous:XR4EZcEs0szik:cvsanon

(and then of course use `cvsanon` in the system files). That way, you'd be able to publish a repository address that uses `anonymous`, which is more or less standard now. People accessing the repository with

         cvs -d :pserver:anonymous@cvs.foobar.com:/usr/local/newrepos (etc...)

would actually run on the server as cvsanon (or whatever). But they wouldn't need to know or care about how things are set up on the server side - they'd only see the published address.

Node: Repository Structure, Next: RCS Format, Previous: Anonymous Access, Up: Repository Administration

### Repository Structure

The new repository still has no projects in it. Let's re-run the initial import from An Overview of CVS, watching what happens to the repository. (For simplicity's sake, all commands will assume that the CVSROOT environment variable has been set to /usr/local/newrepos, so there's no need to specify the repository with -d on imports and checkouts.)

         floss$ ls /usr/local/newrepos
         CVSROOT/
         floss$ pwd
         /home/jrandom/src/
         floss$ ls
         myproj/
         floss$ cd myproj
         floss$ cvs import -m "initial import into CVS" myproj jrandom start
         N myproj/README.txt
         N myproj/hello.c
         cvs import: Importing /usr/local/newrepos/myproj/a-subdir
         N myproj/a-subdir/whatever.c
         cvs import: Importing /usr/local/newrepos/myproj/a-subdir/subsubdir
         N myproj/a-subdir/subsubdir/fish.c
         cvs import: Importing /usr/local/newrepos/myproj/b-subdir
         N myproj/b-subdir/random.c

         No conflicts created by this import

         floss$ ls /usr/local/newrepos
         CVSROOT/  myproj/
         floss$ cd /usr/local/newrepos/myproj
         floss$ ls
         README.txt,v  a-subdir/     b-subdir/	  hello.c,v
         floss$ cd a-subdir
         floss$ ls
         subsubdir/    whatever.c,v
         floss$ cd ..

         floss$

Before the import, the repository contained only its administrative area, CVSROOT. After the import, a new directory - `myproj` - appeared. The files and subdirectories inside that new directory look suspiciously like the project we imported, except that the files have the suffix `,v`. These are RCS-format version control files (the `,v` stands for "version"), and they are the backbone of the repository. Each RCS file stores the revision history of its corresponding file in the project, including all branches and tags.

Node: RCS Format, Next: What Happens When You Remove A File, Previous: Repository Structure, Up: Repository Administration

### RCS Format

You do not need to know any of the RCS format to use CVS (although there is an excellent writeup included with the source distribution, see doc/RCSFILES). However, a basic understanding of the format can be of immense help in troubleshooting CVS problems, so we'll take a brief peek into one of the files, `hello.c,v`. Here are its contents:

         head     1.1;
         branch   1.1.1;
         access   ;
         symbols  start:1.1.1.1 jrandom:1.1.1;
         locks    ; strict;
         comment  @ * @;

         1.1
         date     99.06.20.17.47.26;  author jrandom;  state Exp;
         branches 1.1.1.1;
         next;

         1.1.1.1
         date     99.06.20.17.47.26;  author jrandom;  state Exp;
         branches ;
         next;

         desc
         @@

         1.1
         log
         @Initial revision
         @
         text
         @#include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
         }
         @

         1.1.1.1
         log
         @initial import into CVS
         @
         text
         @@

Whew! Most of that you can ignore; don't worry about the relationship between 1.1 and 1.1.1.1, for example, or the implied 1.1.1 branch - they aren't really significant from a user's or even an administrator's point of view. What you should try to grok is the overall format. At the top is a collection of header fields:

         head     1.1;
         branch   1.1.1;
         access   ;
         symbols  start:1.1.1.1 jrandom:1.1.1;
         locks    ; strict;
         comment  @ * @;

Farther down in the file are groups of meta-information about each revision (but still not showing the contents of that revision), such as:

         1.1
         date     99.06.20.17.47.26;  author jrandom;  state Exp;
         branches 1.1.1.1;
         next     ;

And finally, the log message and text of an actual revision:

         1.1
         log
         @Initial revision
         @
         text
         @#include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
         }
         @

         1.1.1.1
         log
         @initial import into CVS
         @
         text
         @@

If you look closely, you'll see that the first revision's contents are stored under the heading 1.1, but that the log message there is "Initial revision", whereas the log message we actually used at import time was "initial import into CVS", which appears farther down, under `Revision 1.1.1.1`. You don't need to worry about this discrepancy right now. It happens because imports are a special circumstance: In order to make repeated imports into the same project have a useful effect, import actually places the initial revision on both the main trunk and on a special branch (the reasons for this will become clearer when we look at vendor branches in Advanced CVS). For now, you can treat `1.1` and `1.1.1.1` as the same thing.

The file becomes even more revealing after we commit the first modification to hello.c:

         floss$ cvs -Q co myproj
         floss$ cd myproj
         floss$ emacs hello.c
             (make some changes to the file)

         floss$ cvs ci -m "print goodbye too"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in hello.c;
         /usr/local/newrepos/myproj/hello.c,v  <--  hello.c
         new revision: 1.2; previous revision: 1.1
         done

If you look at hello.c,v in the repository now, you can see the effect of the commit:

         head  1.2;
         access;
         symbols
               start:1.1.1.1 jrandom:1.1.1;
         locks; strict;
         comment   @ * @;

         1.2
         date   99.06.21.01.49.40;   author jrandom;   state Exp;
         branches;
         next   1.1;

         1.1
         date   99.06.20.17.47.26;   author jrandom;   state Exp;
         branches
                1.1.1.1;
         next   ;

         1.1.1.1
         date   99.06.20.17.47.26;   author jrandom;   state Exp;
         branches;
         next   ;

         desc
         @@

         1.2
         log
         @print goodbye too
         @
         text
         @#include <stdio.h>

         void
         main ()
         {
           printf ("Hello, world!\n");
           printf ("Goodbye, world!\n");
         }
         @

         1.1
         log
         @Initial revision
         @
         text
         @d7 1
         @

         1.1.1.1
         log
         @initial import into CVS
         @
         text
         @@

Now the full contents of Revision 1.2 are stored in the file, and the text for Revision 1.1 has been replaced with the cryptic formula:

         d7 1

The `d7 1` is a diff code that means "starting at line 7, delete 1 line". In other words, to derive Revision 1.1, delete line 7 from Revision 1.2! Try working through it yourself. You'll see that it does indeed produce Revision 1.1 - it simply does away with the line we added to the file.

This demonstrates the basic principle of RCS format: It stores only the differences between revisions, thereby saving a lot of space compared with storing each revision in full. To go backwards from the most recent revision to the previous one, it patches the later revision using the stored diff. Of course, this means that the further back you travel in the revision history, the more patch operations must be performed (for example, if the file is on Revision 1.7 and CVS is asked to retrieve Revision 1.4, it has to produce 1.6 by patching backwards from 1.7, then 1.5 by patching 1.6, then 1.4 by patching 1.5). Fortunately, old revisions are also the ones least often retrieved, so the RCS system works out pretty well in practice: The more recent the revision, the cheaper it is to obtain.

As for the header information at the top of the file, you don't need to know what all of it means. However, the effects of certain operations show up very clearly in the headers, and a passing familiarity with them may prove useful.

When you commit a new revision on the trunk, the `head` label is updated (note how it became 1.2 in the preceding example, when the second revision to hello.c was committed). When you add a file as binary or tag it, those operations are recorded in the headers as well. As an example, we'll add foo.jpg as a binary file and then tag it a couple of times:

         floss$ cvs add -kb foo.jpg
         cvs add: scheduling file 'foo.jpg' for addition
         cvs add: use 'cvs commit' to add this file permanently
         floss$ cvs -q commit -m "added a random image; ask jrandom@red-bean.com why"
         RCS file: /usr/local/newrepos/myproj/foo.jpg,v
         done
         Checking in foo.jpg;
         /usr/local/newrepos/myproj/foo.jpg,v  <--  foo.jpg
         initial revision: 1.1
         done
         floss$ cvs tag some_random_tag foo.jpg
         T foo.jpg
         floss$ cvs tag ANOTHER-TAG foo.jpg
         T foo.jpg
         floss$

Now examine the header section of foo.jpg,v in the repository:

         head   1.1;
         access;
         symbols
               ANOTHER-TAG:1.1
               some_random_tag:1.1;
         locks; strict;
         comment   @# @;
         expand	@b@;

Notice the b in the expand line at the end - it's due to our having used the -kb flag when adding the file, and means the file won't undergo any keyword or newline expansions, which would normally occur during checkouts and updates if it were a regular text file. The tags appear in the symbols section, one tag per line - both of them are attached to the first revision, since that's what was tagged both times. (This also helps explain why tag names can only contain letters, numbers, hyphens, and underscores. If the tag itself contained colons or dots, the RCS file's record of it might be ambiguous, because there would be no way to find the textual boundary between the tag and the revision to which it is attached.)

### RCS Format Always Quotes @ Signs

The `@` symbol is used as a field delimiter in RCS files, which means that if one appears in the text of a file or in a log message, it must be quoted (otherwise, CVS would incorrectly interpret it as marking the end of that field). It is quoted by doubling - that is, CVS always interprets `@@` as "literal @ sign", never as "end of current field". When we committed foo.jpg, the log message was

         "added a random image; ask jrandom@red-bean.com why"

which is stored in foo.jpg,v like this:

         1.1
         log
         @added a random image; ask jrandom@@red-bean.com why
         @

The @ sign in jrandom@@red-bean.com will be automatically unquoted whenever CVS retrieves the log message:

         floss$ cvs log foo.jpg
         RCS file: /usr/local/newrepos/myproj/foo.jpg,v
         Working file: foo.jpg
         head: 1.1
         branch:
         locks: strict
         access list:
         symbolic names:
               ANOTHER-TAG: 1.1
               some_random_tag: 1.1
         keyword substitution: b
         total revisions: 1;	selected revisions: 1
         description:
         ----------------------------
         revision 1.1
         date: 1999/06/21 02:56:18;  author: jrandom;  state: Exp;
         added a random image; ask jrandom@red-bean.com why
         ============================================================================

         floss$

The only reason you should care is that if you ever find yourself hand-editing RCS files (a rare circumstance, but not unheard of), you must remember to use double @ signs in revision contents and log messages. If you don't, the RCS file will be corrupt and will probably exhibit strange and undesirable behaviors.

Speaking of hand-editing RCS files, don't be fooled by the permissions in the repository:

         floss$ ls -l
         total 6
         -r--r--r--   1 jrandom   users         410 Jun 20 12:47 README.txt,v
         drwxrwxr-x   3 jrandom   users        1024 Jun 20 21:56 a-subdir/
         drwxrwxr-x   2 jrandom   users        1024 Jun 20 21:56 b-subdir/
         -r--r--r--   1 jrandom   users         937 Jun 20 21:56 foo.jpg,v
         -r--r--r--   1 jrandom   users         564 Jun 20 21:11 hello.c,v

         floss$

(For those not fluent in Unix ls output, the `-r--r--r--` lines on the left essentially mean that the files can be read but not changed.) Although the files appear to be read-only for everyone, the directory permissions must also be taken into account:

         floss$ ls -ld .
         drwxrwxr-x   4 jrandom   users        1024 Jun 20 22:16 ./
         floss$

The myproj/ directory itself - and its subdirectories - are all writeable by the owner (jrandom) and the group (users). This means that CVS (running as jrandom, or as anyone in the users group) can create and delete files in those directories, even if it can't directly edit files already present. CVS edits an RCS file by making a separate copy of it, so you should also make all of your changes in a temporary copy, and then replace the existing RCS file with the new one. (But please don't ask why the files themselves are read-only - there are historical reasons for that, having to do with the way RCS works when run as a standalone program.)

Incidentally, having the files' group be `users` is probably not what you want, considering that the top-level directory of the repository was explicitly assigned group `cvs`. You can correct the problem by running this command inside the repository:

         floss$ cd /usr/local/newrepos
         floss$ chgrp -R cvs myproj

The usual Unix file-creation rules govern which group is assigned to new files that appear in the repository, so once in a while you may need to run chgrp or chmod on certain files or directories in the repository (setting the SGID bit with `chmod g+s` is often a good strategy: it makes children of a directory inherit the directory's group ownership, which is usually what you want in the repository). There are no hard and fast rules about how you should structure repository permissions; it just depends on who is working on what projects.

Node: What Happens When You Remove A File, Next: The CVSROOT/ Administrative Directory, Previous: RCS Format, Up: Repository Administration

### What Happens When You Remove A File

When you remove a file from a project, it doesn't just disappear. CVS must be able to retrieve such files when you request an old snapshot of the project. Instead, the file gets put in the `Attic`, literally:

         floss$ pwd
         /home/jrandom/src/myproj
         floss$ ls /usr/local/newrepos/myproj/
         README.txt,v  a-subdir/     b-subdir/     foo.jpg,v   hello.c,v
         floss$ rm foo.jpg
         floss$ cvs rm foo.jpg
         cvs remove: scheduling 'foo.jpg' for removal
         cvs remove: use 'cvs commit' to remove this file permanently
         floss$ cvs ci -m "Removed foo.jpg" foo.jpg
         Removing foo.jpg;
         /usr/local/newrepos/myproj/foo.jpg,v  <--  foo.jpg
         new revision: delete; previous revision: 1.1
         done
         floss$ cd /usr/local/newrepos/myproj/
         floss$ ls
         Attic/      README.txt,v  a-subdir/     b-subdir/   hello.c,v
         floss$ cd Attic
         floss$ ls
         foo.jpg,v
         floss$

In each repository directory of a project, the presence of an `Attic/` subdirectory means that at least one file has been removed from that directory (this means that you shouldn't use directories named Attic in your projects). CVS doesn't merely move the RCS file into Attic/, however; it also commits a new revision into the file, with a special revision state of `dead`. Here's the relevant section from Attic/foo.jpg,v:

         1.2
         date   99.06.21.03.38.07;   author jrandom;   state dead;
         branches;
         next	1.1;

If the file is later brought back to life, CVS has a way of recording that it was dead at some point in the past and is now alive again.

This means that if you want to restore a removed file, you can't just take it out of the Attic/ and put it back into the project. Instead, you have to do something like this in a working copy:

         floss$ pwd
         /home/jrandom/src/myproj
         floss$ cvs -Q update -p -r 1.1 foo.jpg > foo.jpg
         floss$ ls
         CVS/       README.txt   a-subdir/   b-subdir/   foo.jpg     hello.c
         floss$ cvs add -kb foo.jpg
         cvs add: re-adding file foo.jpg (in place of dead revision 1.2)
         cvs add: use 'cvs commit' to add this file permanently
         floss$ cvs ci -m "revived jpg image" foo.jpg
         Checking in foo.jpg;
         /usr/local/newrepos/myproj/foo.jpg,v  <-- foo.jpg
         new revision: 1.3; previous revision: 1.2
         done
         floss$ cd /usr/local/newrepos/myproj/
         floss$ ls
         Attic/	      a-subdir/     foo.jpg,v
         README.txt,v  b-subdir/     hello.c,v
         floss$ ls Attic/
         floss$

There's a lot more to know about RCS format, but this is sufficient for a CVS adminstrator to maintain a repository. It's quite rare to actually edit an RCS file; you'll usually just have to tweak file permissions in the repository, at least if my own experience is any guide. Nevertheless, when CVS starts behaving truly weirdly (rare, but not completely outside the realm of possibility), you may want to actually look inside the RCS files to figure out what's going on.

Node: The CVSROOT/ Administrative Directory, Next: Commit Emails, Previous: What Happens When You Remove A File, Up: Repository Administration

### The CVSROOT/ Administrative Directory

The files in newrepos/CVSROOT/ are not part of any project, but are used to control CVS's behavior in the repository. The best way to edit those files is to check out a working copy of CVSROOT, just like a regular project:

         floss$ cvs co CVSROOT
         cvs checkout: Updating CVSROOT
         U CVSROOT/checkoutlist
         U CVSROOT/commitinfo
         U CVSROOT/config
         U CVSROOT/cvswrappers
         U CVSROOT/editinfo
         U CVSROOT/loginfo
         U CVSROOT/modules
         U CVSROOT/notify
         U CVSROOT/rcsinfo
         U CVSROOT/taginfo
         U CVSROOT/verifymsg
         floss$

We'll take the files in their approximate order of importance. Note that each of the files comes with an explanatory comment at the beginning (the comment convention is the same across all of them: A `#` sign at the beginning of the line signifies a comment, and CVS ignores such lines when parsing the files). Remember that any change you make to the administrative files in your checked out working copy won't affect CVS's behavior until you commit the changes.

If you're extremely security conscious, you may want to arrange the Unix-level permissions on CVSROOT to be different from permissions elsewhere in the repository, in order to have fine-grained control over who can commit changes to CVSROOT. As you'll see a little later, being able to modify the files in CVSROOT essentially gives any CVS user - even remote ones - the ability to run arbitrary commands on the repository machine.

Node: The config File, Next: The modules File, Up: The CVSROOT/ Administrative Directory

### The config File

The config file allows you to configure certain global behavioral parameters. It follows a very strict format

         PARAMETER=VALUE
         (etc)

with no extra spaces allowed. For example, here is a possible config file:

         SystemAuth=yes
         TopLevelAdmin=no
         PreservePermissions=no

(An absent entry would be equivalent to `no`.)

The `SystemAuth` parameter governs whether CVS should look in the system passwd file if it fails to find a given username in the CVSROOT/passwd file. CVS distributions are shipped with this set to `no` to be conservative about your system's security.

`TopLevelAdmin` tells CVS whether to make a sibling CVS/ directory when it checks out a working copy. This CVS/ directory would not be inside the working copy, but rather next to it. It might be convenient to turn this on if you tend (and your repository's users tend) to check out many different projects from the same repository. Otherwise, you should leave it off, as it can be disconcerting to see an extra CVS/ directory appear where you don't expect it.

`PreservePermissions` governs whether to preserve file permissions and similar metadata in the revision history. This is a somewhat obscure feature that probably isn't worth describing in detail. See the node Special Files in the Cederqvist if you're interested (node is Texinfo-speak for a particular location within an Info document. To go to a node while reading Info, just type `g` followed by the name of the node, from anywhere inside the document).

`LockDir` is also a rarely used feature. In special circumstances, you may want to tell CVS to create its lockfiles somewhere other than directly in the project subdirectories, in order to avoid permission problems. These lockfiles keep CVS from tripping over itself when multiple operations are performed on the same repository directory simultaneously. Generally, you never need to worry about them, but sometimes users may have trouble updating or checking out from a repository directory because they're unable to create a lockfile (even on read-only operations, CVS needs to create a lockfile to avoid situations where it could end up reading while another invocation of CVS is writing). The usual fix for this is to change repository permissions, but when that's not feasible, the LockDir parameter can come in handy.

There are no other parameters at this time, but future versions of CVS may add new ones; you should always check the Cederqvist or the distribution config file itself for updates.

Node: The modules File, Next: The commitinfo And loginfo And rcsinfo Files, Previous: The config File, Up: The CVSROOT/ Administrative Directory

### The modules File

In modules, you can define aliases and alternate groupings for projects in the repository. The most basic module line is of the form:

         MODULE_NAME   DIRECTORY_IN_REPOSITORY

for example,

         mp    myproj
         asub  myproj/a-subdir

(The paths given on the right are relative to the top of the repository.) This gives developers an alternate name by which to check out a project or a portion of a project:

         floss$ cvs co mp
         cvs checkout: Updating mp
         U mp/README.txt
         U mp/foo.jpg
         U mp/hello.c
         cvs checkout: Updating mp/a-subdir
         U mp/a-subdir/whatever.c
         cvs checkout: Updating mp/a-subdir/subsubdir
         U mp/a-subdir/subsubdir/fish.c
         cvs checkout: Updating mp/b-subdir
         U mp/b-subdir/random.c

or

         floss$ cvs -d /usr/local/newrepos/ co asub
         cvs checkout: Updating asub
         U asub/whatever.c
         cvs checkout: Updating asub/subsubdir
         U asub/subsubdir/fish.c

Notice how in both cases the module's name became the name of the directory created for the working copy. In the case of asub, it didn't even bother with the intermediate myproj/ directory, but created a top-level asub/ instead, even though it came from myproj/a-subdir in the repository. Updates, commits, and all other CVS commands will behave normally in those working copies - the only thing unusual about them are their names.

By putting file names after the directory name, you can define a module consisting of just some of the files in a given repository directory. For example

         readme  myproj  README.txt

and

         no-readme  myproj  hello.c  foo.jpg

would permit the following checkouts, respectively:

         floss$ cvs -q co readme
         U readme/README.txt
         floss$ cvs -q co no-readme
         U no-readme/hello.c
         U no-readme/foo.jpg
         floss$

You can define a module that will include multiple repository directories by using the -a (for `alias`) flag, but note that the directories will get them checked out under their original names. For example, this line

         twoproj  -a  myproj  yourproj

would allow you to do this (assuming that both myproj/ and yourproj/ are in the repository):

         floss$ cvs co twoproj
         U myproj/README.txt
         U myproj/foo.jpg
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         U yourproj/README
         U yourproj/foo.c
         U yourproj/some-subdir/file1.c
         U yourproj/some-subdir/file2.c
         U yourproj/some-subdir/another-subdir/blah.c

The name `twoproj` was a convenient handle to pull in both projects, but it didn't affect the names of the working copies. (There is no requirement that alias modules refer to multiple directories, by the way; we could have omitted twoproj, in which case myproj would still have been checked out under the name `myproj`.)

Modules can even refer to other modules, by prefixing them with an ampersand:

         mp    myproj
         asub  myproj/a-subdir
         twoproj -a myproj yourproj
         tp  &twoproj

Doing a checkout of `tp` would have exactly the same result as the checkout of `twoproj` did.

There are a few other tricks you can do with modules, most of them less frequently used than the ones just presented. See the node modules in the Cederqvist for information about them.

Node: The commitinfo And loginfo And rcsinfo Files, Next: The verifymsg And rcsinfo Files, Previous: The modules File, Up: The CVSROOT/ Administrative Directory

### The commitinfo And loginfo And rcsinfo Files

Most of the other administrative files provide programmatic hooks into various parts of the commit process (for example, the ability to validate log messages or file states before permitting the commit, or the ability to notify a group of developers whenever a commit happens in a certain directory of the repository).

The files generally share a common syntax. Each line is of the form:

         REGULAR_EXPRESSION    PROGRAM_TO_RUN

The regular expression will be tested against the directory into which the commit is taking place (with the directory name relative to the top of the repository). If it matches, the designated program will be run. The program will be passed the names of each of the files in the commit; it can do whatever it likes with those names, including opening up the files and examining their contents. If the program returns with a nonzero exit status, the commit is prevented from taking place.

(Regular expressions are a system for concisely describing classes of strings. If you aren't familiar with regular expressions, you can get by with the following short summary: `foo` would match any file whose name contains the string `foo`; and `foo.*bar` would match any file whose name contains `foo`, followed by any number of characters, followed by the string `bar`. That's because normal substrings match themselves, but `.` and `*` are special. `.` matches any character, and `*` means match any number of the preceding character, including zero. The `^` and `$` signs mean match at the beginning and end of the string, respectively; thus, `^foo.*bar.*baz$` would match any string beginning with `foo`, containing `bar` somewhere in the middle, and ending with `baz`. That's all we'll go into here; this summary is a very abbreviated subset of full regular expression syntax.)

The commitinfo file is for generic hooks you want run on every commit. Here are some example commitinfo lines:

         ^a-subdir*     /usr/local/bin/check-asubdir.sh
         ou             /usr/local/bin/validate-project.pl

So any commit into myproj/a-subdir/ would match the first line, which would then run the check-asubdir.sh script. A commit in any project whose name (actual repository directory name, not necessarily module name) contained the string `ou` would run the validate-project.pl script, unless the commit had already matched the previous a-subdir line.

In place of a regular expression, the word `DEFAULT` or `ALL` may be used. The DEFAULT line (or the first DEFAULT line, if there are more than one) will be run if no regular expression matches, and each of the ALL lines will be run in addition to any other lines that may match.

The file names passed to the program do not refer to RCS files - they point to normal files, whose contents are exactly the same as the working-copy files being committed. The only unusual aspect is that CVS has them temporarily placed inside the repository, so they'll be available to programs running on the machine where the repository is located.

The loginfo file is similar to commitinfo, except that instead of acting on the files' contents, it acts on the log message. The left side of the loginfo file contains regular expressions, including possibly DEFAULT and ALL lines. The program invoked on the right side receives the log message on its standard input; it can do whatever it wants with that input.

The program on the right side can also take an arbitrary number of command-line arguments. One of those arguments can be a special `%` code, to be expanded by CVS at runtime, as follows:

         %s    ------>      name(s) of the file(s) being committed
         %V    ------>      revision number(s) before the commit
         %v    ------>      revision number(s) after the commit

The expansion always begins with the repository subdirectory (relative to the top of the repository), followed by the per-file information. For example, if the files committed were foo, bar, and baz, all in `myproj/a-subdir`, then `%s` would expand into

         myproj/a-subdir  foo  bar  baz

whereas `%V` would expand to show their old revision numbers

         myproj/a-subdir  1.7  1.134  1.12

and `%v` their new revision numbers:

         myproj/a-subdir  1.8  1.135  1.13

You can combine `%` expressions by enclosing them in curly braces following `%` sign - this will expand them into a series of comma-separated sublists, each containing the corresponding information for one file in the commit. For instance, `%{sv}` would expand to

         myproj/a-subdir  foo,1.8  bar,1.135  baz,1.13

and `%{sVv}` would expand to

         myproj/a-subdir  foo,1.7,1.8  bar,1.134,1.135  baz,1.12,1.13

(You may have to look carefully to distinguish the commas from the periods in those examples.)

Here is a sample loginfo file:

         ^myproj$   /usr/local/newrepos/CVSROOT/log.pl -m myproj-devel@foobar.com %s
         ou         /usr/local/bin/ou-notify.pl  %{sv}
         DEFAULT    /usr/local/bin/default-notify.pl  %{sVv}

In the first line, any commit in the myproj subdirectory of the repository invokes `log.pl`, passing it an email address (to which `log.pl` will send a mail containing the log message), followed by the repository, followed by all the files in the commit.

In the second line, any commit in a repository subdirectory containing the string `ou` will invoke the (imaginary) `ou-notify.pl` script, passing it the repository followed by the file names and new revision numbers of the files in the commit.

The third line invokes the (equally imaginary) `default-notify.pl` script for any commit that didn't match either of the two previous lines, passing it all possible information (path to repository, file names, old revisions, and new revisions).

Node: The verifymsg And rcsinfo Files, Next: The taginfo File, Previous: The commitinfo And loginfo And rcsinfo Files, Up: The CVSROOT/ Administrative Directory

### The verifymsg And rcsinfo Files

Sometimes you may just want a program to automatically verify that the log message conforms to a certain standard and to stop the commit if that standard is not met. This can be accomplished by using `verifymsg`, possibly with some help from `rcsinfo`.

The verifymsg file is the usual combination of regular expressions and programs. The program receives the log message on standard input; presumably it runs some checks to verify that the log message meets certain criteria, then it exits with status zero or nonzero. If the latter, the commit will fail.

Meanwhile, the left side of rcsinfo has the usual regular expressions, but the right side points to template files instead of programs. A template file might be something like this

         Condition:
         Fix:
         Comments:

or some other collection of fields that a developer is supposed to fill out to form a valid log message. The template is not very useful if everyone commits using the -m option explicitly, but many developers prefer not to do that. Instead, they run

         floss$ cvs commit

and wait for CVS to automatically fire up a text editor (as specified in the EDITOR environment variable). There they write a log message, then save the file and exit the editor, after which CVS continues with the commit.

In that scenario, an rcsinfo template would insert itself into the editor before the user starts typing, so the fields would be displayed along with a reminder to fill them in. Then when the user commits, the appropriate program in `verifymsg` is invoked. Presumably, it will check that the message does follow that format, and its exit status will reflect the results of its inquiry (with zero meaning success).

As an aid to the verification programs, the path to the template from the rcsinfo file is appended as the last argument to the program command line in `verifymsg`; that way, the program can base its verification process on the template itself, if desired.

Note that when someone checks out a working copy to a remote machine, the appropriate rcsinfo template file is sent to the client as well (it's stored in the CVS/ subdirectory of the working copy). However, this means that if the rcsinfo file on the server is changed after that, the client won't see the changes without re-checking out the project (merely doing an update won't work).

Note also that in the verifymsg file, the ALL keyword is not supported (although DEFAULT still is). This is to make it easier to override default verification scripts with subdirectory-specific ones.

Node: The taginfo File, Next: The cvswrappers File, Previous: The verifymsg And rcsinfo Files, Up: The CVSROOT/ Administrative Directory

### The taginfo File

What loginfo does for log messages, taginfo does for tags. The left side of taginfo is regular expressions, as usual, and the right side is programs. Each program is automatically handed arguments when CVS tag is invoked, in this order:

         arg 1:          tag name
         arg 2:          operation ("add" => tag, "mov" => tag -F, "del" => tag -d)
         arg 3:          repository
         arg 4, 5, etc:  file revision [file revision ...]

If the program returns nonzero, the tag is aborted.

We haven't covered the -F option to tag before now, but it's exactly what the above implies: a way to move a tag from one revision to another. For example, if the tag `Known_Working` is attached to Revision 1.7 of a file and you want it attached to Revision 1.11 instead, you'd do this

         cvs tag -r 1.11 -F Known_Working foo.c

which removes the tag from 1.7, or wherever it was previously in that file, and puts it at 1.11.

Node: The cvswrappers File, Next: The editinfo File, Previous: The taginfo File, Up: The CVSROOT/ Administrative Directory

### The cvswrappers File

The redundantly-named cvswrappers file gives you a way to specify that certain files should be treated as binary, based on their file name. CVS does not assume that all .jpg files are JPG image data, for example, so it doesn't automatically use -kb when adding JPG files. Nonetheless, certain projects would find it very useful to simply designate all JPG files as binary. Here is a line in cvswrappers to do that:

         *.jpg -k 'b'

The `b` is separate and in quotes because it's not the only possible RCS keyword expansion mode; one could also specify `o`, which means not to expand `$` sign keywords but to do newline conversion. However, `b` is the most common parameter.

There are a few other modes that can be specified from the wrappers file, but they're for such rare situations that they're probably not worth documenting here (translation: your author has never had to use them). See the node Wrappers in the Cederqvist if you're curious.

Node: The editinfo File, Next: The notify File, Previous: The cvswrappers File, Up: The CVSROOT/ Administrative Directory

### The editinfo File

This file is obsolete, even though it's still included in distributions. Just ignore it.

Node: The notify File, Next: The checkoutlist File, Previous: The editinfo File, Up: The CVSROOT/ Administrative Directory

### The notify File

This file is used in conjunction with CVS's `watch` features, which are described in Advanced CVS. Nothing about it will make sense until you understand what watches are (they're a useful but non-essential feature), so see Advanced CVS for details about this file and about watches.

Node: The checkoutlist File, Previous: The notify File, Up: The CVSROOT/ Administrative Directory

### The checkoutlist File

If you look inside CVSROOT/, you'll see that working copies of the files exist side by side with their RCS revision files:

         floss$ ls /usr/local/newrepos/CVSROOT
         checkoutlist     config,v       history     notify     taginfo
         checkoutlist,v   cvswrappers    loginfo     notify,v   taginfo,v
         commitinfo       cvswrappers,v  loginfo,v   passwd     verifymsg
         commitinfo,v     editinfo       modules     rcsinfo    verifymsg,v
         config           editinfo,v     modules,v   rcsinfo,v

         floss$

CVS only pays attention to the working versions, not the RCS files, when it's looking for guidance on how to behave. Therefore, whenever you commit your working copy of CVSROOT/ (which might, after all, even be checked out to a different machine), CVS automatically updates any changed files in the repository itself. You will know that this has happened because CVS will print a message at the end of such commits:

         floss$ cvs ci -m "added mp and asub modules" modules
         Checking in modules;
         /usr/local/newrepos/CVSROOT/modules,v  <--  modules
         new revision: 1.2; previous revision: 1.1
         done
         cvs commit: Rebuilding administrative file database

CVS automatically knows about the standard administrative files, and will rebuild them in CVSROOT/ as necessary. If you decide to put custom files in CVSROOT/ (such as programs or rcsinfo template files), you'll have to tell CVS explicitly to treat them the same way.

That's the purpose of the checkoutlist file. It has a different format from most of the files we've looked at so far

         FILENAME     ERROR_MESSAGE_IF_FILE_CANNOT_BE_CHECKED_OUT

for example,

         log.pl           unable to check out / update log.pl in CVSROOT

         bugfix.tmpl      unable to check out / update bugfix.tmpl in CVSROOT

Certain files in CVSROOT are traditionally not kept under revision control. One such is the history file, which keeps a running record of all actions in the repository, for use by the `cvs history` command (which lists checkout, update, and tag activity for a given file or project directory). Incidentally, if you just remove the `history` file, CVS will obligingly stop keeping that log.

Note: sometimes the history file is the cause of permission problems, and the easiest way to solve them is to either make it world-writeable or just remove it.

Another `unrevisioned` administrative file is passwd, the assumption being that having it checked out over the network might compromise the passwords (even though they're encrypted). You'll have to decide based on your own security situation whether you want to add passwd to checkoutlist or not; by default, it is not in checkoutlist.

Two final notes about the CVSROOT/ directory: It is possible, if you make a big enough mistake, to commit an administrative file that is broken in such a way as to prevent any commits from happening at all. If you do that, naturally you won't be able to commit a fixed version of the administrative file! The solution is to go in and hand-edit the repository's working copy of the administrative file to correct the problem; the whole repository may stay inaccessible until you do that.

Also, for security's sake, make sure your CVSROOT/ directory is only writeable by users you trust (by `trust`, I mean you trust both their intentions and their ability not to compromise their password). The `*info` files give people the ability to invoke arbitrary programs, so anyone who can commit or edit files in the CVSROOT/ directory can essentially run any command on the system. That's something you should always keep in mind.

Node: Commit Emails, Next: Finding Out More, Previous: The CVSROOT/ Administrative Directory, Up: Repository Administration

### Commit Emails

The loginfo file is how one sets up commit emails - automated emails that go out to everyone working on a project whenever a commit takes place. (It may seem counterintuitive that this is done in loginfo instead of commitinfo, but the point is that one wants to include the log message in the email). The program to do the mailing - `contrib/log.pl` in the CVS source distribution - can be installed anywhere on your system. I customarily put it in the repository's CVSROOT/ subdirectory, but that's just a matter of taste.

You may need to edit `log.pl` a bit to get it to work on your system, possibly changing the first line to point to your Perl interpreter, and maybe changing this line

         $mailcmd = "| Mail -s 'CVS update: $modulepath'";

to invoke your preferred mailer, which may or may not be named `Mail`. Once you've got it set the way you like it, you can put lines similar to these into your loginfo:

         listerizer CVSROOT/log.pl %s -f CVSROOT/commitlog -m listerizer@red-bean.com
         RoadMail   CVSROOT/log.pl %s -f CVSROOT/commitlog -m roadmail@red-bean.com
         bk/*score  CVSROOT/log.pl %s -f CVSROOT/commitlog -m \
                                                 bkscore-devel@red-bean.com

The `%s` expands to the names of the files being committed; the -f option to `log.pl` takes a file name, to which the log message will be appended (so CVSROOT/commitlog is an ever-growing file of log messages); and the -m flag takes an email address, to which `log.pl` will send a message about the commit. The address is usually a mailing list, but you can specify the -m option as many times as necessary in one log.pl command line.

Node: Finding Out More, Previous: Commit Emails, Up: Repository Administration

### Finding Out More

Although this chapter tries to give a complete introduction to installing and administering CVS, I've left out things that are either too rarely used to be worth mentioning or already well documented in the Cederqvist manual. The latter category includes setting up the other remote access methods: RSH/SSH, kserver (Kerberos 4), and GSSAPI (which includes Kerberos 5, among other things). It should be noted that nothing special needs to be done for RSH/SSH connections, other than making sure that the user in question can log into the repository machine using RSH or SSH. If they can and CVS is installed on both client and server, and they have the right permissions to use the repository directly from the server machine, then they should be able to access the repository remotely via the :ext: method.

Descriptions of certain specialized features of CVS have been deferred to later chapters, so they can be introduced in contexts where their usefulness is obvious. General CVS troubleshooting tips are found in Tips And Troubleshooting. Although it's not necessary to read the entire Cederqvist manual, you should familiarize yourself with it; it will be an invaluable reference tool. If for some reason you don't have Info working on your machine and don't want to print the manual, you can browse it online at http://durak.org/cvswebsites/doc/ or http://www.loria.fr/~molli/cvs/doc/cvs_toc.html.

Node: Advanced CVS, Next: Tips And Troubleshooting, Previous: Repository Administration, Up: Top

## Advanced CVS

Now that we've covered the basic concepts of CVS usage and repository administration, we'll look at how CVS can be incorporated into the entire process of development. The fundamental CVS working cycle - checkout, update, commit, update, commit, and so on - was demonstrated by the examples in An Overview of CVS. This chapter elaborates on the cycle and discusses how CVS can be used to help developers communicate, give overviews of project activity and history, isolate and reunite different branches of development, and automate frequently performed tasks. Some of the techniques covered introduce new CVS commands, but many merely explain better ways to use commands that you already know.

Node: Watches (CVS As Telephone), Next: Log Messages And Commit Emails, Up: Advanced CVS

### Watches (CVS As Telephone)

A major benefit of using CVS on a project is that it can function as a communications device as well as a record-keeper. This section concentrates on how CVS can be used to keep participants informed about what's going on in a project. As is true with other aspects of CVS, these features reward cooperation. The participants must want to be informed; if people choose not to use the communications features, there's nothing CVS can do about it.

Node: How Watches Work, Next: Enabling Watches In The Repository, Up: Watches (CVS As Telephone)

### How Watches Work

In its default behavior, CVS treats each working copy as an isolated sandbox. No one knows what you're doing in your working copy until you commit your changes. In turn, you don't know what others are doing in theirs - except via the usual methods of communication, such as shouting down the hallway, "Hey, I'm going to work on parse.c now. Let me know if you're editing it so we can avoid conflicts!"

This informality works for projects where people have a general idea of who's responsible for what. However, this process can break down when a large number of developers are active in all parts of a code base and want to avoid conflicts. In such cases, they frequently have to cross each others' areas of responsibility but can't shout down the hallway at each other because they're geographically distributed.

A feature of CVS called `watches` provides developers with a way to notify each other about who is working on what files at a given time. By "setting a watch" on a file, a developer can have CVS notify her if anyone else starts to work on that file. The notifications are normally sent via email, although it is possible to set up other notification methods.

To use watches, you must modify one or two files in the repository administrative area, and developers must add some extra steps to the usual checkout/update/commit cycle. The changes on the repository side are fairly simple: You may need to edit the `CVSROOT/notify` file so that CVS knows how notifications are to be performed. You may also have to add lines to the `CVSROOT/users` file, which supplies external email addresses.

On the working copy side, developers have to tell CVS which files they want to watch so that CVS can send them notifications when someone else starts editing those files. They also need to tell CVS when they start or stop editing a file, so CVS can send out notifications to others who may be watching. The following commands are used to implement these extra steps:

- cvs watch
- cvs edit
- cvs unedit

The command `watch` differs from the usual CVS command pattern in that it requires further subcommands, such as `cvs watch add...`, `cvs watch remove...`, and so on.

In the following example, we'll look at how to turn on watches in the repository and then how to use watches from the developer's side. The two example users, jrandom and qsmith, each have their own separate working copies of the same project; the working copies may even be on different machines. As usual, all examples assume that the $CVSROOT environment variable has already been set, so there's no need to pass -d <REPOS> to any CVS commands.

Node: Enabling Watches In The Repository, Next: Using Watches In Development, Previous: How Watches Work, Up: Watches (CVS As Telephone)

### Enabling Watches In The Repository

First, the CVSROOT/notify file must be edited to turn on email notification. One of the developers can do this, or the repository administrator can if the developers don't have permission to change the repository's administrative files. In any case, the first thing to do is check out the administrative area and edit the notify file:

         floss$ cvs -q co CVSROOT
         U CVSROOT/checkoutlist
         U CVSROOT/commitinfo
         U CVSROOT/config
         U CVSROOT/cvswrappers
         U CVSROOT/editinfo
         U CVSROOT/loginfo
         U CVSROOT/modules
         U CVSROOT/notify
         U CVSROOT/rcsinfo
         U CVSROOT/taginfo
         U CVSROOT/verifymsg
         floss$ cd CVSROOT
         floss$ emacs notify
         ...

When you edit the notify file for the first time, you'll see something like this:

         # The "notify" file controls where notifications from watches set by
         # "cvs watch add" or "cvs edit" are sent. The first entry on a line is
         # a regular expression which is tested against the directory that the
         # change is being made to, relative to the $CVSROOT. If it matches,
         # then the remainder of the line is a filter program that should contain
         # one occurrence of %s for the user to notify, and information on its
         # standard input.
         #
         # "ALL" or "DEFAULT" can be used in place of the regular expression.
         #
         # For example:
         # ALL mail %s -s "CVS notification"

All you really need to do is uncomment the last line by removing the initial `#` mark. Although the notify file provides the same flexible interface as the other administrative files, with regular expressions matching against directory names, the truth is that you almost never want to use any of that flexibility. The only reason to have multiple lines, with each line's regular expression matching a particular part of the repository, would be if you wanted to use a different notification method for each project. However, normal email is a perfectly good notification mechanism, so most projects just use that.

To specify email notification, the line

         ALL mail %s -s "CVS notification"

should work on any standard Unix machine. This command causes notifications to be sent as emails with the subject line `CVS notification` (the special expression ALL matches any directory, as usual). Having uncommented that line, commit the notify file so the repository is aware of the change:

         floss$ cvs ci -m "turned on watch notification"
         cvs commit: Examining .
         Checking in notify;
         /usr/local/newrepos/CVSROOT/notify,v  <--  notify
         new revision: 1.2; previous revision: 1.1
         done
         cvs commit: Rebuilding administrative file database
         floss$

Editing the notify file in this way may be all that you'll need to do for watches in the repository. However, if there are remote developers working on the project, you may need to edit the `CVSROOT/users` file, too. The purpose of the users file is to tell CVS where to send email notifications for those users who have external email addresses. The format of each line in the users file is:

         CVS_USERNAME:EMAIL_ADDRESS

For example,

         qsmith:quentinsmith@farawayplace.com

The CVS username at the beginning of the line corresponds to a CVS username in `CVSROOT/password` (if present and the pserver access method is being used), or failing that, the server-side system username of the person running CVS. Following the colon is an external email address to which CVS should send watch notifications for that user.

Unfortunately, as of this writing, the users file does not exist in the stock CVS distribution. Because it's an administrative file, you must not only create, cvs add, and commit it in the usual way, but also add it to `CVSROOT/checkoutlist` so that a checked-out copy is always maintained in the repository.

Here is a sample session demonstrating this:

         floss$ emacs checkoutlist
           ... (add the line for the users file) ...
         floss$ emacs users
           ... (add the line for qsmith) ...
         floss$ cvs add users
         floss$ cvs ci -m "added users to checkoutlist, qsmith to users"
         cvs commit: Examining .
         Checking in checkoutlist;
         /usr/local/newrepos/CVSROOT/checkoutlist,v  <--  checkoutlist
         new revision: 1.2; previous revision: 1.1
         done
         Checking in users;
         /usr/local/newrepos/CVSROOT/users,v  <--  users
         new revision: 1.2; previous revision: 1.1
         done
         cvs commit: Rebuilding administrative file database
         floss$

It's possible to use expanded-format email addresses in `CVSROOT/users`, but you have to be careful to encapsulate all whitespace within quotes. For example, the following will work

         qsmith:"Quentin Q. Smith <quentinsmith@farawayplace.com>"

or

         qsmith:'Quentin Q. Smith <quentinsmith@farawayplace.com>'

However, this will not work:

         qsmith:"Quentin Q. Smith" <quentinsmith@farawayplace.com>

When in doubt, you should test by running the command line given in the notify file manually. Just replace the `%s` in

         mail %s -s "CVS notification"

with what you have following the colon in users. If it works when you run it at a command prompt, it should work in the users file, too.

When it's over, the checkout file will look like this:

         # The "checkoutlist" file is used to support additional version controlled
         # administrative files in $CVSROOT/CVSROOT, such as template files.
         #
         # The first entry on a line is a filename which will be checked out from
         # the corresponding RCS file in the $CVSROOT/CVSROOT directory.
         # The remainder of the line is an error message to use if the file cannot
         # be checked out.
         #
         # File format:
         #
         #       [<whitespace>]<filename><whitespace><error message><end-of-line>
         #
         # comment lines begin with '#'

         users   Unable to check out 'users' file in CVSROOT.

The users file will look like this:

         qsmith:quentinsmith@farawayplace.com

Now that the repository is set up for watches, let's look at what developers need to do in their working copies.

Node: Using Watches In Development, Next: Ending An Editing Session, Previous: Enabling Watches In The Repository, Up: Watches (CVS As Telephone)

### Using Watches In Development

First, a developer checks out a working copy and adds herself to the list of watchers for one of the files in the project:

         floss$ whoami
         jrandom
         floss$ cvs -q co myproj
         U myproj/README.txt
         U myproj/foo.gif
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         floss$ cd myproj
         floss$ cvs watch add hello.c
         floss$

The last command, cvs watch add hello.c, tells CVS to notify jrandom if anyone else starts working on hello.c (that is, it adds jrandom to hello.c's watch list). For CVS to send notifications as soon as a file is being edited, the user who is editing it has to announce the fact by running cvs edit on the file first. CVS has no other way of knowing when someone starts working on a file. Once checkout is done, CVS isn't usually invoked until the next update or commit, which happens after the file has already been edited:

         paste$ whoami
         qsmith
         paste$ cvs -q co myproj
         U myproj/README.txt
         U myproj/foo.gif
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         paste$ cd myproj
         paste$ cvs edit hello.c
         paste$ emacs hello.c
         ...

When qsmith runs cvs edit hello.c, CVS looks at the watch list for hello.c, sees that jrandom is on it, and sends email to jrandom telling her that qsmith has started editing the file. The email even appears to come from qsmith:

         From: qsmith
         Subject: CVS notification
         To: jrandom
         Date: Sat, 17 Jul 1999 22:14:43 -0500

         myproj hello.c
         --
         Triggered edit watch on /usr/local/newrepos/myproj
         By qsmith

         Furthermore, every time that qsmith (or anyone) commits a new revision of hello.c, jrandom will receive another email:

         myproj hello.c
         --
         Triggered commit watch on /usr/local/newrepos/myproj
         By qsmith

After receiving these emails, jrandom may want to update hello.c immediately to see what qsmith has done, or perhaps she'll email qsmith to find out why he's working on that file. Note that nothing forced qsmith to remember to run cvs edit - presumably he did it because he wanted jrandom to know what he was up to (anyway, even if he forgot to do cvs edit, his commits would still trigger notifications). The reason to use cvs edit is that it notifies watchers before you start to work on a file. The watchers can contact you if they think there may be a conflict, before you've wasted a lot of time.

CVS assumes that anyone who runs cvs edit on a file wants to be added to the file's watch list, at least temporarily, in case someone else starts to edit it. When qsmith ran cvs edit, he became a watcher of hello.c. Both he and jrandom would have received notification if a third party had run cvs edit on that file (or committed it).

However, CVS also assumes that the person editing the file only wants to be on its watch list while he or she is editing it. Such users are taken off the watch list when they're done editing. If they prefer to be permanent watchers of the file, they would have to run cvs watch add. CVS makes a default assumption that someone is done editing when he or she commits a file (until the next time, anyway).

Anyone who gets on a file's watch list solely by virtue of having run `cvs edit` on that file is known as a temporary watcher and is taken off the watch list as soon as she commits a change to the file. If she wants to edit it again, she has to rerun `cvs edit`.

CVS's assumption that the first commit ends the editing session is only a best guess, of course, because CVS doesn't know how many commits the person will need to finish their changes. The guess is probably accurate for one-off changes - changes where someone just needs to make one quick fix to a file and commit it. For more prolonged editing sessions involving several commits, users should add themselves permanently to the file's watch list:

         paste$ cvs watch add hello.c
         paste$ cvs edit hello.c
         paste$ emacs hello.c
         ...
         paste$ cvs commit -m "print hello in Sanskrit"

Even after the commit, qsmith remains a watcher of hello.c because he ran watch add on it. (By the way, qsmith will not receive notification of his own edits; only other watchers will. CVS is smart enough not to notify you about actions that you took.)

Node: Ending An Editing Session, Next: Controlling What Actions Are Watched, Previous: Using Watches In Development, Up: Watches (CVS As Telephone)

### Ending An Editing Session

If you don't want to commit but want to explicitly end an editing session, you can do so by running cvs unedit:

         paste$ cvs unedit hello.c

But beware! This does more than just notify all watchers that you're done editing - it also offers to revert any uncommitted changes that you've made to the file:

         paste$ cvs unedit hello.c
         hello.c has been modified; revert changes? y
         paste$

If you answer `y`, CVS undoes all your changes and notifies watchers that you're not editing the file anymore. If you answer `n`, CVS keeps your changes and also keeps you registered as an editor of the file (so no notification goes out - in fact, it's as if you never ran `cvs unedit` at all). The possibility of CVS undoing all of your changes at a single keystroke is a bit scary, but the rationale is easy to understand: If you declare to the world that you're ending an editing session, then any changes you haven't committed are probably changes you don't mean to keep. At least, that's the way CVS sees it. Needless to say, be careful!

Node: Controlling What Actions Are Watched, Next: Finding Out Who Is Watching What, Previous: Ending An Editing Session, Up: Watches (CVS As Telephone)

### Controlling What Actions Are Watched

By default, watchers are notified about three kinds of action: edits, commits, and unedits. However, if you only want to be notified about, say, commits, you can restrict notifications by adjusting your watch with the -a flag (a for action):

         floss$ cvs watch add -a commit hello.c

Or if you want to watch edits and commits but don't care about unedits, you could pass the -a flag twice:

         floss$ cvs watch add -a edit -a commit hello.c

Adding a watch with the -a flag will never cause any of your existing watches to be removed. If you were watching for all three kinds of actions on hello.c, running

         floss$ cvs watch add -a commit hello.c

has no effect - you'll still be a watcher for all three actions. To remove watches, you should run

         floss$ cvs watch remove hello.c

which is similar to add in that, by default, it removes your watches for all three actions. If you pass -a arguments, it removes only the watches you specify:

         floss$ cvs watch remove -a commit hello.c

This means that you want to stop receiving notifications about commits but continue to receive notifications about edits and unedits (assuming you were watching edits and unedits to begin with, that is).

There are two special actions you can pass to the -a flag: all or none. The former means all actions that are eligible for watching (edits, commits, and unedits, as of this writing), and the latter means none of these. Because CVS's default behavior, in the absence of -a, is to watch all actions, and because watching none is the same as removing yourself from the watch list entirely, it's hard to imagine a situation in which it would be useful to specify either of these two special actions. However, cvs edit also takes the -a option, and in this case, it can be useful to specify all or none. For example, someone working on a file very briefly may not want to receive any notifications about what other people do with the file. Thus, this command

         paste$ whoami
         qsmith
         paste$ cvs edit -a none README.txt

causes watchers of README.txt to be notified that qsmith is about to work on it, but qsmith would not be added as a temporary watcher of README.txt during his editing session (which he normally would have been), because he asked not to watch any actions.

Remember that you can only affect your own watches with the cvs watch command. You may stop watching a certain file yourself, but that won't change anyone else's watches.

Node: Finding Out Who Is Watching What, Next: Reminding People To Use Watches, Previous: Controlling What Actions Are Watched, Up: Watches (CVS As Telephone)

### Finding Out Who Is Watching What

Sometimes you may want to know who's watching before you even run cvs edit or want to see who is editing what without adding yourself to any watch lists. Or you may have forgotten exactly what your own status is. After setting and unsetting a few watches and committing some files, it's easy to lose track of what you're watching and editing.

CVS provides two commands to show who's watching and who's editing files - cvs watchers and cvs editors:

         floss$ whoami
         jrandom
         floss$ cvs watch add hello.c
         floss$ cvs watchers hello.c
         hello.c jrandom  edit unedit  commit
         floss$ cvs watch remove -a unedit hello.c
         floss$ cvs watchers hello.c
         hello.c jrandom  edit commit
         floss$ cvs watch add README.txt
         floss$ cvs watchers
         README.txt      jrandom edit    unedit  commit
         hello.c jrandom edit    commit
         floss$

Notice that the last cvs watchers command doesn't specify any files and, therefore, shows watchers for all files (all those that have watchers, that is).

All of the watch and edit commands have this behavior in common with other CVS commands. If you specify file names, they act on those files. If you specify directory names, they act on everything in that directory and its subdirectories. If you don't specify anything, they act on the current directory and everything underneath it, to as many levels of depth as are available. For example (continuing with the same session):

         floss$ cvs watch add a-subdir/whatever.c
         floss$ cvs watchers
         README.txt      jrandom edit    unedit  commit
         hello.c jrandom edit    commit
         a-subdir/whatever.c     jrandom edit    unedit  commit
         floss$ cvs watch add
         floss$ cvs watchers
         README.txt      jrandom edit    unedit  commit
         foo.gif jrandom edit    unedit  commit
         hello.c jrandom edit    commit  unedit
         a-subdir/whatever.c     jrandom edit    unedit  commit
         a-subdir/subsubdir/fish.c       jrandom edit    unedit  commit
         b-subdir/random.c       jrandom edit    unedit  commit
         floss$

The last two commands made jrandom a watcher of every file in the project and then showed the watch list for every file in the project, respectively. The output of `cvs watchers` doesn't always line up perfectly in columns because it mixes tab stops with information of varying length, but the lines are consistently formatted:

         [FILENAME] [whitespace] WATCHER [whitespace] ACTIONS-BEING-WATCHED...

Now watch what happens when qsmith starts to edit one of the files:

         paste$ cvs edit hello.c
         paste$ cvs watchers
         README.txt      jrandom edit    unedit  commit
         foo.gif jrandom edit    unedit  commit
         hello.c jrandom edit    commit  unedit
                qsmith  tedit   tunedit tcommit
         a-subdir/whatever.c     jrandom edit    unedit  commit
         a-subdir/subsubdir/fish.c       jrandom edit    unedit  commit
         b-subdir/random.c       jrandom edit    unedit  commit

The file hello.c has acquired another watcher: qsmith himself (note that the file name is not repeated but is left as white space at the beginning of the line - this would be important if you ever wanted to write a program that parses watchers output). Because he's editing hello.c, qsmith has a temporary watch on the file; it goes away as soon as he commits a new revision of hello.c. The prefix `t` in front of each of the actions indicates that these are temporary watches. If qsmith adds himself as a regular watcher of hello.c as well

         paste$ cvs watch add hello.c
         README.txt      jrandom edit    unedit  commit
         foo.gif jrandom edit    unedit  commit
         hello.c jrandom edit    commit  unedit
                qsmith  tedit   tunedit tcommit edit    unedit  commit
         a-subdir/whatever.c     jrandom edit    unedit  commit
         a-subdir/subsubdir/fish.c       jrandom edit    unedit  commit
         b-subdir/random.c       jrandom edit    unedit  commit

he is listed as both a temporary watcher and a permanent watcher. You may think that the permanent watch status would simply override the temporary, so that the line would look like this:

                 qsmith  edit    unedit  commit

However, CVS can't just replace the temporary watches because it doesn't know in what order things happen. Will qsmith remove himself from the permanent watch list before ending his editing session, or will he finish the edits while still remaining a watcher? If the former, the edit/unedit/commit actions disappear while the tedit/tunedit/tcommit ones remain; if the latter, the reverse would happen.

Anyway, that side of the watch list is usually not of great concern. Most of the time, what you want to do is run

         floss$ cvs watchers

or

         floss$ cvs editors

from the top level of a project and see who's doing what. You don't really need to know the details of who cares about what actions: the important things are people and files.

Node: Reminding People To Use Watches, Next: What Watches Look Like In The Repository, Previous: Finding Out Who Is Watching What, Up: Watches (CVS As Telephone)

### Reminding People To Use Watches

You've probably noticed that the watch features are utterly dependent on the cooperation of all the developers. If someone just starts editing a file without first running cvs edit, no one else will know about it until the changes get committed. Because cvs edit is an additional step, not part of the normal development routine, people can easily forget to do it.

Although CVS can't force someone to use cvs edit, it does have a mechanism for reminding people to do so - the watch on command:

         floss$ cvs -q co myproj
         U myproj/README.txt
         U myproj/foo.gif
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         floss$ cd myproj
         floss$ cvs watch on hello.c
         floss$

By running cvs watch on hello.c, jrandom causes future checkouts of myproj to create hello.c read-only in the working copy. When qsmith tries to work on it, he'll discover that it's read-only and be reminded to run cvs edit first:

         paste$ cvs -q co myproj
         U myproj/README.txt
         U myproj/foo.gif
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         paste$ cd myproj
         paste$ ls -l
         total 6
         drwxr-xr-x   2 qsmith    users        1024 Jul 19 01:06 CVS/
         -rw-r--r--   1 qsmith    users          38 Jul 12 11:28 README.txt
         drwxr-xr-x   4 qsmith    users        1024 Jul 19 01:06 a-subdir/
         drwxr-xr-x   3 qsmith    users        1024 Jul 19 01:06 b-subdir/
         -rw-r--r--   1 qsmith    users         673 Jun 20 22:47 foo.gif
         -r--r--r--   1 qsmith    users         188 Jul 18 01:20 hello.c
         paste$

When he does so, the file becomes read-write. He can then edit it, and when he commits, it becomes read-only again:

         paste$ cvs edit hello.c
         paste$ ls -l hello.c
         -rw-r--r--   1 qsmith    users         188 Jul 18 01:20 hello.c
         paste$ emacs hello.c
           ...
         paste$ cvs commit -m "say hello in Aramaic" hello.c
         Checking in hello.c;
         /usr/local/newrepos/myproj/hello.c,v  <--  hello.c
         new revision: 1.12; previous revision: 1.11
         done
         paste$ ls -l hello.c
         -r--r--r--   1 qsmith    users         210 Jul 19 01:12 hello.c
         paste$

His edit and commit will send notification to all watchers of hello.c. Note that jrandom isn't necessarily one of them. By running cvs watch on hello.c, jrandom did not add herself to the watch list for that file; she merely specified that it should be checked out read-only. People who want to watch a file must remember to add themselves to its watch list - CVS cannot help them with that.

Turning on watches for a single file may be the exception. Generally, it's more common to turn on watches project-wide:

         floss$ cvs -q co myproj
         U myproj/README.txt
         U myproj/foo.gif
         U myproj/hello.c
         U myproj/a-subdir/whatever.c
         U myproj/a-subdir/subsubdir/fish.c
         U myproj/b-subdir/random.c
         floss$ cd myproj
         floss$ cvs watch on
         floss$

This action amounts to announcing a policy decision for the entire project: "Please use cvs edit to tell watchers what you're working on, and feel free to watch any file you're interested in or responsible for." Every file in the project will be checked out read-only, and thus people will be reminded that they're expected to use cvs edit before working on anything.

Curiously, although checkouts of watched files make them read-only, updates do not. If qsmith had checked out his working copy before jrandom ran cvs watch on, his files would have stayed read-write, remaining so even after updates. However, any file he commits after jrandom turns watching on will become read-only. If jrandom turns off watches

         floss$ cvs watch off

qsmith's read-only files do not magically become read-write. On the other hand, after he commits one, it will not revert to read-only again (as it would have if watches were still on).

It's worth noting that qsmith could, were he truly devious, make files in his working copy writeable by using the standard Unix `chmod` command, bypassing `cvs edit` entirely

         paste$ chmod u+w hello.c

or if he wanted to get everything in one fell swoop:

         paste$ chmod -R u+w .

There is nothing CVS can do about this. Working copies by their nature are private sandboxes - the watch features can open them up to public scrutiny a little bit, but only as far as the developer permits. Only when a developer does something that affects the repository (such as commits) is her privacy unconditionally lost.

The relationship among watch add, watch remove, watch on, and watch off probably seems a bit confusing. It may help to summarize the overall scheme: `add` and `remove` are about adding or removing users from a file's watch list; they don't have anything to do with whether files are read-only on checkout or after commits. `on` and `off` are only about file permissions. They don't have anything to do with who is on a file's watch list; rather, they are tools to help remind developers of the watch policy by causing working-copy files to become read-only.

All of this may seem a little inconsistent. In a sense, using watches works against the grain of CVS. It deviates from the idealized universe of multiple developers editing freely in their working copies, hidden from each other until they choose to commit. With watches, CVS gives developers convenient shortcuts for informing each other of what's going on in their working copies; however, it has no way to enforce observation policies, nor does it have a definitive concept of what constitutes an editing session. Nevertheless, watches can be helpful in certain circumstances if developers work with them.

Node: What Watches Look Like In The Repository, Previous: Reminding People To Use Watches, Up: Watches (CVS As Telephone)

### What Watches Look Like In The Repository

In the interests of stamping out black boxes and needless mystery, let's take a quick look at how watches are implemented in the repository. We'll only take a quick look, though, because it's not pretty.

When you set a watch

         floss$ pwd
         /home/jrandom/myproj
         floss$ cvs watch add hello.c
         floss$ cvs watchers
         hello.c jrandom edit    unedit  commit
         floss$

CVS records it in the special file, `CVS/fileattr`, in the appropriate repository subdirectory:

         floss$ cd /usr/local/newrepos
         floss$ ls
         CVSROOT/   myproj/
         floss$ cd myproj
         floss$ ls
         CVS/          a-subdir/     foo.gif,v
         README.txt,v  b-subdir/     hello.c,v
         floss$ cd CVS
         floss$ ls
         fileattr
         floss$ cat fileattr
         Fhello.c        _watchers=jrandom>edit+unedit+commit
         floss$

The fact that fileattr is stored in a CVS subdirectory in the repository does not mean that the repository has become a working copy. It's simply that the name `CVS` was already reserved for bookkeeping in the working copy, so CVS can be sure no project will ever need a subdirectory of that name in the repository.

I won't describe the format of `fileattr` formally; you can probably grok it pretty well just by watching it change from command to command:

         floss$ cvs watch add hello.c
         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         Fhello.c        _watchers=jrandom>edit+unedit+commit
         floss$ cvs watch add README.txt
         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         Fhello.c        _watchers=jrandom>edit+unedit+commit
         FREADME.txt     _watchers=jrandom>edit+unedit+commit
         floss$ cvs watch on hello.c
         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         Fhello.c        _watchers=jrandom>edit+unedit+commit;_watched=
         FREADME.txt     _watchers=jrandom>edit+unedit+commit
         floss$ cvs watch remove hello.c
         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         Fhello.c        _watched=
         FREADME.txt     _watchers=jrandom>edit+unedit+commit
         floss$ cvs watch off hello.c
         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         FREADME.txt     _watchers=jrandom>edit+unedit+commit
         floss$

Edit records are stored in fileattr, too. Here's what happens when qsmith adds himself as an editor:

         paste$ cvs edit hello.c

         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         Fhello.c        _watched=;_editors=qsmith>Tue Jul 20 04:53:23 1999 GMT+floss\
         +/home/qsmith/myproj;_watchers=qsmith>tedit+tunedit+tcommit
         FREADME.txt     _watchers=jrandom>edit+unedit+commit

Finally, note that CVS removes fileattr and the CVS subdirectory when there are no more watchers or editors for any of the files in that directory:

         paste$ cvs unedit

         floss$ cvs watch off
         floss$ cvs watch remove
         floss$ cat /usr/local/newrepos/myproj/CVS/fileattr
         cat: /usr/local/newrepos/myproj/CVS/fileattr: No such file or directory
         floss$

It should be clear after this brief exposure that the details of parsing fileattr format are better left to CVS. The main reason to have a basic understanding of the format - aside from the inherent satisfaction of knowing what's going on behind the curtain - is if you try to write an extension to the CVS watch features or debug some problem in them. It's sufficient to know that you shouldn't be alarmed if you see CVS/ subdirectories popping up in your repository. They're the only safe place CVS has to store meta-information such as watch lists.

Node: Log Messages And Commit Emails, Next: Changing A Log Message After Commit, Previous: Watches (CVS As Telephone), Up: Advanced CVS

### Log Messages And Commit Emails

Commit emails are notices sent out at commit time, showing the log message and files involved in the commit. They usually go to all project participants and sometimes to other interested parties. The details of setting up commit emails were covered in Repository Administration, so I won't repeat them here. I have noticed, however, that commit emails can sometimes result in unexpected side effects to projects, effects that you may want to take into account if you set up commit emails for your project.

First, be prepared for the messages to be mostly ignored. Whether people read them depends, at least partly, on the frequency of commits in your project. Do developers tend to commit one big change at the end of the day, or many small changes throughout the day? The closer your project is to the latter, the thicker the barrage of tiny commit notices raining down on the developers all day long, and the less inclined they will be to pay attention to each message.

This doesn't mean the notices aren't useful, just that you shouldn't count on every person reading every message. It's still a convenient way for people to keep tabs on who's doing what (without the intrusiveness of watches). When the emails go to a publicly subscribable mailing list, they are a wonderful mechanism for giving interested users (and future developers!) a chance to see what happens in the code on a daily basis.

You may want to consider having a designated developer who watches all log messages and has an overview of activity across the entire project (of course, a good project leader will probably be doing this anyway). If there are clear divisions of responsibility - say, certain developers are "in charge of" certain subdirectories of the project - you could do some fancy scripting in CVSROOT/loginfo to see that each responsible party receives specially marked notices of changes made in their area. This will help ensure that the developers will at least read the email that pertains to their subdirectories.

A more interesting side effect happens when commit emails aren't ignored. People start to use them as a realtime communications method. Here's the kind of log message that can result:

         Finished feedback form; fixed the fonts and background colors on the
         home page.  Whew!  Anyone want to go to Mon Lung for lunch?

There's nothing wrong with this, and it makes the logs more fun to read over later. However, people need to be aware that log messages, such as the following, are not only distributed by email but is also preserved forever in the project's history. For example, griping about customer specifications is a frequent pastime among programmers; it's not hard to imagine someone committing a log message like this one, knowing that the other programmers will soon see it in their email:

         Truncate four-digit years to two-digits in input.  What the customer
         wants, the customer gets, no matter how silly & wrong.  Sigh.

This makes for an amusing email, but what happens if the customer reviews the logs someday? (I'll bet similar concerns have led more than one site to set up CVSROOT/loginfo so that it invokes scripts to guard against offensive words in log messages!)

The overall effect of commit emails seems to be that people become less willing to write short or obscure log messages, which is probably a good thing. However, they may need to be reminded that their audience is anyone who might ever read the logs, not just the people receiving commit emails.

Node: Changing A Log Message After Commit, Next: Getting Rid Of A Working Copy, Previous: Log Messages And Commit Emails, Up: Advanced CVS

### Changing A Log Message After Commit

Just in case someone does commit a regrettable log message, CVS enables you to rewrite logs after they've been committed. It's done with the -m option to the admin command (this command is covered in more detail later in this chapter) and allows you to change one log message (per revision, per file) at a time. Here's how it works:

         floss$ cvs admin -m 1.7:"Truncate four-digit years to two in input." date.c
         RCS file: /usr/local/newrepos/someproj/date.c,v
         done
         floss$

The original, offensive log message that was committed with revision 1.7 has been replaced with a perfectly innocent - albeit duller - message. Don't forget the colon separating the revision number from the new log message.

If the new log message consists of multiple lines, put it in a file and do this:

         floss$ cvs admin -m 1.7:"`cat new-log-message.txt`" date.c

(This example was sent in by Peter Ross <peter.ross@miscrit.be>; note that it only works for Unix users.)

If the bad message was committed into multiple files, you'll have to run cvs admin separately for each one, because the revision number is different for each file. Therefore, this is one of the few commands in CVS that requires you to pass a single file name as argument:

         floss$ cvs admin -m 1.2:"very boring log message" hello.c README.txt foo.gif
         cvs admin: while processing more than one file:
         cvs [admin aborted]: attempt to specify a numeric revision
         floss$

Confusingly, you get the same error if you pass no file names (because CVS then assumes all the files in the current directory and below are implied arguments):

         floss$ cvs admin -m 1.2:"very boring log message"
         cvs admin: while processing more than one file:
         cvs [admin aborted]: attempt to specify a numeric revision
         floss$

(As is unfortunately often the case with CVS error messages, you have to see things from CVS's point of view before the message makes sense!)

Invoking `admin -m` actually changes the project's history, so use it with care. There will be no record that the log message was ever changed - it will simply appear as if that revision had been originally committed with the new log message. No trace of the old message will be left anywhere (unless you saved the original commit email).

Although its name might seem to imply that only the designated CVS administrator can use it, in fact anyone can run `cvs admin`, as long as they have write access to the project in question. Nevertheless, it is best used with caution; the ability to change log messages is mild compared with other potentially damaging things it can do. See CVS Reference for more about `admin`, as well as a way to restrict its use.

Node: Getting Rid Of A Working Copy, Next: History -- A Summary Of Repository Activity, Previous: Changing A Log Message After Commit, Up: Advanced CVS

### Getting Rid Of A Working Copy

In typical CVS usage, the way to get rid of a working copy directory tree is to remove it like any other directory tree:

         paste$ rm -rf myproj

However, if you eliminate your working copy this way, other developers will not know that you have stopped using it. CVS provides a command to relinquish a working copy explicitly. Think of release as the opposite of checkout - you're telling the repository that you're done with the working copy now. Like checkout, release is invoked from the parent directory of the tree:

         paste$ pwd
         /home/qsmith/myproj
         paste$ cd ..
         paste$ ls
         myproj
         paste$ cvs release myproj
         You have [0] altered files in this repository.
         Are you sure you want to release directory 'myproj': y
         paste$

If there are any uncommitted changes in the repository, the release fails, meaning that it just lists the modified files and otherwise has no effect. Assuming the tree is clean (totally up to date), release records in the repository that the working copy has been released.

You can also have release automatically delete the working tree for you, by passing the -d flag:

         paste$ ls
         myproj
         paste$ cvs release -d myproj
         You have [0] altered files in this repository.
         Are you sure you want to release (and delete) directory 'myproj: y
         paste$ ls
         paste$

As of CVS version 1.10.6, the release command is not able to deduce the repository's location by examining the working copy (this is because release is invoked from above the working copy, not within it). You must pass the `-d <REPOS>` global option or make sure that your CVSROOT environment variable is set correctly. (This bug may be fixed in future versions of CVS.)

The Cederqvist claims that if you use release instead of just deleting the working tree, people with watches set on the released files will be notified just as if you had run `unedit`. However, I tried to verify this experimentally, and it does not seem to be true.

Node: History -- A Summary Of Repository Activity, Next: Annotations -- A Detailed View Of Project Activity, Previous: Getting Rid Of A Working Copy, Up: Advanced CVS

### History - A Summary Of Repository Activity

In Repository Administration, I briefly mentioned the cvs history command. This command displays a summary of all checkouts, commits, updates, rtags, and releases done in the repository (at least, since logging was enabled by the creation of the CVSROOT/history file in the repository). You can control the format and contents of the summary with various options.

The first step is to make sure that logging is enabled in your repository. The repository administrator should first make sure there is a history file

         floss$ cd /usr/local/newrepos/CVSROOT
         floss$ ls -l history
         ls: history: No such file or directory
         floss$

and if there isn't one, create it, as follows:

         floss$ touch history
         floss$ ls -l history
         -rw-r--r--   1 jrandom   cvs           0 Jul 22 14:57 history
         floss$

This history file also needs to be writeable by everyone who uses the repository, otherwise they'll get an error every time they try to run a CVS command that modifies that file. The easiest way is simply to make the file world-writeable:

         floss$ chmod a+rw history
         floss$ ls -l history
         -rw-rw-rw-   1 jrandom   cvs           0 Jul 22 14:57 history
         floss$

If the repository was created with the `cvs init` command, the history file already exists. You may still have to fix its permissions, however.

The rest of these examples assume that history logging has been enabled for a while, so that data has had time to accumulate in the history file.

The output of cvs history is somewhat terse (it's probably intended to be parsed by programs rather than humans, although it is readable with a little study). Let's run it once and see what we get:

         paste$ pwd
         /home/qsmith/myproj
         paste$ cvs history -e -a
         O 07/25 15:14 +0000 qsmith  myproj =mp=     ~/*
         M 07/25 15:16 +0000 qsmith  1.14 hello.c    myproj == ~/mp
         U 07/25 15:21 +0000 qsmith  1.14 README.txt myproj == ~/mp
         G 07/25 15:21 +0000 qsmith  1.15 hello.c    myproj == ~/mp
         A 07/25 15:22 +0000 qsmith  1.1  goodbye.c  myproj == ~/mp
         M 07/25 15:23 +0000 qsmith  1.16 hello.c    myproj == ~/mp
         M 07/25 15:26 +0000 qsmith  1.17 hello.c    myproj == ~/mp
         U 07/25 15:29 +0000 qsmith  1.2  goodbye.c  myproj == ~/mp
         G 07/25 15:29 +0000 qsmith  1.18 hello.c    myproj == ~/mp
         M 07/25 15:30 +0000 qsmith  1.19 hello.c    myproj == ~/mp
         O 07/23 03:45 +0000 jrandom myproj =myproj= ~/src/*
         F 07/23 03:48 +0000 jrandom        =myproj= ~/src/*
         F 07/23 04:06 +0000 jrandom        =myproj= ~/src/*
         M 07/25 15:12 +0000 jrandom 1.13 README.txt myproj == ~/src/myproj
         U 07/25 15:17 +0000 jrandom 1.14 hello.c    myproj == ~/src/myproj
         M 07/25 15:18 +0000 jrandom 1.14 README.txt myproj == ~/src/myproj
         M 07/25 15:18 +0000 jrandom 1.15 hello.c    myproj == ~/src/myproj
         U 07/25 15:23 +0000 jrandom 1.1  goodbye.c  myproj == ~/src/myproj
         U 07/25 15:23 +0000 jrandom 1.16 hello.c    myproj == ~/src/myproj
         U 07/25 15:26 +0000 jrandom 1.1  goodbye.c  myproj == ~/src/myproj
         G 07/25 15:26 +0000 jrandom 1.17 hello.c    myproj == ~/src/myproj
         M 07/25 15:27 +0000 jrandom 1.18 hello.c    myproj == ~/src/myproj
         C 07/25 15:30 +0000 jrandom 1.19 hello.c    myproj == ~/src/myproj
         M 07/25 15:31 +0000 jrandom 1.20 hello.c    myproj == ~/src/myproj
         M 07/25 16:29 +0000 jrandom 1.3  whatever.c myproj/a-subdir == ~/src/myproj
         paste$

There, isn't that clear?

Before we examine the output, notice that the invocation included two options: -e and -a. When you run history, you almost always want to pass options telling it what data to report and how to report it. In this respect, it differs from most other CVS commands, which usually do something useful when invoked without any options. In this example, the two flags meant "everything" (show every kind of event that happened) and "all" (for all users), respectively.

Another way that history differs from other commands is that, although it is usually invoked from within a working copy, it does not restrict its output to that working copy's project. Instead, it shows all history events from all projects in the repository - the working copy merely serves to tell CVS from which repository to retrieve the history data. (In the preceding example, the only history data in that repository is for the `myproj` project, so that's all we see.)

The general format of the output is:

         CODE DATE USER [REVISION] [FILE] PATH_IN_REPOSITORY ACTUAL_WORKING_COPY_NAME

The code letters refer to various CVS operations, as shown in Table 6.1.

For operations (such as checkout) that are about the project as a whole rather than about individual files, the revision and file are omitted, and the repository path is placed between the equal signs.

Although the output of the history command was designed to be compact, parseable input for other programs, CVS still gives you a lot of control over its scope and content. The options shown in Table 6.2 control what types of events get reported.

         Table 6.1  The meaning of the code letters.

         Letter	        Meaning
         ======          =========================================================
         O		Checkout
         T		Tag
         F		Release
         W		Update (no user file, remove from entries file)
         U		Update (file overwrote unmodified user file)
         G		Update (file was merged successfully into modified user file)
         C		Update (file was merged, but conflicts w/ modified user file)
         M		Commit (from modified file)
         A		Commit (an added file)
         R		Commit (the removal of a file)
         E		Export

         Table 6.2  Options to filter by event type.

         Option	        Meaning
         ==========      =========================================================
         -m MODULE	Show historical events affecting MODULE.
         -c		Show commit events.
         -o		Show checkout events.
         -T		Show tag events.
         -x CODE(S)	Show all events of type CODE (one or more of OTFWUGCMARE).
         -e		Show all types of events, period.  Once you have
                         selected what type of events you want reported, you can
                         filter further with the options shown in Table 6.3.

         Table 6.3  Options to filter by user.

         Option	        Meaning
         ==========      =========================================================
         -a		Show actions taken by all users
         -w		Show only actions taken from within this working copy
         -l		Show only the last time this user took the action
         -u USER 	Show records for USER

Node: Annotations -- A Detailed View Of Project Activity, Next: Annotations And Branches, Previous: History -- A Summary Of Repository Activity, Up: Advanced CVS

### Annotations - A Detailed View Of Project Activity

### The annotate Command

If the history command gives an overview of project activity, the annotate command is a way of attaching a zoom lens to the view. With `annotate`, you can see who was the last person to touch each line of a file, and at what revision they touched it:

         floss$ cvs annotate
         Annotations for README.txt
         ***************
         1.14         (jrandom  25-Jul-99): blah
         1.13         (jrandom  25-Jul-99): test 3 for history
         1.12         (qsmith   19-Jul-99): test 2
         1.11         (qsmith   19-Jul-99): test
         1.10         (jrandom  12-Jul-99): blah
         1.1          (jrandom  20-Jun-99): Just a test project.
         1.4          (jrandom  21-Jun-99): yeah.
         1.5          (jrandom  21-Jun-99): nope.
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.15         (jrandom  25-Jul-99):   /* another test for history */
         1.13         (qsmith   19-Jul-99):   /* random change number two */
         1.10         (jrandom  12-Jul-99):   /* test */
         1.21         (jrandom  25-Jul-99):   printf ("Hellooo, world!\n");
         1.3          (jrandom  21-Jun-99):   printf ("hmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.11         (qsmith   18-Jul-99):   /* added this comment */
         1.16         (qsmith   25-Jul-99):   /* will merge these changes */
         1.18         (jrandom  25-Jul-99):   /* will merge these changes too */
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         Annotations for a-subdir/whatever.c
         ***************
         1.3          (jrandom  25-Jul-99): /* A completely non-empty C file. */
         Annotations for a-subdir/subsubdir/fish.c
         ***************
         1.2          (jrandom  25-Jul-99): /* An almost completely empty C file. */
         Annotations for b-subdir/random.c
         ***************
         1.1          (jrandom  20-Jun-99): /* A completely empty C file. */
         floss$

The output of annotate is pretty intuitive. On the left are the revision number, developer, and date on which the line in question was added or last modified. On the right is the line itself, as of the current revision. Because every line is annotated, you can actually see the entire contents of the file, pushed over to the right by the annotation information.

If you specify a revision number or tag, the annotations are given as of that revision, meaning that it shows the most recent modification to each line at or before that revision. This is probably the most common way to use annotations - examining a particular revision of a single file to determine which developers were active in which parts of the file.

For example, in the output of the previous example, you can see that the most recent revision of hello.c is 1.21, in which jrandom did something to the line:

         printf ("Hellooo, world!\n");

One way to find out what she did is to diff that revision against the previous one:

         floss$ cvs diff -r 1.20 -r 1.21 hello.c
         Index: hello.c
         ===================================================================
         RCS file: /usr/local/newrepos/myproj/hello.c,v
         retrieving revision 1.20
         retrieving revision 1.21
         diff -r1.20 -r1.21
         9c9
         <   printf ("Hello, world!\n");
         --
         >   printf ("Hellooo, world!\n");
         floss$

Another way to find out, while still retaining a file-wide view of everyone's activity, is to compare the current annotations with the annotations from a previous revision:

         floss$ cvs annotate -r 1.20 hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.15         (jrandom  25-Jul-99):   /* another test for history */
         1.13         (qsmith   19-Jul-99):   /* random change number two */
         1.10         (jrandom  12-Jul-99):   /* test */
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.3          (jrandom  21-Jun-99):   printf ("hmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.11         (qsmith   18-Jul-99):   /* added this comment */
         1.16         (qsmith   25-Jul-99):   /* will merge these changes */
         1.18         (jrandom  25-Jul-99):   /* will merge these changes too */
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$

Although the diff reveals the textual facts of the change more concisely, the annotation may be preferable because it places them in their historical context by showing how long the previous incarnation of the line had been present (in this case, all the way since revision 1.1). That knowledge can help you decide whether to look at the logs to find out the motivation for the change:

         floss$ cvs log -r 1.21 hello.c
         RCS file: /usr/local/newrepos/myproj/hello.c,v
         Working file: hello.c
         head: 1.21
         branch:
         locks: strict
         access list:
         symbolic names:
                random-tag: 1.20
                start: 1.1.1.1
                jrandom: 1.1.1
         keyword substitution: kv
         total revisions: 22;    selected revisions: 1
         description:
         ----------------------------
         revision 1.21
         date: 1999/07/25 20:17:42;  author: jrandom;  state: Exp;  lines: +1 -1
         say hello with renewed enthusiasm
         ============================================================================
         floss$

In addition to -r, you can also filter annotations using the -D DATE option:

         floss$ cvs annotate -D "5 weeks ago" hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$ cvs annotate -D "3 weeks ago" hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.3          (jrandom  21-Jun-99):   printf ("hmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$

Node: Annotations And Branches, Next: Using Keyword Expansion, Previous: Annotations -- A Detailed View Of Project Activity, Up: Advanced CVS

### Annotations And Branches

By default, annotation always shows activity on the main trunk of development. Even when invoked from a branch working copy, it shows annotations for the trunk unless you specify otherwise. (This tendency to favor the trunk is either a bug or a feature, depending on your point of view.) You can force CVS to annotate a branch by passing the branch tag as an argument to -r. Here is an example from a working copy in which hello.c is on a branch named `Brancho_Gratuito`, with at least one change committed on that branch:

         floss$ cvs status hello.c
         ===================================================================
         File: hello.c           Status: Up-to-date

           Working revision:    1.10.2.2        Sun Jul 25 21:29:05 1999
           Repository revision: 1.10.2.2        /usr/local/newrepos/myproj/hello.c,v
           Sticky Tag:          Brancho_Gratuito (branch: 1.10.2)
           Sticky Date:         (none)
           Sticky Options:      (none)

         floss$ cvs annotate hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.10         (jrandom  12-Jul-99):   /* test */
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.3          (jrandom  21-Jun-99):   printf ("hmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$ cvs annotate -r Brancho_Gratuito hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.10         (jrandom  12-Jul-99):   /* test */
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.10.2.2     (jrandom  25-Jul-99):   printf ("hmmmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.10.2.1     (jrandom  25-Jul-99):   printf ("added this line");
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$

You can also pass the branch number itself:

         floss$ cvs annotate -r 1.10.2 hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.10         (jrandom  12-Jul-99):   /* test */
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.10.2.2     (jrandom  25-Jul-99):   printf ("hmmmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.10.2.1     (jrandom  25-Jul-99):   printf ("added this line");
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$

or a full revision number from the branch:

         floss$ cvs annotate -r 1.10.2.1 hello.c
         Annotations for hello.c
         ***************
         1.1          (jrandom  20-Jun-99): #include <stdio.h>
         1.1          (jrandom  20-Jun-99):
         1.1          (jrandom  20-Jun-99): void
         1.1          (jrandom  20-Jun-99): main ()
         1.1          (jrandom  20-Jun-99): {
         1.10         (jrandom  12-Jul-99):   /* test */
         1.1          (jrandom  20-Jun-99):   printf ("Hello, world!\n");
         1.3          (jrandom  21-Jun-99):   printf ("hmmm\n");
         1.4          (jrandom  21-Jun-99):   printf ("double hmmm\n");
         1.10.2.1     (jrandom  25-Jul-99):   printf ("added this line");
         1.2          (jrandom  21-Jun-99):   printf ("Goodbye, world!\n");
         1.1          (jrandom  20-Jun-99): }
         floss$

If you do this, remember that the numbers are only valid for that particular file. In general, it's probably better to use the branch name wherever possible.

Node: Using Keyword Expansion, Next: Going Out On A Limb (How To Work With Branches And Survive), Previous: Annotations And Branches, Up: Advanced CVS

### Using Keyword Expansion

You may recall a brief mention of `keyword expansion` in An Overview of CVS. RCS keywords are special words, surrounded by dollar signs, that CVS looks for in text files and expands into revision-control information. For example, if a file contains

         $Author$

then when updating the file to a given revision, CVS will expand it to the username of the person who committed that revision:

         $Author: jrandom $

CVS is also sensitive to keywords in their expanded form, so that once expanded, they continue to be updated as appropriate.

Although keywords don't actually offer any information that's not available by other means, they give people a convenient way to see revision control facts embedded in the text of the file itself, rather than by invoking some arcane CVS operation.

Here are a few other commonly used keywords:

         $Date$       ==>  date of last commit, expands to ==>
         $Date: 1999/07/26 06:39:46 $

         $Id$         ==>  filename, revision, date, and author; expands to ==>
         $Id: hello.c,v 1.11 1999/07/26 06:39:46 jrandom Exp $

         $Revision$   ==>  exactly what you think it is, expands to ==>
         $Revision: 1.11 $

         $Source$     ==> path to corresponding repository file, expands to ==>
         $Source: /usr/local/newrepos/tossproj/hello.c,v $

         $Log$        ==>  accumulating log messages for the file, expands to ==>
         $Log: hello.c,v $
         Revision 1.2  1999/07/26 06:47:52  jrandom
         ...and this is the second log message.

         Revision 1.1  1999/07/26 06:39:46  jrandom
         This is the first log message...

The $Log$ keyword is the only one of these that expands to cover multiple lines, so its behavior is unique. Unlike the others, it does not replace the old expansion with the new one, but instead inserts the latest expansion, plus an additional blank line, right after the keyword (thereby pushing any previous expansions downward). Furthermore, any text between the beginning of the line and $Log is used as a prefix for the expansions (this is done to ensure that the log messages stay commented in program code). For example, if you put this into the file

         // $Log$

it will expand to something like this on the first commit:

         // $Log: hello.c,v $
         // Revision 1.14  1999/07/26 07:03:20  jrandom
         // this is the first log message...
         //

this on the second:

         // $Log: hello.c,v $
         // Revision 1.15  1999/07/26 07:04:40  jrandom
         // ...and this is the second log message...
         //
         // Revision 1.14  1999/07/26 07:03:20  jrandom
         // this is the first log message...
         //

and so on:

         // $Log: hello.c,v $
         // Revision 1.16  1999/07/26 07:05:34  jrandom
         // ...and this is the third!
         //
         // Revision 1.15  1999/07/26 07:04:40  jrandom
         // ...and this is the second log message...
         //
         // Revision 1.14  1999/07/26 07:03:20  jrandom
         // this is the first log message...
         //

You may not want to keep your entire log history in the file all the time; if you do, you can always remove the older sections when it starts to get too lengthy. It's certainly more convenient than running cvs log, and it may be worthwhile in projects where people must constantly read over the logs.

A more common technique may be to include $Revision$ in a file and use it as the version number for the program. This can work if the project consists of essentially one file or undergoes frequent releases and has at least one file that is guaranteed to be modified between every release. You can even use an RCS keyword as a value in program code:

         VERSION = "$Revision: 1.114 $";

CVS expands that keyword just like any other; it has no concept of the programming language's semantics and does not assume that the double quotes protect the string in any way.

A complete list of keywords (there are a few more, rather obscure ones) is given in CVS Reference.

Node: Going Out On A Limb (How To Work With Branches And Survive), Next: Tracking Third-Party Sources (Vendor Branches), Previous: Using Keyword Expansion, Up: Advanced CVS

### Going Out On A Limb (How To Work With Branches And Survive)

Branches are simultaneously one of the most important and most easily misused features of CVS. Isolating risky or disruptive changes onto a separate line of development until they stabilize can be immensely helpful. If not properly managed, however, branches can quickly propel a project into confusion and cascading chaos, as people lose track of what changes have been merged when.

Node: Some Principles For Working With Branches, Next: Merging Repeatedly Into The Trunk, Up: Going Out On A Limb (How To Work With Branches And Survive)

### Some Principles For Working With Branches

To work successfully with branches, your development group should adhere to these principles:

- Minimize the number of branches active at any one time. The more branches under development at the same time, the more likely they are to conflict when merged into the trunk. In practical terms, the way to accomplish this is to merge as frequently as you can (whenever a branch is at a stable point) and to move development back onto the trunk as soon as feasible. By minimizing the amount of parallel development going on, everyone is better able to keep track of what's going on on each branch, and the possibility of conflicts on merge is reduced.

  This does not mean minimizing the absolute number of branches in the project, just the number being worked on at any given time.

- Minimize the complexity - that is, the depth - of your branching scheme. There are circumstances in which it's appropriate to have branches from branches, but they are very rare (you may get through your entire programming life without ever encountering one). Just because CVS makes it technically possible to have arbitrary levels of nested branching, and to merge from any branch to any other branch, doesn't mean you actually want to do these things. In most situations, it's best to have all your branches rooted at the trunk and to merge from branch to trunk and back out again.
- Use consistently named tags to mark all branch and merge events. Ideally, the meaning of each tag and its relationship to other branches and tags should be apparent from the tag name. (The point of this will become clearer as we go through the examples.)

With those principles in mind, let's take a look at a typical branch development scenario. We'll have jrandom on the trunk and qsmith on the branch, but note that there could just as well be multiple developers on the trunk and/or on the branch. Regular development along either line can involve any number of people; however, the tagging and merging are best done by one person on each side, as you'll see.

Node: Merging Repeatedly Into The Trunk, Next: The Dovetail Approach -- Merging In And Out Of The Trunk, Previous: Some Principles For Working With Branches, Up: Going Out On A Limb (How To Work With Branches And Survive)

### Merging Repeatedly Into The Trunk

Let's assume qsmith needs to do development on a branch for a while, to avoid destabilizing the trunk that he shares with jrandom. The first step is to create the branch. Notice how qsmith creates a regular (non-branch) tag at the branch point first, and then creates the branch:

         paste$ pwd
         /home/qsmith/myproj
         paste$ cvs tag Root-of-Exotic_Greetings
         cvs tag: Tagging .
         T README.txt
         T foo.gif
         T hello.c
         cvs tag: Tagging a-subdir
         T a-subdir/whatever.c
         cvs tag: Tagging a-subdir/subsubdir
         T a-subdir/subsubdir/fish.c
         cvs tag: Tagging b-subdir
         T b-subdir/random.c
         paste$ cvs tag -b Exotic_Greetings-branch
         cvs tag: Tagging .
         T README.txt
         T foo.gif
         T hello.c
         cvs tag: Tagging a-subdir
         T a-subdir/whatever.c
         cvs tag: Tagging a-subdir/subsubdir
         T a-subdir/subsubdir/fish.c
         cvs tag: Tagging b-subdir
         T b-subdir/random.c
         paste$

The point of tagging the trunk first is that it may be necessary someday to retrieve the trunk as it was the moment the branch was created. If you ever need to do that, you'll have to have a way of referring to the trunk snapshot without referring to the branch itself. Obviously, you can't use the branch tag because that would retrieve the branch, not the revisions in the trunk that form the root of the branch. The only way to do it is to make a regular tag at the same revisions the branch sprouts from. (Some people stick to this rule so faithfully that I considered listing it as "Branching Principle Number 4: Always create a non-branch tag at the branch point." However, many sites don't do it, and they generally seem to do okay, so it's really a matter of taste.) From here on, I will refer to this non-branch tag as the branch point tag.

Notice also that a naming convention is being adhered to: The branch point tag begins with `Root-of-`, then the actual branch name, which uses underscores instead of hyphens to separate words. When the actual branch is created, its tag ends with the suffix `-branch` so that you can identify it as a branch tag just by looking at the tag name. (The branch point tag `Root-of-Exotic_Greetings` does not include the -branch because it is not a branch tag.) You don't have to use this particular naming convention, of course, but you should use some convention.

Of course, I'm being extra pedantic here. In smallish projects, where everyone knows who's doing what and confusion is easy to recover from, these conventions don't have to be used. Whether you use a branch point tag or have a strict naming convention for your tags depends on the complexity of the project and the branching scheme. (Also, don't forget that you can always go back later and update old tags to use new conventions by retrieving an old tagged version, adding the new tag, and then deleting the old tag.)

Now, qsmith is ready to start working on the branch:

         paste$ cvs update -r Exotic_Greetings-branch
         cvs update: Updating .
         cvs update: Updating a-subdir
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         paste$

He makes some changes to a couple of files and commits them on the branch:

         paste$ emacs README.txt a-subdir/whatever.c b-subdir/random.c
         ...
         paste$ cvs ci -m "print greeting backwards, etc"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in README.txt;
         /usr/local/newrepos/myproj/README.txt,v  <--  README.txt
         new revision: 1.14.2.1; previous revision: 1.14
         done
         Checking in a-subdir/whatever.c;
         /usr/local/newrepos/myproj/a-subdir/whatever.c,v  <--  whatever.c
         new revision: 1.3.2.1; previous revision: 1.3
         done
         Checking in b-subdir/random.c;
         /usr/local/newrepos/myproj/b-subdir/random.c,v  <--  random.c
         new revision: 1.1.1.1.2.1; previous revision: 1.1.1.1
         done
         paste$

Meanwhile, jrandom is continuing to work on the trunk. She modifies two of the three files that qsmith touched. Just for kicks, we'll have her make changes that conflict with qsmith's work:

         floss$ emacs README.txt whatever.c
          ...
         floss$ cvs ci -m "some very stable changes indeed"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in README.txt;
         /usr/local/newrepos/myproj/README.txt,v  <--  README.txt
         new revision: 1.15; previous revision: 1.14
         done
         Checking in a-subdir/whatever.c;
         /usr/local/newrepos/myproj/a-subdir/whatever.c,v  <--  whatever.c
         new revision: 1.4; previous revision: 1.3
         done
         floss$

The conflict is not apparent yet, of course, because neither developer has tried to merge branch and trunk. Now, jrandom does the merge:

         floss$ cvs update -j Exotic_Greetings-branch
         cvs update: Updating .
         RCS file: /usr/local/newrepos/myproj/README.txt,v
         retrieving revision 1.14
         retrieving revision 1.14.2.1
         Merging differences between 1.14 and 1.14.2.1 into README.txt
         rcsmerge: warning: conflicts during merge
         cvs update: Updating a-subdir
         RCS file: /usr/local/newrepos/myproj/a-subdir/whatever.c,v
         retrieving revision 1.3
         retrieving revision 1.3.2.1
         Merging differences between 1.3 and 1.3.2.1 into whatever.c
         rcsmerge: warning: conflicts during merge
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         RCS file: /usr/local/newrepos/myproj/b-subdir/random.c,v
         retrieving revision 1.1.1.1
         retrieving revision 1.1.1.1.2.1
         Merging differences between 1.1.1.1 and 1.1.1.1.2.1 into random.c
         floss$ cvs update
         cvs update: Updating .
         C README.txt
         cvs update: Updating a-subdir
         C a-subdir/whatever.c
         cvs update: Updating a-subdir/subsubdir
         cvs update: Updating b-subdir
         M b-subdir/random.c
         floss$

Two of the files conflict. No big deal; with her usual savoir-faire, jrandom resolves the conflicts, commits, and tags the trunk as successfully merged:

         floss$ emacs README.txt a-subdir/whatever.c
          ...
         floss$ cvs ci -m "merged from Exotic_Greetings-branch (conflicts resolved)"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in README.txt;
         /usr/local/newrepos/myproj/README.txt,v  <--  README.txt
         new revision: 1.16; previous revision: 1.15
         done
         Checking in a-subdir/whatever.c;
         /usr/local/newrepos/myproj/a-subdir/whatever.c,v  <--  whatever.c
         new revision: 1.5; previous revision: 1.4
         done
         Checking in b-subdir/random.c;
         /usr/local/newrepos/myproj/b-subdir/random.c,v  <--  random.c
         new revision: 1.2; previous revision: 1.1
         done
         floss$ cvs tag merged-Exotic_Greetings
         cvs tag: Tagging .
         T README.txt
         T foo.gif
         T hello.c
         cvs tag: Tagging a-subdir
         T a-subdir/whatever.c
         cvs tag: Tagging a-subdir/subsubdir
         T a-subdir/subsubdir/fish.c
         cvs tag: Tagging b-subdir
         T b-subdir/random.c
         floss$

Meanwhile, qsmith needn't wait for the merge to finish before continuing development, as long as he makes a tag for the batch of changes from which jrandom merged (later, jrandom will need to know this tag name; in general, branches depend on frequent and thorough developer communications):

         paste$ cvs tag Exotic_Greetings-1
         cvs tag: Tagging .
         T README.txt
         T foo.gif
         T hello.c
         cvs tag: Tagging a-subdir
         T a-subdir/whatever.c
         cvs tag: Tagging a-subdir/subsubdir
         T a-subdir/subsubdir/fish.c
         cvs tag: Tagging b-subdir
         T b-subdir/random.c
         paste$ emacs a-subdir/whatever.c
          ...
         paste$ cvs ci -m "print a randomly capitalized greeting"
         cvs commit: Examining .
         cvs commit: Examining a-subdir
         cvs commit: Examining a-subdir/subsubdir
         cvs commit: Examining b-subdir
         Checking in a-subdir/whatever.c;
         /usr/local/newrepos/myproj/a-subdir/whatever.c,v  <--  whatever.c
         new revision: 1.3.2.2; previous revision: 1.3.2.1
         done
         paste$

And of course, qsmith should tag those changes once he's done:

         paste$ cvs -q tag Exotic_Greetings-2
         T README.txt
         T foo.gif
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         paste$

While all this is going on, jrandom makes a change in a different file, one that qsmith hasn't touched in his new batch of edits:

         floss$ emacs README.txt
          ...
         floss$ cvs ci -m "Mention new Exotic Greeting features" README.txt
         Checking in README.txt;
         /usr/local/newrepos/myproj/README.txt,v  <--  README.txt
         new revision: 1.17; previous revision: 1.16
         done
         floss$

At this point, qsmith has committed a new change on the branch, and jrandom has committed a nonconflicting change in a different file on the trunk. Watch what happens when jrandom tries to merge from the branch again:

         floss$ cvs -q update -j Exotic_Greetings-branch
         RCS file: /usr/local/newrepos/myproj/README.txt,v
         retrieving revision 1.14
         retrieving revision 1.14.2.1
         Merging differences between 1.14 and 1.14.2.1 into README.txt
         rcsmerge: warning: conflicts during merge
         RCS file: /usr/local/newrepos/myproj/a-subdir/whatever.c,v
         retrieving revision 1.3
         retrieving revision 1.3.2.2
         Merging differences between 1.3 and 1.3.2.2 into whatever.c
         rcsmerge: warning: conflicts during merge
         RCS file: /usr/local/newrepos/myproj/b-subdir/random.c,v
         retrieving revision 1.1
         retrieving revision 1.1.1.1.2.1
         Merging differences between 1.1 and 1.1.1.1.2.1 into random.c
         floss$ cvs -q update
         C README.txt
         C a-subdir/whatever.c
         floss$

There are conflicts! Is that what you expected?

The problem lies in the semantics of merging. Back in An Overview of CVS, I explained that when you run

         floss$ cvs update -j BRANCH

in a working copy, CVS merges into the working copy the differences between BRANCH's root and its tip. The trouble with that behavior, in this situation, is that most of those changes had already been incorporated into the trunk the first time that jrandom did a merge. When CVS tried to merge them in again (over themselves, as it were), it naturally registered a conflict.

What jrandom really wanted to do was merge into her working copy the changes between the branch's most recent merge and its current tip. You can do this by using two -j flags to update, as you may recall from An Overview of CVS, as long as you know what revision to specify with each flag. Fortunately, qsmith made a tag at exactly the last merge point (hurrah for planning ahead!), so this will be no problem. First, let's have jrandom restore her working copy to a clean state, from which she can redo the merge:

         floss$ rm README.txt a-subdir/whatever.c
         floss$ cvs -q update
         cvs update: warning: README.txt was lost
         U README.txt
         cvs update: warning: a-subdir/whatever.c was lost
         U a-subdir/whatever.c
         floss$

Now she's ready to do the merge, this time using qsmith's conveniently placed tag:

         floss$ cvs -q update -j Exotic_Greetings-1 -j Exotic_Greetings-branch
         RCS file: /usr/local/newrepos/myproj/a-subdir/whatever.c,v
         retrieving revision 1.3.2.1
         retrieving revision 1.3.2.2
         Merging differences between 1.3.2.1 and 1.3.2.2 into whatever.c
         floss$ cvs -q update
         M a-subdir/whatever.c
         floss$

Much better. The change from qsmith has been incorporated into whatever.c; jrandom can now commit and tag:

         floss$ cvs -q ci -m "merged again from Exotic_Greetings (1)"
         Checking in a-subdir/whatever.c;
         /usr/local/newrepos/myproj/a-subdir/whatever.c,v  <--  whatever.c
         new revision: 1.6; previous revision: 1.5
         done
         floss$ cvs -q tag merged-Exotic_Greetings-1
         T README.txt
         T foo.gif
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         floss$

Even if qsmith had forgotten to tag at the merge point, all hope would not be lost. If jrandom knew approximately when qsmith's first batch of changes had been committed, she could try filtering by date:

         floss$ cvs update -j Exotic_Greetings-branch:3pm -j Exotic_Greetings_branch

Although useful as a last resort, filtering by date is less than ideal because it selects the changes based on people's recollections rather than dependable developer designations. If qsmith's first mergeable set of changes had happened over several commits instead of in one commit, jrandom may mistakenly choose a date or time that would catch some of the changes, but not all of them.

There's no reason why each taggable point in qsmith's changes needs to be sent to the repository in a single commit - it just happens to have worked out that way in these examples. In real life, qsmith may make several commits between tags. He can work on the branch in isolation, as he pleases. The point of the tags is to record successive points on the branch where he considers the changes to be mergeable into the trunk. As long as jrandom always merges using two -j flags and is careful to use qsmith's merge tags in the right order and only once each, the trunk should never experience the double-merge problem. Conflicts may occur, but they will be the unavoidable kind that requires human resolution - situations in which both branch and trunk made changes to the same area of code.

Node: The Dovetail Approach -- Merging In And Out Of The Trunk, Next: The Flying Fish Approach -- A Simpler Way To Do It, Previous: Merging Repeatedly Into The Trunk, Up: Going Out On A Limb (How To Work With Branches And Survive)

### The Dovetail Approach - Merging In And Out Of The Trunk

Merging repeatedly from branch to trunk is good for the people on the trunk, because they see all of their own changes and all the changes from the branch. However, the developer on the branch never gets to incorporate any of the work being done on the trunk.

To allow that, the branch developer needs to add an extra step every now and then (meaning whenever he feels like merging in recent trunk changes and dealing with the inevitable conflicts):

         paste$ cvs update -j HEAD

The special reserved tag `HEAD` means the tip of the trunk. The preceding command merges in all of the trunk changes between the root of the current branch (`Exotic_Greetings-branch`) and the current highest revisions of each file on the trunk. Of course, qsmith should tag again after doing this, so that the trunk developers can avoid accidentally merging in their own changes when they're trying to get qsmith's.

The branch developer can likewise use the trunk's merge tags as boundaries, allowing the branch to merge exactly those trunk changes between the last merge and the trunk's current state (the same way the trunk does merges). For example, supposing jrandom had made some changes to hello.c after merging from the branch:

         floss$ emacs hello.c
          ...
         floss$ cvs ci -m "clarify algorithm" hello.c
         Checking in hello.c;
         /usr/local/newrepos/myproj/hello.c,v  <--  hello.c
         new revision: 1.22; previous revision: 1.21
         done
         floss$

Then, qsmith can merge those changes into his branch, commit, and, of course, tag:

         paste$ cvs -q update -j merged-Exotic_Greetings-1 -j HEAD
         RCS file: /usr/local/newrepos/myproj/hello.c,v
         retrieving revision 1.21
         retrieving revision 1.22
         Merging differences between 1.21 and 1.22 into hello.c
         paste$ cvs -q update
         M hello.c
         paste$ cvs -q ci -m "merged trunk, from merged-Exotic_Greetings-1 to HEAD"
         Checking in hello.c;
         /usr/local/newrepos/myproj/hello.c,v  <--  hello.c
         new revision: 1.21.2.1; previous revision: 1.21
         done
         paste$ cvs -q tag merged-merged-Exotic_Greetings-1
         T README.txt
         T foo.gif
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         paste$

Notice that jrandom did not bother to tag after committing the changes to hello.c, but qsmith did. The principle at work here is that although you don't need to tag after every little change, you should always tag after a merge or after committing your line of development up to a mergeable state. That way, other people - perhaps on other branches - have a reference point against which to base their own merges.

Node: The Flying Fish Approach -- A Simpler Way To Do It, Next: Branches And Keyword Expansion -- Natural Enemies, Previous: The Dovetail Approach -- Merging In And Out Of The Trunk, Up: Going Out On A Limb (How To Work With Branches And Survive)

### The Flying Fish Approach - A Simpler Way To Do It

There is a simpler, albeit slightly limiting, variant of the preceding. In it, the branch developers freeze while the trunk merges, and then the trunk developers create an entirely new branch, which replaces the old one. The branch developers move onto that branch and continue working. The cycle continues until there is no more need for branch development. It goes something like this (in shorthand - we'll assume jrandom@floss has the trunk and qsmith@paste has the branch, as usual):

         floss$ cvs tag -b BRANCH-1
         paste$ cvs checkout -r BRANCH-1 myproj

Trunk and branch both start working; eventually, the developers confer and decide it's time to merge the branch into the trunk:

         paste$ cvs ci -m "committing all uncommitted changes"
         floss$ cvs update -j BRANCH-1

All the changes from the branch merge in; the branch developers stop working while the trunk developers resolve any conflicts, commit, tag, and create a new branch:

         floss$ cvs ci -m "merged from BRANCH-1"
         floss$ cvs tag merged-from-BRANCH-1
         floss$ cvs tag -b BRANCH-2

Now the branch developers switch their working copies over to the new branch; they know they won't lose any uncommitted changes by doing so, because they were up-to-date when the merge happened, and the new branch is coming out of a trunk that has incorporated the changes from the old branch:

         paste$ cvs update -r BRANCH-2

And the cycle continues in that way, indefinitely; just substitute BRANCH-2 for BRANCH-1 and BRANCH-3 for BRANCH-2.

I call this the Flying Fish technique, because the branch is constantly emerging from the trunk, traveling a short distance, then rejoining it. The advantages of this approach are that it's simple (the trunk always merges in all the changes from a given branch) and the branch developers never need to resolve conflicts (they're simply handed a new, clean branch on which to work each time). The disadvantage, of course, is that the branch people must sit idle while the trunk is undergoing merge (which can take an arbitrary amount of time, depending on how many conflicts need to be resolved). Another minor disadvantage is that it results in many little, unused branches laying around instead of many unused non-branch tags. However, if having millions of tiny, obsolete branches doesn't bother you, and you anticipate fairly trouble-free merges, Flying Fish may be the easiest way to go in terms of mental bookkeeping.

Whichever way you do it, you should try to keep the separations as short as possible. If the branch and the trunk go too long without merging, they could easily begin to suffer not just from textual drift, but semantic drift as well. Changes that conflict textually are the easiest ones to resolve. Changes that conflict conceptually, but not textually, often prove hardest to find and fix. The isolation of a branch, so freeing to the developers, is dangerous precisely because it shields each side from the effects of others' changes...for a time. When you use branches, communication becomes more vital than ever: Everyone needs to make extra sure to review each others' plans and code to ensure that they're all staying on the same track.

Node: Branches And Keyword Expansion -- Natural Enemies, Previous: The Flying Fish Approach -- A Simpler Way To Do It, Up: Going Out On A Limb (How To Work With Branches And Survive)

### Branches And Keyword Expansion - Natural Enemies

If your files contain RCS keywords that expand differently on branch and trunk, you're almost guaranteed to get spurious conflicts on every merge. Even if nothing else changed, the keywords are overlapping, and their expansions won't match. For example, if README.txt contains this on the trunk

         $Revision: 1.14 $

and this on the branch

         $Revision: 1.14.2.1 $

then when the merge is performed, you'll get the following conflict:

         floss$ cvs update -j Exotic_Greetings-branch
         RCS file: /usr/local/newrepos/myproj/README.txt,v
         retrieving revision 1.14
         retrieving revision 1.14.2.1
         Merging differences between 1.14 and 1.14.2.1 into README.txt
         rcsmerge: warning: conflicts during merge
         floss$ cat README.txt
          ...
         <<<<<<< README.txt
         key $Revision: 1.14 $
         =======
         key $Revision: 1.14.2.1 $
         >>>>>>> 1.14.2.1
          ...
         floss$

To avoid this, you can temporarily disable expansion by passing the -kk option (I don't know what it stands for; "kill keywords" maybe?) when you do the merge:

         floss$ cvs update -kk -j Exotic_Greetings-branch
         RCS file: /usr/local/newrepos/myproj/README.txt,v
         retrieving revision 1.14
         retrieving revision 1.14.2.1
         Merging differences between 1.14 and 1.14.2.1 into README.txt
         floss$ cat README.txt
          ...
         $Revision$
          ...
         floss$

There is one thing to be careful of, however: If you use -kk, it overrides whatever other keyword expansion mode you may have set for that file. Specifically, this is a problem for binary files, which are normally -kb (which suppresses all keyword expansion and line-end conversion). So if you have to merge binary files in from a branch, don't use -kk. Just deal with the conflicts by hand instead.

Node: Tracking Third-Party Sources (Vendor Branches), Next: Exporting For Public Distribution, Previous: Going Out On A Limb (How To Work With Branches And Survive), Up: Advanced CVS

### Tracking Third-Party Sources (Vendor Branches)

Sometimes a site will make local changes to a piece of software received from an outside source. If the outside source does not incorporate the local changes (and there might be many legitimate reasons why it can't), the site has to maintain its changes in each received upgrade of the software.

CVS can help with this task, via a feature known as vendor branches. In fact, vendor branches are the explanation behind the puzzling (until now) final two arguments to cvs import: the vendor tag and release tag that I glossed over in An Overview of CVS.

Here's how it works. The initial import is just like any other initial import of a CVS project (except that you'll want to choose the vendor tag and release tag with a little care):

         floss$ pwd
         /home/jrandom/theirproj-1.0
         floss$ cvs import -m "Import of TheirProj 1.0" theirproj Them THEIRPROJ_1_0
         N theirproj/INSTALL
         N theirproj/README
         N theirproj/src/main.c
         N theirproj/src/parse.c
         N theirproj/src/digest.c
         N theirproj/doc/random.c
         N theirproj/doc/manual.txt

         No conflicts created by this import

         floss$

Then you check out a working copy somewhere, make your local modifications, and commit:

         floss$ cvs -q co theirproj
         U theirproj/INSTALL
         U theirproj/README
         U theirproj/doc/manual.txt
         U theirproj/doc/random.c
         U theirproj/src/digest.c
         U theirproj/src/main.c
         U theirproj/src/parse.c
         floss$ cd theirproj
         floss$ emacs src/main.c src/digest.c
          ...
         floss$ cvs -q update
         M src/digest.c
         M src/main.c
         floss$ cvs -q ci -m "changed digestion algorithm; added comment to main"
         Checking in src/digest.c;
         /usr/local/newrepos/theirproj/src/digest.c,v  <--  digest.c
         new revision: 1.2; previous revision: 1.1
         done
         Checking in src/main.c;
         /usr/local/newrepos/theirproj/src/main.c,v  <--  main.c
         new revision: 1.2; previous revision: 1.1
         done
         floss$

A year later, the next version of the software arrives from Them, Inc., and you must incorporate your local changes into it. Their changes and yours overlap slightly. They've added one new file, modified a couple of files that you didn't touch, but also modified two files that you modified.

First you must do another import, this time from the new sources. Almost everything is the same as it was in the initial import - you're importing to the same project in the repository, and on the same vendor branch. The only thing different is the release tag:

         floss$ pwd
         /home/jrandom/theirproj-2.0
         floss$ cvs -q import -m "Import of TheirProj 2.0" theirproj Them THEIRPROJ_2_0
         U theirproj/INSTALL
         N theirproj/TODO
         U theirproj/README
         cvs import: Importing /usr/local/newrepos/theirproj/src
         C theirproj/src/main.c
         U theirproj/src/parse.c
         C theirproj/src/digest.c
         cvs import: Importing /usr/local/newrepos/theirproj/doc
         U theirproj/doc/random.c
         U theirproj/doc/manual.txt

         2 conflicts created by this import.
         Use the following command to help the merge:

                cvs checkout -jThem:yesterday -jThem theirproj

         floss$

My goodness - we've never seen CVS try to be so helpful. It's actually telling us what command to run to merge the changes. And it's almost right, too! Actually, the command as given works (assuming that you adjust yesterday to be any time interval that definitely includes the first import but not the second), but I mildly prefer to do it by release tag instead:

         floss$ cvs checkout -j THEIRPROJ_1_0 -j THEIRPROJ_2_0 theirproj
         cvs checkout: Updating theirproj
         U theirproj/INSTALL
         U theirproj/README
         U theirproj/TODO
         cvs checkout: Updating theirproj/doc
         U theirproj/doc/manual.txt
         U theirproj/doc/random.c
         cvs checkout: Updating theirproj/src
         U theirproj/src/digest.c
         RCS file: /usr/local/newrepos/theirproj/src/digest.c,v
         retrieving revision 1.1.1.1
         retrieving revision 1.1.1.2
         Merging differences between 1.1.1.1 and 1.1.1.2 into digest.c
         rcsmerge: warning: conflicts during merge
         U theirproj/src/main.c
         RCS file: /usr/local/newrepos/theirproj/src/main.c,v
         retrieving revision 1.1.1.1
         retrieving revision 1.1.1.2
         Merging differences between 1.1.1.1 and 1.1.1.2 into main.c
         U theirproj/src/parse.c
         floss$

Notice how the import told us that there were two conflicts, but the merge only seems to claim one conflict. It seems that CVS's idea of a conflict is a little different when importing than at other times. Basically, import reports a conflict if both you and the vendor modified a file between the last import and this one. However, when it comes time to merge, update sticks with the usual definition of "conflict" - overlapping changes. Changes that don't overlap are merged in the usual way, and the file is simply marked as modified.

A quick diff verifies that only one of the files actually has conflict markers:

         floss$ cvs -q update
         C src/digest.c
         M src/main.c
         floss$ cvs diff -c
         Index: src/digest.c
         ===================================================================
         RCS file: /usr/local/newrepos/theirproj/src/digest.c,v
         retrieving revision 1.2
         diff -c -r1.2 digest.c
         *** src/digest.c        1999/07/26 08:02:18     1.2
         -- src/digest.c        1999/07/26 08:16:15
         ***************
         *** 3,7 ****
         -- 3,11 ----
          void
          digest ()
          {
         + <<<<<<< digest.c
            printf ("gurgle, slorp\n");
         + =======
         +   printf ("mild gurgle\n");
         + >>>>>>> 1.1.1.2
          }
         Index: src/main.c
         ===================================================================
         RCS file: /usr/local/newrepos/theirproj/src/main.c,v
         retrieving revision 1.2
         diff -c -r1.2 main.c
         *** src/main.c  1999/07/26 08:02:18     1.2
         -- src/main.c  1999/07/26 08:16:15
         ***************
         *** 7,9 ****
         -- 7,11 ----
          {
            printf ("Goodbye, world!\n");
          }
         +
         + /* I, the vendor, added this comment for no good reason. */
         floss$

From here, it's just a matter of resolving the conflicts as with any other merge:

         floss$ emacs  src/digest.c  src/main.c
          ...
         floss$ cvs -q update
         M src/digest.c
         M src/main.c
         floss$ cvs diff src/digest.c
         cvs diff src/digest.c
         Index: src/digest.c
         ===================================================================
         RCS file: /usr/local/newrepos/theirproj/src/digest.c,v
         retrieving revision 1.2
         diff -r1.2 digest.c
         6c6
         <   printf ("gurgle, slorp\n");
         --
         >   printf ("mild gurgle, slorp\n");
         floss$

Then commit the changes

         floss$ cvs -q ci -m "Resolved conflicts with import of 2.0"
         Checking in src/digest.c;
         /usr/local/newrepos/theirproj/src/digest.c,v  <--  digest.c
         new revision: 1.3; previous revision: 1.2
         done
         Checking in src/main.c;
         /usr/local/newrepos/theirproj/src/main.c,v  <--  main.c
         new revision: 1.3; previous revision: 1.2
         done
         floss$

and wait for the next release from the vendor. (Of course, you'll also want to test that your local modifications still work!)

-------------------------------------------------------------

Node: Exporting For Public Distribution, Next: The Humble Guru, Previous: Tracking Third-Party Sources (Vendor Branches), Up: Advanced CVS

### Exporting For Public Distribution

CVS is a good distribution mechanism for developers, but most users will obtain the software through a downloadable package instead. This package is generally not a CVS working copy - it's just a source tree that can be easily configured and compiled on the user's system.

However, CVS does offer a mechanism to help you create that package, namely the `cvs export` command. To export a project is just like checking out a working copy of the project, except that it checks out the project tree without any `CVS` administrative subdirectories. That is to say, you don't get a working copy, you just get a source tree that knows nothing about where it came from or what the CVS versions of its files are. Thus, the exported copy is just like what the public sees after it downloads and unpacks a distribution. Assuming the project is arranged to be directly compilable from a working copy (and it certainly should be!), then it will still be compilable from the exported copy.

The `export` command works like `checkout`, except that it requires a tag name or date. For example, here we tag the project with a release name, and then export based on that:

         floss$ pwd
         /home/jrandom/myproj
         floss$ cvs -q tag R_1_0
         T README.txt
         T hello.c
         T a-subdir/whatever.c
         T a-subdir/subsubdir/fish.c
         T b-subdir/random.c
         floss$ cd ..
         floss$ cvs -d /usr/local/newrepos -q export -r R_1_0 -d myproj-1.0 myproj
         U myproj-1.0/README.txt
         U myproj-1.0/hello.c
         U myproj-1.0/a-subdir/whatever.c
         U myproj-1.0/a-subdir/subsubdir/fish.c
         U myproj-1.0/b-subdir/random.c
         floss$ cd myproj-1.0
         floss$ ls
         README.txt  a-subdir  b-subdir  hello.c

Notice how, since the `export` command is not invoked from within a working copy, it's necessary to use the global `-d` option to tell CVS which repository to use. Also, in this particular example, we exported into an explicitly named directory (`myproj-1.0`) instead of defaulting to the project's name (`myproj`), since there was a working copy of that name already present. This situation is not uncommon.

After the exported copy is created, as in the above example, the following might be sufficient to complete the release, if the project is a simple one:

         floss$ tar cf myproj-1.0.tar myproj-1.0
         floss$ gzip --best myproj-1.0.tar
         floss$ ls
         myproj/   myproj-1.0/   myproj-1.0.tar.gz
         floss$ rm -rf myproj-1.0
         floss$ mv myproj-1.0.tar.gz /home/ftp/pub/myproj/

Of course, running all of these commands by hand is rare. More often, `cvs export` is called from within some script that handles all aspects of release and packaging process. Given that there are often several "test" releases leading up to each public release, it is desirable that the procedures for creating a releasable package be highly automated.

Node: The Humble Guru, Previous: Exporting For Public Distribution, Up: Advanced CVS

### The Humble Guru

If you read and understood (and better yet, experimented with) everything in this chapter, you may rest assured that there are no big surprises left for you in CVS - at least until someone adds a major new feature to CVS. Everything you need to know to use CVS on a major project has been presented.

Before that goes to your head, let me reiterate the suggestion, first made in Chapter 4, that you subscribe to the info-cvs@gnu.org mailing list. Despite having the impoverished signal-to-noise ratio common to most Internet mailing lists, the bits of signal that do come through are almost always worth the wait. I was subscribed during the entire time I wrote this chapter (indeed, for all previous chapters as well), and you would be amazed to know how many important details I learned about CVS's behavior from reading other people's posts. If you're going to be using CVS seriously, and especially if you're the CVS administrator for a group of developers, you can benefit a lot from the shared knowledge of all the other serious users out there.

Node: Tips And Troubleshooting, Next: CVS Reference, Previous: Advanced CVS, Up: Top

## Tips And Troubleshooting

I've said in earlier chapters that CVS is not "black box" software. Black boxes don't let you peek inside; they don't give you internal access so that you can fix (or break) things. The premise is that the black box usually doesn't need to be fixed. Most of the time, the software should work perfectly, so users don't need internal access. But when black boxes do fail, they tend to fail completely. Any problem at all is a showstopper, because there aren't many options for repair.

CVS is more like a perfectly transparent box - except without the box. Its moving parts are exposed directly to the environment, not hermetically sealed off, and bits of that environment (unexpected file permissions, interrupted commands, competing processes, whatever) can sometimes get inside the mechanism and gum up the gears. But even though CVS does not always work perfectly, it rarely fails completely, either. It has the advantage of graceful degradation; the degree to which it doesn't work is usually proportional to the number and severity of problems in its environment. If you know enough about what CVS is trying to do - and how it's trying to do it - you'll know what to do when things go wrong.

Although I can't list all of the problems that you might encounter, I've included some of the more common ones here. This chapter is divided into two sections: The first describes those parts of the environment to which CVS is most sensitive (mainly repository permissions and the working copy administrative area), and the second describes some of the most frequently encountered problems and their solutions. By seeing how to handle these common situations, you will get a feeling for how to approach any unexpected problem in CVS.

Node: The Usual Suspects, Next: General Troubleshooting Tips, Up: Tips And Troubleshooting

### The Usual Suspects

As a CVS administrator (read "field doctor"), you will find that 90 percent of your users' problems are caused by inconsistent working copies, and the other 90 percent by incorrect repository permissions. Therefore, before looking at any specific situations, I'll give a quick overview of the working copy administrative area and review a few important things about repository permissions.

Node: The Working Copy Administrative Area, Next: Repository Permissions, Up: The Usual Suspects

### The Working Copy Administrative Area

You've already seen the basics of working copy structure in An Overview of CVS; in this section, we'll go into a bit more detail. Most of the details concern the files in the CVS/ administrative subdirectories. You already know about Entries, Root, and Repository, but the CVS/ subdirectory can also contain other files, depending on the circumstances. I'll describe those other files here, partly so they don't surprise you when you encounter them, and partly so you can fix them if they ever cause trouble.

### `CVS/Entries.Log`

Sometimes, a file named `CVS/Entries.Log` will mysteriously appear. The sole purpose of this file is to temporarily cache minor changes to CVS/Entries, until some operation significant enough to be worth rewriting the entire Entries file comes along. CVS has no ability to edit the Entries file in place; it must read the entire file in and write it back out to make any change. To avoid this effort, CVS sometimes records small changes in Entries.Log, until the next time it needs to rewrite Entries.

The format of Entries.Log is like Entries, except for an extra letter at the beginning of each line. `A` means that the line is to be added to the main Entries file, and `R` means it is to be removed.

For the most part, you can ignore Entries.Log; it's rare that a human has to understand the information it contains. However, if you're reading over an Entries file to debug some problem in a working copy, you should also examine Entries.Log.

### `CVS/Entries.Backup`

The CVS/Entries.Backup file is where CVS actually writes out a new Entries file, before renaming it to `Entries` (similar to the way it writes to temporary RCS files in the repository and then moves them to their proper name when they're complete). Because it becomes Entries when it's complete, you'll rarely see an Entries.Backup file; if you do see one, it probably means CVS got interrupted in the middle of some operation.

### `CVS/Entries.Static`

If the CVS/Entries.Static file exists, it means that the entire directory has not been fetched from the repository. (When CVS knows a working directory is in an incomplete state, it will not bring additional files into that directory.)

The Entries.Static file is present during checkouts and updates and removed immediately when the operation is complete. If you see Entries.Static, it means that CVS was interrupted, and its presence prevents CVS from creating any new files in the working copy. (Often, running `cvs update -d` solves the problem and removes Entries.Static.)

The absence of Entries.Static does not necessarily imply that the working copy contains all of the project's files. Whenever a new directory is created in the project's repository, and someone updates their working copy without passing the -d flag to update, the new directory will not be created in the working copy. Locally, CVS is unaware that there is a new directory in the repository, so it goes ahead and removes the Entries.Static file when the update is complete, even though the new directory is not present in the working copy.

### `CVS/Tag`

If the CVS/Tag file is present, it names a tag associated, in some sense, with the directory. I say "in some sense" because, as you know, CVS does not actually keep any revision history for directories and, strictly speaking, cannot attach tags to them. Tags are attached to regular files only or, more accurately, to particular revisions in regular files.

However, if every file in a directory is on a particular tag, CVS likes to think of the entire directory as being on the tag, too. For example, if you were to check out a working copy on a particular branch:

         floss$ cvs co -r Bugfix_Branch_1

and then add a file inside it, you'd want the new file's initial revision to be on that branch, too. For similar reasons, CVS also needs to know if the directory has a nonbranch sticky tag or date set on it.

Tag files contain one line. The first character on the line is a single-letter code telling what kind of tag it is, and the rest of the line is the tag's name. Currently, CVS uses only these three single-letter codes:

- T - A branch tag
- N - A nonbranch (regular) tag
- D - A sticky date, which occurs if a command such as

                floss$ cvs checkout -D 1999-05-15 myproj

  or

                floss$ cvs update -D 1999-05-15 myproj

  is run.

(If you see some other single-letter code, it just means that CVS has added a new tag type since this chapter was written.)

You should not remove the Tag file manually; instead, use `cvs update -A`.

### Rarities

There are a few other files you may occasionally find in a CVS/ subdirectory:

- CVS/Checkin.prog, CVS/Update.prog
- CVS/Notify, CVS/Notify.tmp
- CVS/Base/, CVS/Baserev, CVS/Baserev.tmp
- CVS/Template

These files are usually not the cause of problems, so I'm just listing them (see CVS Reference for their full descriptions).

### Portability And Future Extension

As features are added to CVS, new files (not listed here) may appear in working copy administrative areas. As new files are added, they'll probably be documented in the Cederqvist manual, in the node Working Directory Storage. You can also start looking in src/cvs.h in the source distribution, if you prefer to learn from code.

Finally, note that all CVS/* files - present and future - use whatever line-ending convention is appropriate for the working copy's local system (for example, LF for Unix or CRLF for Windows). This means that if you transport a working copy from one kind of machine to the other, CVS won't be able to handle it (but then, you'd have other problems, because the revision-controlled files themselves would have the wrong line-end conventions for their new location).

Node: Repository Permissions, Previous: The Working Copy Administrative Area, Up: The Usual Suspects

### Repository Permissions

CVS does not require any particular repository permission scheme - it can handle a wide variety of permission arrangements. However, to avoid getting confusing behaviors, you should make sure your repository setup meets at least the following criteria:

- If a user wants any kind of access at all - even read-only access - to a given subdirectory of the repository, she usually needs file system-level write permission to that subdirectory. This is necessary because CVS creates temporary lock files in the repository to ensure data consistency. Even read-only operations (such as checkout or update) create locks, to signal that they need the data to stay in one state until they're done.

  As noted in Repository Administration, you can get around this writeability requirement by setting the LockDir parameter in CVSROOT/config, like this:

                LockDir=/usr/local/cvslocks

  Of course, then you would need to make sure the directory /usr/local/cvslocks is writeable by all CVS users. Either way, most CVS operations, including read-only ones, are going to require a writeable directory somewhere. By default, that directory is the project's repository; if you're very security conscious, you can change it to be somewhere else.

- Make sure the CVSROOT/history file is world-writeable (if it exists at all). If the history file exists, most CVS operations attempt to append a record to it; if the attempt fails, the operation exits with an error.

  Unfortunately (and inexplicably), the history file is not born world-writeable when you create a new repository with cvs init. At least with the current version of CVS, you should explicitly change its permissions after you create a new repository (or just remove it, if you want to disable history logging entirely).

  (This problem may go away - I just now submitted a patch to the CVS maintainers that makes the history file world-writeable when you initialize a new repository. So perhaps if you get a more recent version of CVS than the one available now (September 1999), it won't be a problem for you.)

- For security purposes, you almost certainly want to make sure that most CVS users do not have Unix-level write access to the CVSROOT directory in the repository. If someone has checkin access to CVSROOT, they can edit commitinfo, loginfo, or any of the other trigger files to invoke a program of their choice - they could even commit a new program if the one they want isn't on the system already. Therefore, you should assume that anyone who has commit access to CVSROOT is able to run arbitrary commands on the system.

Node: General Troubleshooting Tips, Next: Some Real Life Problems (With Solutions), Previous: The Usual Suspects, Up: Tips And Troubleshooting

### General Troubleshooting Tips

The bulk of this chapter is organized into a series of questions and answers, similar to an Internet FAQ (Frequently Asked Questions) document. These are all based on actual CVS experiences. But before we look at individual cases, let's take a moment to consider CVS troubleshooting from a more general point of view.

The first step in solving a CVS problem is usually to determine whether it's a working copy or repository problem. The best technique for doing that, not surprisingly, is to see if the problem occurs in working copies other than the one where it was first noticed. If it does, it's likely a repository issue; otherwise, it's probably just a local issue.

Working copy problems tend to be encountered more frequently, not because working copies are somehow less reliable than repositories, but because each repository usually has many working copies. Although most working copy knots can be untied with enough patience, you may occasionally find it more time-efficient simply to delete the working copy and check it out again.

Of course, if checking out again takes too long, or there is considerable uncommitted state in the working copy that you don't want to lose, or if you just want to know what's wrong, it's worth digging around to find the cause of the problem. When you start digging around, one of the first places to look is in the CVS/ subdirectories. Check the file contents and the file permissions. Very occasionally, the permissions can mysteriously become read-only or even unreadable. (I suspect this is caused by users accidentally mistyping Unix commands rather than any mistake on CVS's part.)

Repository problems are almost always caused by incorrect file and directory permissions. If you suspect a problem may be due to bad repository permissions, first find out the effective repository user ID of the person who's having the trouble. For all local and most remote users, this is either their regular username or the username they specified when they checked out their working copy. If they're using the pserver method with user-aliasing (see the section Anonymous Access in Repository Administration), the effective user ID is the one on the right in the CVSROOT/passwd file. Failure to discover this early on can cause you to waste a lot of time debugging the wrong thing.

And now, without further ado...

Node: Some Real Life Problems (With Solutions), Previous: General Troubleshooting Tips, Up: Tips And Troubleshooting

### Some Real Life Problems (With Solutions)

All of these situations are ones I've encountered in my real-life adventures as a CVS troubleshooter (plus a few items that are not really problems, just questions that I've heard asked so often that they may as well be answered here). The list is meant to be fairly comprehensive, and it may repeat material you've seen in earlier chapters.

The situations are listed according to how frequently they seem to arise, with the most common ones first.

Node: CVS says it is waiting for a lock; what does that mean?, Next: CVS claims a file is failing Up-To-Date check; what do I do?, Up: Some Real Life Problems (With Solutions)

### CVS says it is waiting for a lock; what does that mean?

If you see a message like this

         cvs update: [22:58:26] waiting for qsmith's lock in /usr/local/newrepos/myproj

it means you're trying to access a subdirectory of the repository that is locked by some other CVS process at the moment. A process is being run in that directory so it may not be in a consistent state for other CVS processes to use.

However, if the wait message persists for a long time, it probably means that a CVS process failed to clean up after itself, for whatever reason. It can happen when CVS dies suddenly and unexpectedly, say, due to a power failure on the repository machine.

The solution is to remove the lock files by hand from the repository subdirectory in question. Go into that part of the repository and look for files named `#cvs.lock` or that begin with `#cvs.wfl` or `#cvs.rfl`. Compare the file's timestamps with the start times of any currently running CVS processes. If the files could not possibly have been created by any of those processes, it's safe to delete them. The waiting CVS processes eventually notice when the lock files are gone - this should take about 30 seconds - and allow the requested operation to proceed.

See the node Locks in the Cederqvist manual for more details.

Node: CVS claims a file is failing Up-To-Date check; what do I do?, Next: The pserver access method is not working, Previous: CVS says it is waiting for a lock; what does that mean?, Up: Some Real Life Problems (With Solutions)

### CVS claims a file is failing Up-To-Date check; what do I do?

Don't panic - it just means that the file has changed in the repository since the last time you checked it out or updated it.

Run `cvs update` on the file to merge in the changes from the repository. If the received changes conflict with your local changes, edit the file to resolve the conflict. Then try your commit again - it will succeed, barring the possibility that someone committed yet another revision while you were busy merging the last changes.

Node: The pserver access method is not working, Next: The pserver access method is STILL not working, Previous: CVS claims a file is failing Up-To-Date check; what do I do?, Up: Some Real Life Problems (With Solutions)

### The pserver access method is not working

The most common, less obvious cause of this problem is that you forgot to list the repository using an `--allow-root` option in your inetd configuration file.

Recall this example /etc/inetd.conf line from Repository Administration:

         cvspserver stream tcp nowait root /usr/local/bin/cvs cvs \
                   --allow-root=/usr/local/newrepos pserver

(In the actual file, this is all one long line, with no backslash.)

The `--allow-root=/usr/local/newrepos` portion is a security measure, to make sure that people can't use CVS to get pserver access to repositories that are not supposed to be served remotely. Any repository intended to be accessible via pserver must be mentioned in an `--allow-root`. You can have as many different `--allow-root` options as you need for all of your system's repositories (or anyway, as many as you want until you bump up against your inetd's argument limit).

See Repository Administration for more details on setting up the password-authenticating server.

Node: The pserver access method is STILL not working, Next: My commits seem to happen in pieces instead of atomically, Previous: The pserver access method is not working, Up: Some Real Life Problems (With Solutions)

### The pserver access method is STILL not working

Okay, if the problem is not a missing `--allow-root`, here are a few other possibilities:

- The user has no entry in the CVSROOT/passwd file, and the CVSROOT/config file has SystemAuth=no so CVS will not fall back on the system password file (or SystemAuth=yes, but the system password file has no entry for this user either).
- The user has an entry in the CVSROOT/passwd file, but there is no user by that name on the system, and the CVSROOT/passwd entry does not map the user to any valid system username.
- The password is wrong (but CVS is usually pretty good about informing the user of this, so that's probably not the answer).
- Everything is set up correctly with the passwd files and in /etc/inetd.conf, but you forgot an entry like this in /etc/services:

                cvspserver      2401/tcp

  so inetd is not even listening on that port to pass connections off to CVS.

Node: My commits seem to happen in pieces instead of atomically, Next: CVS keeps changing file permissions; why does it do that?, Previous: The pserver access method is STILL not working, Up: Some Real Life Problems (With Solutions)

### My commits seem to happen in pieces instead of atomically

That's because CVS commits happen in pieces, not atomically. :-)

More specifically, CVS operations happen directory by directory. When you do a commit (or an update, or anything else, for that matter) spanning multiple directories, CVS locks each corresponding repository directory in turn while it performs the operation for that directory.

For small- to medium-sized projects, this is rarely a problem - CVS manages to do its thing in each directory so quickly that you never notice the nonatomicity. Unfortunately, in large projects, scenarios like the following can occur (imagine this taking place in a project with at least two deep, many-filed subdirectories, A and B):

1. User qsmith starts a commit, involving files from both subdirectories. CVS commits the files in B first (perhaps because qsmith specified the directories on the command line in that order).
2. User jrandom starts a cvs update. The update, for whatever reason, starts with working copy directory A (CVS makes no guarantees about the order in which it processes directories or files, if left to its own devices). Note that there is no locking contention, because qsmith is not active in A yet.
3. Then, qsmith's commit finishes B, moves on to A, and finishes A.
4. Finally, jrandom's update moves on to B and finishes it.

Clearly, when this is all over, jrandom's working copy reflects qsmith's changes to B but not A. Even though qsmith intended the changes to be committed as a single unit, it didn't happen that way. Now jrandom's working copy is in a state that qsmith never anticipated.

The solution, of course, is for jrandom to do another cvs update to fetch the uncaught changes from qsmith's commit. However, that assumes that jrandom has some way of finding out in the first place that he only got part of qsmith's changes.

There's no easy answer to this quandary. You simply have to hope that the inconsistent state of the working copy will somehow become apparent (maybe the software won't build, or jrandom and qsmith will have a conversation that's confusing until they realize what must have happened).

CVS's failure to provide atomic transaction guarantees is widely considered a bug. The only reason that locks are not made at the top level of the repository is that this would result in intolerably frequent lock contentions for large projects with many developers. Therefore, CVS has chosen the lesser of two evils, reducing the contention frequency but allowing the possibility of interleaved reads and writes. Someday, someone may modify CVS (say, speeding up repository operations) so that it doesn't have to choose between two evils; until then, we're stuck with nonatomic actions.

For more information, see the node Concurrency in the Cederqvist manual.

Node: CVS keeps changing file permissions; why does it do that?, Next: CVS on Windows complains it cannot find my .cvspass file; why?, Previous: My commits seem to happen in pieces instead of atomically, Up: Some Real Life Problems (With Solutions)

### CVS keeps changing file permissions; why does it do that?

In general, CVS doesn't do a very good job of preserving permissions on files. When you import a project and then check it out, there is no guarantee that the file permissions in the new working copy will be the same as when the project was imported. More likely, the working copy files will be created with the same standard permissions that you normally get on newly created files.

However, there is at least one exception. If you want to store executable shell scripts in the project, you can keep them executable in all working copies by making the corresponding repository file executable:

         floss$ ls -l /usr/local/newrepos/someproj
         total 6
         -r--r--r--   1 jrandom  users         630 Aug 17 01:10 README.txt,v
         -r-xr-xr-x   1 jrandom  users        1041 Aug 17 01:10 scrub.pl,v*
         -r--r--r--   1 jrandom  users         750 Aug 17 01:10 hello.c,v

Notice that although the file is executable, it is still read-only, as all repository files should be (remember that CVS works by making a temporary copy of the RCS file, doing everything in the copy, and then replacing the original with the copy when ready).

When you import or add an executable file, CVS preserves the executable bits, so if the permissions were correct from the start, you have nothing to worry about. However, if you accidentally add the file before making it executable, you must go into the repository and manually set the RCS file to be executable.

The repository permissions always dominate. If the file is nonexecutable in the repository, but executable in the working copy, the working copy file will also be nonexecutable after you do an update. Having your files' permissions silently change can be extremely frustrating. If this happens, first check the repository and see if you can solve it by setting the appropriate permissions on the corresponding RCS files.

A feature called `PreservePermissions` has recently been added to CVS that may alleviate some of these problems. However, using this feature can cause other unexpected results (which is why I'm not recommending it unconditionally here). Make sure you read the nodes config and Special Files in the Cederqvist before putting `PreservePermissions=yes` in CVSROOT/config.

Node: CVS on Windows complains it cannot find my .cvspass file; why?, Next: My working copy is on several different branches; help?, Previous: CVS keeps changing file permissions; why does it do that?, Up: Some Real Life Problems (With Solutions)

### CVS on Windows complains it cannot find my .cvspass file; why?

For pserver connections, CVS on the client side tries to find the .cvspass file in your home directory. Windows machines don't have a natural "home" directory, so CVS consults the environment variable `%HOME%`. However, you have to be very careful about how you set HOME. This will work:

         set HOME=C:

This will not:

         set HOME=C:\

That extra backslash is enough to confuse CVS, and it will be unable to open `C:\\.cvspass`.

So, the quick and permanent solution is to put

         set HOME=C:

into your autoexec.bat and reboot. CVS pserver should work fine after that.

Node: My working copy is on several different branches; help?, Next: When I do export -d I sometimes miss recent commits, Previous: CVS on Windows complains it cannot find my .cvspass file; why?, Up: Some Real Life Problems (With Solutions)

### My working copy is on several different branches; help?

You mean different subdirectories of your working copy somehow got on different branches? You probably ran updates with the -r flag, but from places other than the top level of the working copy.

No big deal. If you want to return to the trunk, just run this

         cvs update -r HEAD

or this

         cvs update -A

from the top directory. Or, if you want to put the whole working copy on one of the branches, do this:

         cvs update -r Branch_Name

There's nothing necessarily wrong with having one or two subdirectories of your working copy on a different branch than the rest of it, if you need to do some temporary work on that branch just in those locations. However, it's usually a good idea to switch them back when you're done - life is much less confusing when your whole working copy is on the same line of development.

Node: When I do export -d I sometimes miss recent commits, Next: I get an error about val-tags; what should I do?, Previous: My working copy is on several different branches; help?, Up: Some Real Life Problems (With Solutions)

### When I do export -d I sometimes miss recent commits

This is due to a clock difference between the repository and local machines. You can solve it by resetting one or both of the clocks, or specifying a different date as the argument to -D. It's perfectly acceptable to specify a date in the future (such as -D tomorrow), if that's what it takes to compensate for the time difference.

Node: I get an error about val-tags; what should I do?, Next: I am having problems with sticky tags; how do I get rid of them?, Previous: When I do export -d I sometimes miss recent commits, Up: Some Real Life Problems (With Solutions)

### I get an error about val-tags; what should I do?

If you see an error like this:

         cvs [export aborted]: cannot write /usr/local/myproj/CVSROOT/val-tags: \
            Operation not permitted

it means the user CVS is running as does not have permission to write to the CVSROOT/val-tags file. This file stores valid tag names, to give CVS a fast way to determine what tags are valid. Unfortunately, CVS sometimes modifies this file even for operations that are read-only with respect to the repository, such as checking out a project.

This is a bug in CVS and may be fixed by the time you read this. Until then, the solution is either to make val-tags world-writeable or, failing that, to remove it or change its ownership to the user running the CVS operation. (You'd think just changing the permissions would be enough, but on several occasions I've had to change the ownership, too.)

Node: I am having problems with sticky tags; how do I get rid of them?, Next: Checkouts/updates exit with error saying cannot expand modules, Previous: I get an error about val-tags; what should I do?, Up: Some Real Life Problems (With Solutions)

### I am having problems with sticky tags; how do I get rid of them?

Various CVS operations cause the working copy to have a sticky tag, meaning a single tag that corresponds to each revision for each file (in the case of a branch, the sticky tag is applied to any new files added in the working copy). You get a sticky tagged working area whenever you check out or update by tag or date, for example:

         floss$ cvs update -r Tag_Name

or

         floss$ cvs checkout -D '1999-08-16'

If a date or a nonbranch tag name is used, the working copy will be a frozen snapshot of that moment in the project's history - so naturally you will not be able to commit any changes from it.

To remove a sticky tag, run update with the -A flag

         floss$ cvs update -A

which clears all the sticky tags and updates each file to its most recent trunk revision.

Node: Checkouts/updates exit with error saying cannot expand modules, Next: I cannot seem to turn off watches, Previous: I am having problems with sticky tags; how do I get rid of them?, Up: Some Real Life Problems (With Solutions)

### Checkouts/updates exit with error saying cannot expand modules

This is just a case of a bad error message in CVS; probably someone will get around to fixing it sooner or later, but meanwhile it may bite you. The error message looks something like this:

         floss$ cvs co -d bwf-misc user-space/bwf/writings/misc
         cvs server: cannot find module `user-space/bwf/writings/misc' - ignored
         cvs [checkout aborted]: cannot expand modules

CVS appears to be saying that there's something wrong with the CVSROOT/modules file. However, what's really going on is a permission problem in the repository. The directory I'm trying to check out isn't readable, or one of its parents isn't readable. In this case, it was a parent:

         floss$ ls -ld /usr/local/cvs/user-space/bwf

         drwx------  19 bwf      users        1024 Aug 17 01:24 bwf/

Don't let that egregiously wrong error message fool you - this is a repository permission problem.

Node: I cannot seem to turn off watches, Next: My binary files are messed up, Previous: Checkouts/updates exit with error saying cannot expand modules, Up: Some Real Life Problems (With Solutions)

### I cannot seem to turn off watches

You probably did

         floss$ cvs watch remove

on all the files, but forgot to also do:

         floss$ cvs watch off

A hint for diagnosing watch problems: Sometimes it can be immensely clarifying to just go into the repository and examine the CVS/fileattr files directly. See Repository Administration for more information about them.

Node: My binary files are messed up, Next: CVS is not doing line-end conversion correctly, Previous: I cannot seem to turn off watches, Up: Some Real Life Problems (With Solutions)

### My binary files are messed up

Did you remember to use -kb when you added them? If not, CVS may have performed line-end conversion or RCS keyword substitution on them. The easiest solution is usually to mark them as binary

         floss$ cvs admin -kb foo.gif

and then commit a fixed version of the file. CVS will not corrupt the new commit or any of the commits thereafter, because it now knows the file is binary.

Node: CVS is not doing line-end conversion correctly, Next: I need to remove a subdirectory in my project; how do I do it?, Previous: My binary files are messed up, Up: Some Real Life Problems (With Solutions)

### CVS is not doing line-end conversion correctly

If you're running the CVS client on a non-Unix platform and are not getting the line-end conventions that you want in some working copy files, it's usually because they were accidentally added with -kb when they shouldn't have been. This can be fixed in the repository with, believe it or not, the command:

         floss$ cvs admin -kkv FILE

The -kkv means to do normal keyword substitution and implies normal line-end conversions as well. (Internally, CVS is a bit confused about the difference between keyword substitution and line-end conversion. This confusion is reflected in the way the -k options can control both parameters.)

Unfortunately, that admin command only fixes the file in the repository - your working copy still thinks the file is binary. You can hand edit the CVS/Entries line for that file, removing the -kb, but that won't solve the problem for any other working copies out there.

Node: I need to remove a subdirectory in my project; how do I do it?, Next: Can I copy .cvspass files or portions of them?, Previous: CVS is not doing line-end conversion correctly, Up: Some Real Life Problems (With Solutions)

### I need to remove a subdirectory in my project; how do I do it?

Well, you can't exactly remove the subdirectory, but you can remove all of the files in it (first remove them, then cvs remove them, and then commit). Once the directory is empty, people can have it automatically pruned out of their working copies by passing the -P flag to update.

Node: Can I copy .cvspass files or portions of them?, Next: I just committed some files with the wrong log message, Previous: I need to remove a subdirectory in my project; how do I do it?, Up: Some Real Life Problems (With Solutions)

### Can I copy .cvspass files or portions of them?

Yes, you can. You can copy `.cvspass` files from machine to machine, and you can even copy individual lines from one .cvspass file to another. For high-latency servers, this may be faster than running cvs login from each working copy machine.

Remember that if you transport a .cvspass file between two machines with different line-ending conventions, it probably won't work (of course, you can probably do the line-end conversion manually without too much trouble).

Node: I just committed some files with the wrong log message, Next: I need to move files around without losing revision history, Previous: Can I copy .cvspass files or portions of them?, Up: Some Real Life Problems (With Solutions)

### I just committed some files with the wrong log message

You don't need to hand-edit anything in the repository to solve this. Just run admin with the -m flag. Remember to have no space between -m and its argument, and to quote the replacement log message as you would a normal one:

         floss$ cvs admin -m1.17:'I take back what I said about the customer.' hello.c

Node: I need to move files around without losing revision history, Next: How can I get a list of all tags in a project?, Previous: I just committed some files with the wrong log message, Up: Some Real Life Problems (With Solutions)

### I need to move files around without losing revision history

In the repository, copy (don't move) the RCS files to the desired new location in the project. They must remain in their old locations as well. Then, in a working copy, do:

         floss$ rm oldfile1 oldfile2 ...
         floss$ cvs remove oldfile1 oldfile2 ...
         floss$ cvs commit -m �Òremoved from here�Ó oldfile1 oldfile2 ...

When people do updates after that, CVS correctly removes the old files and brings the new files into the working copies just as though they had been added to the repository in the usual way (except that they'll be at unusually high revision numbers for supposedly new files).

Node: How can I get a list of all tags in a project?, Next: How can I get a list of all projects in a repository?, Previous: I need to move files around without losing revision history, Up: Some Real Life Problems (With Solutions)

### How can I get a list of all tags in a project?

Currently, there is no convenient way to do this in CVS. The lack is sorely felt by all users, and I believe work is under way to make this feature available. By the time you read this, a `cvs tags` command or something similar may be available.

Until then, there are workarounds. You can run cvs log -h and read the sections of the output following the header `symbolic names:`. Or, if you happen to be on the repository machine, you can just look at the beginnings of some of the RCS files directly in the repository. All of the tags (branches and nonbranches) are listed in the `symbols` field:

         floss$ head /usr/local/newrepos/hello.c,v
         head	2.0;
         access;
         symbols
         	Release_1_0:1.22
         	Exotic_Greetings-2:1.21
         	merged-Exotic_Greetings-1:1.21
         	Exotic_Greetings-1:1.21
         	merged-Exotic_Greetings:1.21
         	Exotic_Greetings-branch:1.21.0.2
         	Root-of-Exotic_Greetings:1.21
         	start:1.1.1.1
         	jrandom:1.1.1;
         locks; strict;
         comment	@ * @;

Node: How can I get a list of all projects in a repository?, Next: Some commands fail remotely but not locally; how should I debug?, Previous: How can I get a list of all tags in a project?, Up: Some Real Life Problems (With Solutions)

### How can I get a list of all projects in a repository?

As with getting a list of tags, this is not implemented in the most current version of CVS, but it's highly likely that it will be implemented soon. I imagine the command will be called cvs list with a short form of cvs ls, and it probably will both parse the modules file and list the repository subdirectories.

In the meantime, examining the CVSROOT/modules file (either directly or by running cvs checkout -c) is probably your best bet. However, if no one has explicitly made a module for a particular project, it won't show up there.

Node: Some commands fail remotely but not locally; how should I debug?, Next: I do not see my problem covered in this chapter, Previous: How can I get a list of all projects in a repository?, Up: Some Real Life Problems (With Solutions)

### Some commands fail remotely but not locally; how should I debug?

Sometimes there's a problem in the communication between the client and the server. If so, it's a bug in CVS, but how would you go about tracking down such a thing?

CVS gives you a way to watch the protocol between the client and server. Before you run the command on the local (working copy) machine, set the environment variable `CVS_CLIENT_LOG`. Here's how in Bourne shell syntax:

         floss$ CVS_CLIENT_LOG=clog; export CVS_CLIENT_LOG

Once that variable is set, CVS will record all communications between client and server in two files whose names are based on the variable's value:

         floss$ ls
         CVS/        README.txt    a-subdir/    b-subdir/    foo.gif     hello.c
         floss$ cvs update
         ? clog.in
         ? clog.out
         cvs server: Updating .
         cvs server: Updating a-subdir
         cvs server: Updating a-subdir/subsubdir
         cvs server: Updating b-subdir
         floss$ ls
         CVS/              a-subdir/    clog.in     foo.gif
         README.txt        b-subdir/    clog.out    hello.c
         floss$

The `clog.in` file contains everything that the client sent into the server, and `clog.out` contains everything the server sent back out to the client. Here are the contents of clog.out, to give you a sense of what the protocol looks like:

         Valid-requests Root Valid-responses valid-requests Repository           \
         Directory Max-dotdot Static-directory Sticky Checkin-prog Update-prog   \
         Entry Kopt Checkin-time Modified Is-modified UseUnchanged Unchanged     \
         Notify Questionable Case Argument Argumentx Global_option Gzip-stream   \
         wrapper-sendme-rcsOptions Set expand-modules ci co update diff log add  \
         remove update-patches gzip-file-contents status rdiff tag rtag import   \
         admin export history release watch-on watch-off watch-add watch-remove  \
         watchers editors init annotate noop
         ok
         M ? clog.in
         M ? clog.out
         E cvs server: Updating .
         E cvs server: Updating a-subdir
         E cvs server: Updating a-subdir/subsubdir
         E cvs server: Updating b-subdir
         ok

The clog.in file is even more complex, because it has to send revision numbers and other per-file information to the server.

There isn't space here to document the client/server protocol, but you can read the `cvsclient` Info pages that were distributed with CVS for a complete description. You may be able to figure out a good deal of it just from reading the raw protocol itself. Although you probably won't find yourself using client logging until you've eliminated all of the other possible causes of a problem, it is an invaluable tool for finding out what's really going on between the client and server.

Node: I do not see my problem covered in this chapter, Next: I think I have discovered a bug in CVS; what do I do?, Previous: Some commands fail remotely but not locally; how should I debug?, Up: Some Real Life Problems (With Solutions)

### I do not see my problem covered in this chapter

Email an accurate and complete description of your problem to info-cvs@gnu.org, the CVS discussion list. Its members are located in many different time zones, and I've usually gotten a response within an hour or two of sending a question. Please join the list by sending email to info-cvs-request@gnu.org, so you can help answer questions, too.

Node: I think I have discovered a bug in CVS; what do I do?, Next: I have implemented a new feature for CVS; to whom do I send it?, Previous: I do not see my problem covered in this chapter, Up: Some Real Life Problems (With Solutions)

### I think I have discovered a bug in CVS; what do I do?

CVS is far from perfect - if you've already tried reading the manual and posting a question on the mailing list, and you still think you're looking at a bug, then you probably are.

Send as complete a description of the bug as you can to bug-cvs@gnu.org (you can also subscribe to that list; just use bug-cvs-request@gnu.org instead). Be sure to include the version number of CVS (both client and server versions, if applicable), and a recipe for reproducing the bug.

If you have written a patch to fix the bug, include it and mention on the subject line of your message that you have a patch. The maintainers will be very grateful.

(Further details about these procedures are outlined in the node BUGS in the Cederqvist manual and the file HACKING in the source distribution.)

Node: I have implemented a new feature for CVS; to whom do I send it?, Next: How can I keep up with changes to CVS?, Previous: I think I have discovered a bug in CVS; what do I do?, Up: Some Real Life Problems (With Solutions)

### I have implemented a new feature for CVS; to whom do I send it?

Same as with a bug: Send the patch to bug-cvs@gnu.org. Make sure you've read over the HACKING file first, though.

Node: How can I keep up with changes to CVS?, Previous: I have implemented a new feature for CVS; to whom do I send it?, Up: Some Real Life Problems (With Solutions)

### How can I keep up with changes to CVS?

The troubleshooting techniques and known bugs described in this chapter are accurate as of (approximately) CVS Version 1.10.7. Things move fast in the CVS world, however. While I was writing the last few chapters, the unofficial mantle of CVS maintainership passed from Cyclic Software to SourceGear, Inc (http://www.sourcegear.com), which purchased Cyclic. SourceGear has publicly announced its intention to take an active role in CVS maintainer-ship and has received Cyclic's approval, which is more or less enough to make it the "lead maintainer" of CVS as of right now. (The http://www.cyclic.com address will continue to work, however, so all of the URLs given previously in this book should remain valid.)

SourceGear is, at this very moment, busy organizing and cleaning up various patches that have been floating around, with the intention of incorporating many of them into CVS. Some of these patches will probably fix bugs listed previously, and others may afford new troubleshooting tools to CVS users.

The best way to stay up to date with what's going on is to read the NEWS file in your CVS distribution, watch the mailing lists, and look for changes to the Cederqvist manual and the online version of this book (http://cvsbook.red-bean.com).

Node: CVS Reference, Next: Third-Party Tools, Previous: Tips And Troubleshooting, Up: Top

## CVS Reference

This chapter is a complete reference to CVS commands, repository administrative files, keyword substitution, run control files, working copy files, and environment variables - everything in CVS as of CVS version 1.10.7 (more accurately, as of August 20, 1999).

Node: Commands And Options, Next: Keyword Substitution (RCS Keywords), Up: CVS Reference

### Commands And Options

This section is a reference to all CVS commands. If you are not already familiar with the syntactic conventions shared by most CVS commands, you should probably read the relevant subsections before you look up any particular command.

Node: Organization And Conventions, Next: General Patterns In CVS Commands, Up: Commands And Options

### Organization And Conventions

This section is organized alphabetically to make it easy for you to look up a particular command or option. The following conventions are used:

- Arguments to commands and options are in all-capitalized letters in the synopsis that begins each explanation. (Note: in the treeware version of the book, meta-arguments are italicized as well as capitalized; due to the limitations of standard terminal fonts, I have omitted the italicization here.)
- Optional items appear between square brackets: `[ ]`. (This works out okay because square brackets turn out not used in CVS syntaces.)
- If you must choose one from a set, the choices are separated by bars, like this: `x|y|z`. (And therefore forward slashes (`/`) should be interpreted literally - they do not divide choices in a set.)
- Plurals or ellipses indicate multiples, usually separated by whitespace. For example, FILES means one or more files, but [FILES] means zero or more files. The entry [&MOD...] means an ampersand followed immediately by a module name, then whitespace, then maybe another ampersand-module, and so on, zero or more times. (The ellipsis is used because a plural would have left it unclear whether the ampersand is needed only the first time or once for each module.)

  When a plural is parenthesized, as in FILE(S), it means that although technically there can be two or more files, usually there is only one.

- REV is often used to stand for a revision argument. This is usually either a revision number or a tag name. There are very few places in CVS where you can use one but not the other, and those places are noted in the text.

Node: General Patterns In CVS Commands, Next: Date Formats, Previous: Organization And Conventions, Up: Commands And Options

### General Patterns In CVS Commands

CVS commands follow this form:

         cvs [GLOBAL_OPTIONS] COMMAND [OPTIONS] [FILES]

The second set of options is sometimes called command options. Because there are so many of them, though, I'll just call them "options" in most places to save space.

Many commands are meant to be run within a working copy and, therefore, may be invoked without file arguments. These commands default to all of the files in the current directory and below. So when I refer to the "file" or "files" in the text, I'm talking about the files on which CVS is acting. Depending on how you invoked CVS, these files may or may not have been explicitly mentioned on the command line.

Node: Date Formats, Next: Global Options, Previous: General Patterns In CVS Commands, Up: Commands And Options

### Date Formats

Many options take a date argument. CVS accepts a wide variety of date formats - too many to list here. When in doubt, stick with the standard ISO 8601 format:

         1999-08-23

This means "23 August 1999" (in fact, "23 August 1999" is a perfectly valid date specifier too, as long as you remember to enclose it in double quotes). If you need a time of day as well, you can do this:

         "1999-08-23 21:20:30 CDT"

You can even use certain common English constructs, such as "now", "yesterday", and "12 days ago". In general, you can safely experiment with date formats; if CVS understands your format at all, it most likely will understand it in the way you intended. If it doesn't understand, it will exit with an error immediately.

Node: Global Options, Next: add, Previous: Date Formats, Up: Commands And Options

### Global Options

Here are all the global options to CVS.

### `--allow-root=REPOSITORY`

The alphabetically first global option is one that is virtually never used on the command line. The -allow-root option is used with the `pserver` command to allow authenticated access to the named repository (which is a repository top level, such as `/usr/local/newrepos`, not a project subdirectory such as `/usr/local/newrepos/myproj`).

This global option is virtually never used on the command line. Normally, the only place you'd ever use it is in /etc/inetd.conf files (see Repository Administration), which is also about the only place the `pserver` command is used.

Every repository to be accessed via `cvs pserver` on a given host needs a corresponding -allow-root option in `/etc/inetd.conf`. This is a security device, meant to ensure that people can't use a CVS pserver to gain access to private repositories.

(See The Password-Authenticating Server also the node Password Authentication Server in the Cederqvist manual.)

### `-a`

This authenticates all communications with the server. This option has no effect unless you're connecting via the GSSAPI server (gserver). GSSAPI connections are not covered in this book, because they're still somewhat rarely used (although that may change). (See the nodes Global Options and GSSAPI Authenticated in the Cederqvist manual for more information.)

### `-b` (Obsolete)

This option formerly specified the directory where the RCS binaries could be found. CVS now implements the RCS functions internally, so this option has no effect (it is kept only for backward compatibility).

### `-d` REPOSITORY

This specifies the repository, which might be an absolute pathname or a more complex expression involving a connection method, username and host, and path. If it is an expression specifying a connection method, the general syntax is:

         :METHOD:USER@HOSTNAME:PATH_TO_REPOSITORY

Here are examples using each of the connection methods:

- `:ext:jrandom@floss.red-bean.com:/usr/local/newrepos` - Connects using `rsh`, `ssh`, or some other external connection program. If the `$CVS_RSH` environment variable is unset, this defaults to `rsh`; otherwise, it uses the value of that variable.
- `:server:jrandom@floss.red-bean.com:/usr/local/newrepos` - Like `:ext:`, but uses CVS's internal implementation of rsh. (This may not be available on all platforms.)
- `:pserver:jrandom@floss.red-bean.com:/usr/local/newrepos` - Connects using the password authenticating server (see The Password-Authenticating Server in Repository Administration; see also the login command.)
- `:kserver:jrandom@floss.red-bean.com:/usr/local/newrepos` - Connects using Kerberos authentication.
- `:gserver:jrandom@floss.red-bean.com:/usr/local/newrepos` - Connects using GSSAPI authentication.
- `:fork:jrandom@floss.red-bean.com:/usr/local/newrepos` - Connects to a local repository, but using the client/server network protocol instead of directly accessing the repository files. This is useful for testing or debugging remote CVS behaviors from your local machine.
- `:local:jrandom@floss.red-bean.com:/usr/local/newrepos` - Accesses a local repository directly, as though only the absolute path to the repository had been given.

### `-e` EDITOR

Invokes EDITOR for your commit message, if the commit message was not specified on the command line with the -m option. Normally, if you don't give a message with -m, CVS invokes the editor based on the `$CVSEDITOR`, `$VISUAL`, or `$EDITOR` environment variables, which it checks in that order. Failing that, it invokes the popular Unix editor `vi`.

If you pass both the -e global option and the -m option to commit, the -e is ignored in favor of the commit message given on the command line (that way it's safe to use -e in a `.cvsrc` file).

### `-f`

This global option suppresses reading of the `.cvsrc` file.

### `--help` [COMMAND] or `-H` [COMMAND]

These two options are synonymous. If no COMMAND is specified, a basic usage message is printed to the standard output. If COMMAND is specified, a usage message for that command is printed.

### `--help-options`

Prints out a list of all global options to CVS, with brief explanations.

### `--help-synonyms`

Prints out a list of CVS commands and their short forms ("up" for "update", and so on).

### `-l`

Suppresses logging of this command in the `CVSROOT/history` file in the repository. The command is still executed normally, but no record of it is made in the history file.

### `-n`

Doesn't change any files in the working copy or in the repository. In other words, the command is executed as a "dry run" - CVS goes through most of the steps of the command but stops short of actually running it.

This is useful when you want to see what the command would have done had you actually run it. One common scenario is when you want to see what files in your working directory have been modified, but not do a full update (which would bring down changes from the repository). By running `cvs -n update`, you can see a summary of what's been done locally, without changing your working copy.

### `-q`

This tells CVS to be moderately quiet by suppressing the printing of unimportant informational messages. What is considered "important" depends on the command. For example, in updates, the messages that CVS normally prints on entering each subdirectory of the working copy are suppressed, but the one-line status messages for modified or updated files are still printed.

### `-Q`

This tells CVS to be very quiet, by suppressing all output except what is absolutely necessary to complete the command. Commands whose sole purpose is to produce some output (such as `diff` or `annotate`), of course, still give that output. However, commands that could have an effect independent of any messages that they may print (such as `update` or `commit`) print nothing.

### `-r`

Causes new working files to be created read-only (the same effect as setting the `$CVSREAD` environment variable).

If you pass this option, checkouts and updates make the files in your working copy read-only (assuming your operating system permits it). Frankly, I'm not sure why one would ever want to use this option.

### `-s` VARIABLE`=`VALUE

This sets an internal CVS variable named VARIABLE to VALUE.

On the repository side, the `CVSROOT/*info` trigger files can expand such variables to values that were assigned in the -s option. For example, if `CVSROOT/loginfo` contains a line like this

         myproj  /usr/local/bin/foo.pl ${=FISH}

and someone runs a commit from a myproj working copy like this

         floss$ cvs -s FISH=carp commit -m "fixed the bait bug"

the `foo.pl` script is invoked with `carp` as an argument. Note the funky syntax, though: The dollar sign, equal sign, and curly braces are all necessary - if any of them are missing, the expansion will not take place (at least not as intended). Variable names may contain alphanumerics and underscores only. Although it is not required that they consist entirely of capital letters, most people do seem to follow that convention.

You can use the -s flag as many times as you like in a single command. However, if the trigger script refers to variables that aren't set in a particular invocation of CVS, the command still succeeds, but none of the variables are expanded, and the user sees a warning. For example, if loginfo has this

         myproj  /usr/local/bin/foo.pl  ${=FISH}  ${=BIRD}

but the same command as before is run

         floss$ cvs -s FISH=carp commit -m "fixed the bait bug"

the person running the command sees a warning something like this (placed last in the output)

         loginfo:31: no such user variable ${=BIRD}

and the `foo.pl` script is invoked with no arguments. But if this command were run

         floss$ cvs -s FISH=carp -s BIRD=vulture commit -m "fixed the bait bug"

there would be no warning, and both `${=FISH}` and `${=BIRD}` in loginfo would be correctly expanded. In either case, the commit itself would still succeed.

Although these examples all use `commit`, variable expansion can be done with any CVS command that can be noticed in a `CVSROOT/` trigger file - which is why the -s option is global.

(See the section Repository Administrative Files later in this chapter for more details about variable expansion in trigger files.)

### `-T` DIR

Stores any temporary files in DIR instead of wherever CVS normally puts them (specifically, this overrides the value of the `$TMPDIR` environment variable, if any exists). DIR should be an absolute path.

This option is useful when you don't have write permission (and, therefore, CVS doesn't either) to the usual temporary locations.

### `-t`

Traces the execution of a CVS command. This causes CVS to print messages showing the steps that it's going through to complete a command. You may find it particularly useful in conjunction with the -n global option, to preview the effects of an unfamiliar command before running it for real. It can also be handy when you're trying to discover why a command failed.

### `-v` or `--version`

Causes CVS to print out its version and copyright information and then exit with no error.

### `-w`

Causes new working files to be created read-write (overrides any setting of the `$CVSREAD` environment variable). Because files are created read-write by default anyway, this option is rarely used.

If both -r and -w are passed, -w dominates.

### `-x`

Encrypts all communications with the server. This option has no effect unless you're connecting via the GSSAPI server (gserver). GSSAPI connections are not covered in this book, because they're still somewhat rarely used (although that may change). (See the nodes Global Options and GSSAPI Authenticated in the Cederqvist manual for more information.)

### `-z` GZIPLEVEL

Sets the compression level on communications with the server. The argument GZIPLEVEL must be a number from 1 to 9. Level 1 is minimal compression (very fast, but doesn't compress much); Level 9 is highest compression (uses a lot of CPU time, but sure does squeeze the data). Level 9 is only useful on very slow network connections. Most people find levels between 3 and 5 to be most beneficial.

A space between -z and its argument is optional.

Node: add, Next: admin, Previous: Global Options, Up: Commands And Options

### add

Synopsis: add [OPTIONS] FILES

- Alternate names - ad, new
- Requires - Working copy, repository
- Changes - Working copy

Adds a new file or files to an existing project. Although the repository is contacted for confirmation, the file does not actually appear in it until a subsequent commit is performed. (See also remove and import.)

Options:

- -kKEYWORD_SUBSTITUTION_MODE - Specifies that the file is to be stored with the given RCS keyword substitution mode. There is no space between the -k and its argument. (See the section Keyword Substitution (RCS Keywords) later in this chapter for a list of valid modes and examples.)
- -m MESSAGE - Records MESSAGE as the creation message, or description, for the file. This is different from a per-revision log message - each file has only one description. Descriptions are optional.

  As of version 1.10.7, there is a bug in CVS whereby the description is lost if you add a file via client/server CVS. The rest of the add process seems to work fine, however, if that's any comfort.

Node: admin, Next: annotate, Previous: add, Up: Commands And Options

### admin

Synopsis: admin [OPTIONS] [FILES]

- Alternate names - adm, rcs
- Requires - Working copy, repository
- Changes - Repository

This command is an interface to various administrative tasks - specifically, tasks applicable to individual RCS files in the repository, such as changing a file's keyword substitution mode or changing a log message after it's been committed.

Although admin behaves recursively if no files are given as arguments, you normally will want to name files explicitly. It's very rare for a single admin command to be meaningful when applied to all files in a project, or even in a directory. Accordingly, when the following explanations refer to the "file", they mean the file or (rarely) files passed as arguments to the admin command.

If there is a system group named `cvsadmin` on the repository machine, only members of that group can run admin (with the exception of the `cvs admin -k` command, which is always permitted). Thus you can disallow admin for all users by setting the group to have no users.

Options:

- -AOLDFILE - (Obsolete) Appends the RCS access list of OLDFILE to the access list of the file that is the argument to admin. CVS ignores RCS access lists, so this option is useless.
- -a USER1 [,USER2...] - (Obsolete) Appends the users in the comma-separated list to the access list of the file. Like -A, this option is useless in CVS.
- -bREV - Sets the revision of the file's default branch (usually the trunk) to REV. You won't normally need this option, because you can usually get the revisions you need via sticky tags, but you may use it to revert to a vendor's version if you're using vendor branches. There should be no space between the -b and its argument.
- -cCOMMENT_PREFIX - (Obsolete) Sets the comment leader of the file to COMMENT_PREFIX. The comment leader is not used by CVS or even by recent versions of RCS; therefore, this option is useless and is included only for backward-compatibility.
- -eUSER1[,USER2...] - (Obsolete) Removes the usernames appearing in the comma-separated list from the access list of the RCS file. Like -a and -A, this option is now useless in CVS.
- -i or -I - These two are so obsolete I'm not even going to tell you what they used to do. (See the Cederqvist manual if you're curious.)
- -kMODE - Sets the file's default keyword substitution mode to MODE. This option behaves like the -k option to add, only it gives you a way to change a file's mode after it's been added. (See the section Keyword Substitution (RCS Keywords) later in this chapter for valid modes.) There should be no space between -k and its argument.
- -L - Sets locking to `strict`. (See -l below.)
- -l[REV] - Locks the file's revision to REV. If REV is omitted, it locks the latest revision on the default branch (usually the trunk). If REV is a branch, it locks the latest revision on that branch.

  The intent of this option is to give you a way to do reserved checkouts, where only one user can be editing the file at a time. I'm not sure how useful this really is, but if you want to try it, you should probably do so in conjunction with the rcslock.pl script in the CVS source distribution's contrib/ directory. See comments in that file for further information. Among other things, those comments indicate that the locking must be set to `strict`. (See -L.) There is no space between -l and its argument.

- -mREV:MESSAGE - Changes the log message for revision REV to MESSAGE. Very handy - along with -k, this is probably the most frequently used admin option. There are no spaces between option and arguments or around the colon between the two arguments. Of course, MESSAGE may contain spaces within itself (in which case, remember to surround it with quotes so the shell knows it's all one thing).
- -NNAME[:[REV]] - Just like -n, except it forces the override of any existing assignment of the symbolic name NAME, instead of exiting with error.
- -nNAME[:[REV]] - This is a generic interface to assigning, renaming, and deleting tags. There is no reason, as far as I can see, to prefer it to the tag command and the various options available there (-d, -r, -b, -f, and so on). I recommend using the tag command instead. The NAME and optional REV can be combined in the following ways:
  - If only the NAME argument is given, the symbolic name (tag) named NAME is deleted.
  - If NAME: is given but no REV, NAME is assigned to the latest revision on the default branch (usually the trunk).
  - If NAME:REV is given, NAME is assigned to that revision. REV can be a symbolic name itself, in which case it is translated to a revision number first (can be a branch number).
  - If REV is a branch number and is followed by a period (`.`), NAME is attached to the highest revision on that branch. If REV is just $, NAME is attached to revision numbers found in keyword strings in the working files.

    In all cases where a NAME is assigned, CVS exits with an error if there is already a tag named NAME in the file (but see -N). There are no spaces between -n and its arguments.

- -oRANGE - Deletes the revisions specified by RANGE (also known as "outdating", hence the -o). Range can be specified in one of the following ways:
  - REV1::REV2 - Collapses all intermediate revisions between REV1 and REV2, so that the revision history goes directly from REV1 to REV2. After this, any revisions between the two no longer exist, and there will be a noncontiguous jump in the revision number sequence.
  - ::REV - Collapses all revisions between the beginning of REV's branch (which may be the beginning of the trunk) and REV, noninclusively of course. REV is then the first revision on that line.
  - REV:: - Collapses all revisions between REV and the end of its branch (which may be the trunk). REV is then the last revision on that line.
  - REV - Deletes the revision REV (-o1.8 would be equivalent to -o1.7::1.9).
  - REV1:REV2 - Deletes the revisions from REV1 to REV2, inclusive. They must be on the same branch. After this, you cannot retrieve REV1, REV2, or any of the revisions in between.
  - :REV - Deletes revisions from the beginning of the branch (or trunk) to REV, inclusive. (See the preceding warning.)
  - REV: - Deletes revisions from REV to the end of its branch (or trunk), inclusive. (See the preceding warning.)

    None of the revisions being deleted may have branches or locks. If any of the revisions have symbolic names attached, you have to delete them first with tag -d or admin -n. (Actually, right now CVS only protects against deleting symbolically named revisions if you're using one of the :: syntaxes, but the single-colon syntaxes may soon change to this behavior as well.)

    Instead of using this option to undo a bad commit, you should commit a new revision that undoes the bad change. There are no spaces between -o and its arguments.

- -q - Tells CVS to run quietly - don't print diagnostic messages (just like the global -q option).
- -sSTATE[:REV] - Sets the state attribute of revision REV to STATE. If REV is omitted, the latest revision on the default branch (usually the trunk) is used. If REV is a branch tag or number, the latest revision on that branch is used.

  Any string of letters or numbers is acceptable for STATE; some commonly used states are Exp for experimental, Stab for stable, and Rel for released. (In fact, CVS sets the state to Exp when a file is created.) Note that CVS uses the state dead for its own purposes, so don't specify that one.

  States are displayed in cvs log output, and in the $Log and $State RCS keywords in files. There is no space between -s and its arguments.

- -t[DESCFILE] - Replaces the description (creation message) for the file with the contents of DESCFILE, or reads from standard input if no DESCFILE is specified.

  This useful option, unfortunately, does not currently work in client/server CVS. In addition, if you try it in client/server and omit DESCFILE, any existing description for the file is wiped out and replaced with the empty string. If you need to rewrite a file's description, either do so using only local CVS on the same machine as the repository or -t-STRING (see below). There is no space between -t and its argument. DESCFILE may not begin with a hyphen (`-`).

- -t-STRING - Like -t, except that STRING is taken directly as the new description. STRING may contain spaces, in which case you should surround it with quotes. Unlike the other syntax for -t, this works in client/server as well as locally.
- -U - Sets locking to nonstrict. (See -l and -L options, discussed earlier.)
- -u[REV] - Unlocks revision REV. (See -l.) If REV is omitted, CVS unlocks the latest lock held by the caller. If REV is a branch, CVS unlocks the latest revision on that branch. If someone other than the owner of a lock breaks the lock, a mail message is sent to the original locker. The content for this message is solicited on standard input from the person breaking the lock. There is no space between -u and its argument.
- -VRCS_VERSION_NUMBER - (Obsolete) This used to be a way to tell CVS to produce RCS files acceptable to previous versions of RCS. Now the RCS format used by CVS is drifting away from the RCS format used by RCS, so this option is useless. Specifying it results in an error.
- -xSUFFIX - (Obsolete) Theoretically, this gives you a way to specify the suffix for RCS file names. However, CVS and related tools all depend on that suffix being the default (,v), so this option does nothing.

Node: annotate, Next: checkout, Previous: admin, Up: Commands And Options

### annotate

Synopsis: annotate [OPTIONS] [FILES]

- Alternate name - ann
- Requires - Working copy, repository
- Changes - Nothing

Shows information on who last modified each line of each file and when. Each line of output corresponds to one line of the file. From left to right, the line displays the revision number of the last modification of that line, a parenthetical expression containing the user and date of the modification, a colon, and the contents of the line in the file.

For example, if a file looks like this

         this is a test file
         it only has too lines
         I mean "two"

the annotations for that file could look like this

         1.1          (jrandom  22-Aug-99): this is a test file
         1.1          (jrandom  22-Aug-99): it only has too lines
         1.2          (jrandom  22-Aug-99): I mean "two"

from which you would know that the first two lines were in the initial revision, and the last line was added or modified (also by jrandom) in Revision 1.2.

Options:

- -D DATE - Shows the annotations as of the latest revision no later than DATE.
- -f - Forces use of the head revision if the specified tag or date is not found. You can use this in combination with -D or -r to ensure that there is some output from the annotate command, even if only to show Revision 1.1 of the file.
- -l - Local. Runs in the current working directory only. Does not descend into subdirectories.
- -R - Recursive. Descends into subdirectories (the default). The point of the -R option is to override any -l option set in a .cvsrc file.
- -r REV - Shows annotations as of revision REV (can be a revision number or a tag).

Node: checkout, Next: commit, Previous: annotate, Up: Commands And Options

### checkout

Synopsis: checkout [OPTIONS] PROJECT(S)

- Alternate names - co, get
- Requires - Repository
- Changes - Current directory

Checks out a module from the repository into a working copy. The working copy is created if it doesn't exist already and updated if it does. (See also update.)

Options:

- -A - Resets any sticky tags, sticky dates, or sticky -k (RCS keyword substitution mode) options. This is like the -A option to update and is probably more often used there than with checkout.
- -c - Doesn't check anything out; just prints the CVSROOT/modules file, sorted, on standard output. This is a good way to get an overview of what projects are in a repository. However, a project without an entry in modules does not appear (this situation is quite normal because the name of the project's top-level directory in the repository functions as the project's "default" module name).
- -D DATE - Checks out the latest revisions no later than DATE. This option is sticky, so you won't be able to commit from the working copy without resetting the sticky date. (See -A.) This option also implies -P, described later.
- -d DIR - Creates the working copy in a directory named DIR, instead of creating a directory with the same name as the checked-out module. If you check out only a portion of a project and the portion is located somewhere beneath the project's top level, the locally empty intermediate directories are omitted. You can use -N to suppress this directory-collapsing behavior.
- -f - Forces checkout of the head revision if the specified tag or date is not found. Most often used in combination with -D or -r to ensure that something always gets checked out.
- -j REV[:DATE] or -j REV1[:DATE] -j REV2[:DATE] - Joins (merges) two lines of development. This is just like the -j option to update, where it is more commonly used. (See update for details.)
- -k MODE - Substitutes RCS keywords according to MODE (which can override the default modes for the files). (See the section Keyword Substitution (RCS Keywords) later in this chapter for valid modes.) The mode chosen will be sticky - future updates of the working copy will keep that mode.
- -l - Local. Checks out the top-level directory of the project only. Does not process subdirectories.
- -N - Suppresses collapsing of empty directories with -d option. (See -d.)
- -n - Doesn't run any checkout program that was specified with -o in CVSROOT/modules. (See the section Repository Administrative Files later in this chapter for more on this.)
- -P - Prunes empty directories from the working copy (like the -P option to update).
- -p - Checks files out to standard output, not into files (like the -p option to update).
- -R - Checks out subdirectories as well (the default). (See also the -f option.)
- -r TAG - Checks out the project as of revision TAG (it would make almost no sense to specify a numeric revision for TAG, although CVS lets you). This option is sticky and implies -P.
- -s - Like -c, but shows the status of each module and sorts by status. (See modules in the section Repository Administrative Files for more information.)

Node: commit, Next: diff, Previous: checkout, Up: Commands And Options

### commit

Synopsis: commit [OPTIONS] [FILES]

- Alternate names - ci, com
- Requires - Working copy, repository
- Changes - Repository (and working copy administrative area)

Commits changes from a working copy to the repository.

Options:

- -F MSGFILE - Uses the contents of MSGFILE for the log message instead of invoking an editor. This option cannot be combined with -m.
- -f - Forces commit of a new revision even if no changes have been made to the files. `commit` does not recurse with this option (it implies -l). You can force it to recurse with -R.

  This meaning of -f is at odds with its usual meaning ("force to head revision") in CVS commands.

- -l - Local. Commits changes from the current directory only. Doesn't descend into subdirectories.
- -m MESSAGE - Uses MESSAGE as the log message instead of invoking an editor. Cannot be used with -F.
- -n - Does not run any module program. (See the section Repository Administrative Files in this chapter for information about module programs.)
- -R - Commits changes from subdirectories as well as from the current directory (the default). This option is used only to counteract the effect of a -l in .cvsrc.
- -r REV - Commits to revision REV, which must be either a branch or a revision on the trunk that is higher than any existing revision. Commits to a branch always go on the tip of the branch (extending it); you cannot commit to a specific revision on a branch. Use of this option sets the new revision as a sticky tag on the file. This can be cleared with update -A.

  The -r REV option implies -f as well. A new revision is committed even if there are no changes to commit.

Node: diff, Next: edit, Previous: commit, Up: Commands And Options

### diff

Synopsis: diff [OPTIONS] [FILES]

- Alternate names - di, dif
- Requires - Working copy, repository
- Changes - Nothing

Shows the difference between two revisions (in Unix diff format). When invoked with no options, CVS diffs the repository base revisions against the (possibly uncommitted) contents of the working copy. The base revisions are the latest revisions of this working copy retrieved from the repository; note that there could be even later revisions in the repository, if someone else committed changes but this working copy hasn't been updated yet. (See also rdiff.)

Options:

- -D DATE - Diffs against the latest revisions no later than DATE. Behaves like -r REV, except uses dates rather than revisions. (See -r for details.)
- -k MODE - Expands RCS keywords in the diffs according to MODE. (See the section Keyword Substitution (RCS Keywords) in this chapter for possible modes.)
- -l - Local. If no files were specified as arguments, this option diffs files in the current directory, but does not descend into subdirectories.
- -R - Recursive. This option is the opposite of -l. This is the default behavior, so the only reason to specify -R is to counteract a -l in a .cvsrc file.
- -r REV or -r REV1 -r REV2 - Diffs against (or between) the specified revisions. With one -r option, this diffs revision REV against your working copy of that file (so when multiple files are being diffed, REV is almost always a tag). With two -r options, it diffs REV1 against REV2 for each file (and the working copy is, therefore, irrelevant). The two revisions can be in any order - REV1 does not have to be an earlier revision than REV2. The output reflects the direction of change. With no -r options, it shows the difference between the working file and the revision on which it is based.

Diff Compatibility Options

In addition to the preceding options, cvs diff also shares a number of options with the GNU version of the standard command-line diff program. Following is a complete list of these options, along with an explanation of a few of the most commonly used ones. (See the GNU diff documentation for the others.)

         -0 -1 -2 -3 -4 -5 -6 -7 -8 -9
             --binary
             --brief
             --changed-group-format=ARG
             -c
               -C NLINES
               --context[=LINES]
             -e --ed
             -t --expand-tabs
             -f --forward-ed
             --horizon-lines=ARG
             --ifdef=ARG
             -w --ignore-all-space
             -B --ignore-blank-lines
             -i --ignore-case
             -I REGEXP
                --ignore-matching-lines=REGEXP
             -h
             -b --ignore-space-change
             -T --initial-tab
             -L LABEL
               --label=LABEL
             --left-column
             -d --minimal
             -N --new-file
             --new-line-format=ARG
             --old-line-format=ARG
             --paginate
             -n --rcs
             -s --report-identical-files
             -p
             --show-c-function
             -y --side-by-side
             -F REGEXP
             --show-function-line=REGEXP
             -H --speed-large-files
             --suppress-common-lines
             -a --text
             --unchanged-group-format=ARG
             -u
               -U NLINES
               --unified[=LINES]
             -V ARG
             -W COLUMNS
               --width=COLUMNS

Following are the GNU diff options most frequently used with cvs diff.

- -B - Ignores differences that are merely the insertion or deletion of blank lines (lines containing nothing but whitespace characters).
- -b - Ignores differences in the amount of whitespace. This option treats all whitespace sequences as being equal and ignores whitespace at line end. More technically, this option collapses each whitespace sequence in the input to a single space and removes any trailing whitespace from each line, before taking the diff. (See also -w.)
- -c - Shows output in context diff format, defaulting to three lines of context per difference (for the sake of the patch program, which requires at least two lines of context).
- -C NUM - context=NUM - Like -c, but with NUM lines of context.
- -i - Compares case insensitively. Treats upper- and lowercase versions of a letter as the same.
- -u - Shows output in unified diff format.
- -w - Ignores all whitespace differences, even when one side of the input has whitespace where the other has none. Essentially a stronger version of -b.

Node: edit, Next: editors, Previous: diff, Up: Commands And Options

### edit

Synopsis: edit [OPTIONS] [FILES]

- Alternate names - None
- Requires - Working copy, repository
- Changes - Permissions in working copy, watchlist in repository

Signals that you are about to begin editing a watched file or files. Also adds you as a temporary watcher to the file's watch list (you'll be removed when you do cvs unedit). (See also watch, watchers, unedit, and editors.)

Options:

- -a ACTIONS - Specifies for which actions you want to be a temporary watcher. ACTIONS should be either edit, unedit, commit, all, or none. (If you don't use -a, the temporary watch will be for all actions.)
- -l - Local. Signals editing for files in the current working directory only.
- -R - Recursive (this is the default). Opposite of b; you would only need to pass -R to counteract a -l in a .cvsrc file.

Node: editors, Next: export, Previous: edit, Up: Commands And Options

### editors

Synopsis: editors [OPTIONS] [FILES]

- Alternate names - None
- Requires - Working copy, repository
- Changes - Nothing

Shows who is currently editing a watched file. (See also watch, watchers, edit, and unedit.)

Options:

- -l - Local. Views editors for files in current directory only.
- -R - Recursive. Views editors for files in this directory and its subdirectories (the default). You may need to pass -R to counteract a -l in a .cvsrc file, though.

Node: export, Next: gserver, Previous: editors, Up: Commands And Options

### export

Synopsis: export [OPTIONS] PROJECT(S)

- Alternate names - exp, ex
- Requires - Repository
- Changes - Current directory

Exports files from the repository to create a project tree that is not a working copy (has no CVS/ administrative subdirectories). Useful mainly for packaging distributions.

Options:

- -D DATE - Exports the latest revisions no later than DATE.
- -d DIR - Exports into DIR (otherwise, defaults to the module name).
- -f - Forces use of head revisions, if a given tag or date would result in nothing being found (for use with -D or -r).
- -k MODE - Expands RCS keywords according to MODE. (See the section Keyword Substitution (RCS Keywords) later in this chapter.)
- -l - Local. Exports only the top level of the project, no subdirectories.
- -N - Doesn't "collapse" empty intermediate directories. This option is like the -N option to checkout (see checkout).
- -n - Does not run a module program as may be specified in `CVSROOT/modules`. (See Repository Administrative Files later in this chapter for more about this.)
- -P - Prunes empty directories (like the -P option to checkout or update).
- -R - Recursive. Exports all subdirectories of the project (the default). The only reason to specify -R is to counteract a -l in a `.cvsrc` file.
- -r REV - Exports revision REV. REV is almost certainly a tag name, not a numeric revision.

Node: gserver, Next: history, Previous: export, Up: Commands And Options

### gserver

Synopsis: gserver

This is the GSSAPI (Generic Security Services API) server. This command is not normally run directly by users. Instead, it is started up on the server side when a user connects from a client with the `:gserver:` access method:

         cvs -d :gserver:floss.red-bean.com:/usr/local/newrepos checkout myproj

GSSAPI provides, among other things, Kerberos Version 5; for Kerberos Version 4, use `:kserver:`.

Setting up and using a GSSAPI library on your machines is beyond the scope of this book. (See the node GSSAPI Authenticated in the Cederqvist manual for some useful hints, however.)

Options: None.

Node: history, Next: import, Previous: gserver, Up: Commands And Options

### history

Synopsis: history [OPTIONS] [FILENAME_SUBSTRING(S)]

- Alternate names - hi, his
- Requires - Repository, CVSROOT/history
- Changes - Nothing

Shows a history of activity in the repository. Specifically, this option shows records of checkouts, commits, rtags, updates, and releases. By default, the option shows checkouts (but see the -x option). This command won't work if there's no CVSROOT/history file in the repository.

The history command differs from other CVS commands in several ways. First, it must usually be given options to do anything useful (and some of those options mean different things for history than they do elsewhere in CVS). Second, instead of taking full file names as arguments, it takes one or more substrings to match against file names (all records matching at least one of those substrings are retrieved). Third, history's output looks a lot like line noise until you learn to read it, so I'll explain the output format in a special section, after the options. (See also log.)

Options:

- -a - Shows history for all users (otherwise, defaults to self).
- -b STR - Shows data back to record containing string STR in the module name, file name, or repository path.
- -c - Reports commits.
- -D DATE - Shows data since DATE (the usual CVS date formats are available).
- -e - Everything - reports on all record types.
- -f FILE - Reports the most recent event concerning FILE. You can specify this option multiple times. This is different from the usual meaning of -f in CVS commands: "Force to head revision as a last resort."
- -l - Shows the record representing the last (as in "most recent") event of each project. This is different from the usual meaning of -l in CVS commands: "Run locally, do not recurse."
- -m MODULE - This provides a full report about MODULE (a project name). You can specify this option multiple times.
- -n MODULE - Reports the most recent event about MODULE. For example, checking out the module is about the module itself, but modifying or updating a file inside the module is about that file, not about the module. You can specify this option multiple times. This is different from the usual meaning of -n in CVS commands: "Don't run a CVSROOT/modules program."
- -o - Shows checkout records (the default).
- -p REPOS - Shows data for a particular directory in the repository. You can specify this option multiple times. The meaning of this option differs from the usual meaning of -p in CVS commands: "Pipe the data to standard output instead of a file."

  This option appears to be at least partially broken as of summer 1999.

- -r REV - Shows records referring to revisions since the revision or tag named REV appears in individual RCS files. Each RCS file is searched for the revision or tag.
- -T - Reports on all tag events.
- -t TAG - Shows records since tag TAG was last added to the history file. This differs from the -r flag in that it reads only the CVSROOT/history file, not the RCS files, and is therefore much faster.
- -u USER - Shows events associated with USER. You can specify this option multiple times.
- -w - Shows records that are associated with the same working directory from which you are invoking history.
- -X HISTORYFILE - Uses HISTORYFILE instead of CVSROOT/history. This option is mainly for debugging and is not officially supported; nevertheless, you may find it useful (perhaps for generating human-readable reports from old history files you've kept around).
- -x TYPES - Reports on events specified in TYPES. Each type is represented by a single letter, from the set `TOEFWUCGMAR`; any number of letters can be combined. Here is what they mean:
  - T - Tag
  - O - Checkout
  - E - Export
  - F - Release
  - W - Update (newly obsolete file removed from working copy)
  - U - Update (file was checked out over user file)
  - C - Update (merge, with conflicts)
  - G - Update (merge, no conflicts)
  - M - Commit (file was modified)
  - A - Commit (file was added)
  - R - Commit (file was removed)

  The default, if no -x option is given, is to show checkouts (like `-x O`).

- -z ZONE - Displays times in output as for time zone ZONE. ZONE is an abbreviated time zone name, such as UTC, GMT, BST, CDT, CCT, and so on. A complete list of time zones is available in the TimezoneTable in the file lib/getdate.c in the CVS source distribution.

History Output

The output of the history command is a series of lines; each line represents one "history event" and starts with a single code letter indicating what type of event it is. For example:

         floss$ cvs history -D yesterday -x TMO
         M 08/21 20:19 +0000 jrandom 2.2              baar       myproj == <remote>
         M 08/22 04:18 +0000 jrandom 1.2              README     myproj == <remote>
         O 08/22 05:15 +0000 jrandom myproj =myproj= ~/src/*
         M 08/22 05:33 +0000 jrandom 2.18             README.txt myproj == ~/src/myproj
         O 08/22 14:25 CDT jrandom myproj =myproj= ~/src/*
         O 08/22 14:26 CDT jrandom [99.08.23.19.26.03] myproj =myproj= ~/src/*
         O 08/22 14:28 CDT jrandom [Exotic_Greetings-branch] myproj =myproj= ~/src/*

The code letters are the same as for the -x option just described. Following the code letter is the date of the event (expressed in UTC/GMT time, unless the -z option is used), followed by the user responsible for the event.

After the user might be a revision number, tag, or date, but only if such is appropriate for the event (date or tag will be in square brackets and formatted as shown in the preceding example). If you commit a file, it shows the new revision number; if you check out with -D or -r, the sticky date or tag is shown in square brackets. For a plain checkout, nothing extra is shown.

Next comes the name of the file in question, or module name if the event is about a module. If the former, the next two things are the module/project name and the location of the working copy in the user's home directory. If the latter, the next two things are the name of the module's checked-out working copy (between two equal signs), followed by its location in the user's home directory. (The name of the checked-out working copy may differ from the module name if the -d flag is used with checkout.)

Node: import, Next: init, Previous: history, Up: Commands And Options

### import

Synopsis: import [OPTIONS] REPOSITORY VENDOR_TAG RELEASE_TAG(S)

- Alternate names - im, imp
- Requires - Repository, current directory (the source directory)
- Changes - Repository

Imports new sources into the repository, either creating a new project or creating a new vendor revision on a vendor branch of an existing project. (See Advanced CVS for a basic explanation of vendor branches in import, which will help you to understand the following.)

It's normal to use import to add many files or directories at once or to create a new project. To add single files, you should use add.

Options:

- -b BRANCH - Imports to vendor branch BRANCH. (BRANCH is an actual branch number, not a tag.) This is rarely used but can be helpful if you get sources for the same project from different vendors. A normal import command assumes that the sources are to be imported on the default vendor branch, which is "1.1.1". Because it is the default, you normally don't bother to specify it with -b:

                floss$ cvs import -m "importing from vendor 1" theirproj THEM1 THEM1-0

  To import to a vendor branch other than the default, you must specify a different branch number explicitly:

                floss$ cvs import -b 1.1.3 -m "from vendor 2" theirproj THEM2 THEM2-0

  The 1.1.3 branch can absorb future imports and be merged like any other vendor branch. However, you must make sure any future imports that specify `-b 1.1.3` also use the same vendor tag (`THEM2`). CVS does not check to make sure that the vendor branch matches the vendor tag. However, if they mismatch, odd and unpredictable things will happen.

  Vendor branches are odd-numbered, the opposite of regular branches.

- -d - Takes the file's modification time as the time of import instead of using the current time. This does not work with client/server CVS.
- -I NAME - Gives file names that should be ignored in the import. You can use this option multiple times in one import. Wildcard patterns are supported: `*.foo` means ignore everything ending in `.foo`. (See cvsignore in Repository Administrative Files for details about wildcards.)

  The following file and directory names are ignored by default:

                	.
                	..
                	.#*
                	#*
                	,*
                	_$*
                	*~
                	*$
                	*.a
                	*.bak
                	*.BAK
                	*.elc
                	*.exe
                	*.ln
                	*.o
                	*.obj
                	*.olb
                	*.old
                	*.orig
                	*.rej
                	*.so
                	*.Z
                	.del-*
                	.make.state
                	.nse_depinfo
                	core
                	CVS
                	CVS.adm
                	cvslog.*
                	RCS
                	RCSLOG
                	SCCS
                	tags
                	TAGS

  You can suppress the ignoring of those file name patterns, as well as any specified in `.cvsignore`, `CVSROOT/cvsignore`, and the `$CVSIGNORE` environment variable, by using `-I !`. That is,

                floss$ cvs import -I ! -m "importing the universe" proj VENDOR VENDOR_0

  imports all files in the current directory tree, even those that would otherwise be ignored.

  Using a `-I !` clears whatever ignore list has been created to that point, so any -I options that came before it would be nullified, but any that come after will still count. Thus,

                floss$ cvs import -I ! -I README.txt -m "some msg" theirproj THEM THEM_0

  is not the same as

                floss$ cvs import -I README.txt -I ! -m "some msg" theirproj THEM THEM_0

  The former ignores (fails to import) README.txt, whereas the latter imports it.

- -k MODE - Sets the default RCS keyword substitution mode for the imported files. (See Keyword Substitution (RCS Keywords) later in this chapter for a list of valid modes.)
- -m MESSAGE - Records MESSAGE as the import log message.
- -W SPEC - Specifies filters based on file names that should be in effect for the import. You can use this option multiple times. (See cvswrappers in Repository Administrative Files for details about wrapper specs.)

Node: init, Next: kserver, Previous: import, Up: Commands And Options

### init

Synopsis: init NEW_REPOSITORY

- Alternate names - None
- Requires - Location for new repository
- Creates - Repository

Creates a new repository (that is, a root repository in which many different projects are stored). You will almost always want to use the global -d option with this, as in

         floss$ cvs -d /usr/local/yet_another_repository init

because even if you have a CVSROOT environment variable set, it's probably pointing to an existing repository, which would be useless and possibly dangerous in the context of this command. (See Repository Administration for additional steps that you should take after initializing a new repository.)

Options: None.

Node: kserver, Next: log, Previous: init, Up: Commands And Options

### kserver

Synopsis: kserver

This is the Kerberos server. (If you have Kerberos libraries Version 4 or below - Version 5 just uses GSSAPI, see gserver.) This command is not normally run directly by users but is instead started up on the server side when a user connects from a client with the `:kserver:` access method:

         cvs -d :kserver:floss.red-bean.com:/usr/local/newrepos checkout myproj

Setting up and using Kerberos on your machine is beyond the scope of this book. (However, see the node Kerberos Authenticated in the Cederqvist manual for some useful hints.)

Options: None.

Node: log, Next: login, Previous: kserver, Up: Commands And Options

### log

Synopsis: log [OPTIONS] [FILES]

- Alternate names - lo, rlog
- Requires - Working copy, repository
- Changes - Nothing

Shows log messages for a project, or for files within a project. The output of log is not quite in the same style as the output of other CVS commands, because log is based on an older RCS program (rlog). Its output format gives a header, containing various pieces of non-revision-specific information about the file, followed by the log messages (arranged by revision). Each revision shows not merely the revision number and log message, but also the author and date of the change and the number of lines added or deleted. All times are printed in UTC (GMT), not local time.

Because log output is per file, a single commit involving multiple files may not immediately appear as a conceptually atomic change. However, if you read all of the log messages and dates carefully, you may be able to reconstruct what happened. (For information about a tool that can reformat multifile log output into a more readable form, see cvs2cl - Generate GNU-Style ChangeLogs in Third-Party Tools for details.) (See also history.)

Options:

As you read over the following filtering options, it may not be completely clear how they behave when combined. A precise description of log's behavior is that it takes the intersection of the revisions selected by -d, -s, and -w, intersected with the union of those selected by -b and -r.

- -b - Prints log information about the default branch only (usually the highest branch on the trunk). This is usually done to avoid printing the log messages for side branches of development.
- -dDATES - Prints log information for only those revisions that match the date or date range given in DATES, a semicolon-separated list. Dates can be given in any of the usual date formats (see Date Formats earlier in this section) and can be combined into ranges as follows:
  - DATE1<DATE2 - Selects revisions created between DATE1 and DATE2. If DATE1 is after DATE2, use `>` instead; otherwise, no log messages are retrieved.
  - <DATE DATE> - All revisions from DATE or earlier.
  - >DATE DATE< - All revisions from DATE or later.
  - DATE - Just selects the most recent single revision from DATE or earlier.

  You may use `<=` and `>=` instead of `<` and `>` to indicate an inclusive range (otherwise, ranges are exclusive). Multiple ranges should be separated with semicolons, for example

                floss$ cvs log -d"1999-06-01<1999-07-01;1999-08-01<1999-09-01"

  selects log messages for revisions committed in June or August of 1999 (skipping July). There can be no space between -d and its arguments.

- -h - Prints only the header information for each file, which includes the file name, working directory, head revision, default branch, access list, locks, symbolic names (tags), and the file's default keyword substitution mode. No log messages are printed.
- -l - Local. Runs only on files in the current working directory.
- -N - Omits the list of symbolic names (tags) from the header. This can be helpful when your project has a lot of tags but you're only interested in seeing the log messages.
- -R - Prints the name of the RCS file in the repository.

  This is different from the usual meaning of -R: "recursive". There's no way to override a -l for this command, so don't put log -l in your .cvsrc.

- -rREVS - Shows log information for the revisions specified in REVS, a comma-separated list. REVS can contain both revision numbers and tags. Ranges can be specified like this:
  - REV1:REV2 - Revisions from REV1 to REV2 (they must be on the same branch).
  - :REV - Revisions from the start of REV's branch up to and including REV.
  - REV: - Revisions from REV to the end of REV's branch.
  - BRANCH - All revisions on that branch, from root to tip.
  - BRANCH1:BRANCH2 - A range of branches - all revisions on all the branches in that range.
  - BRANCH. - The latest (tip) revision on BRANCH.

  Finally, a lone -r, with no argument, means select the latest revision on the default branch (normally the trunk). There can be no space between -r and its argument.

  If the argument to -r is a list, it is comma-separated, not semicolon-separated like -d.

- -sSTATES - Selects revisions whose state attribute matches one of the states given in STATES, a comma-separated list. There can be no space between -s and its argument.

  If the argument to -s is a list, it is comma-separated, not semicolon-separated like -d.

- -t - Like -h, but also includes the file's description (its creation message).
- -wUSERS - Selects revisions committed by users whose usernames appear in the comma-separated list USERS. A lone -w with no USERS means to take the username of the person running cvs log.

  Remember that when user aliasing is in effect (see the section The Password-Authenticating Server in Repository Administration), CVS records the CVS username, not the system username, with each commit. There can be no space between -w and its argument.

  If the argument to -w is a list, it is comma-separated, not semicolon-separated like -d.

Node: login, Next: logout, Previous: log, Up: Commands And Options

### login

Synopsis: login

- Alternate names - logon, lgn
- Requires - Repository
- Changes - ~/.cvspass file

Contacts a CVS server and confirms authentication information for a particular repository. This command does not affect either the working copy or the repository; it just confirms a password (for use with the :pserver: access method) with a repository and stores the password for later use in the .cvspass file in your home directory. Future commands accessing the same repository with the same username will not require you to rerun login, because the client-side CVS will just consult the .cvspass file for the password.

If you use this command, you should specify a repository using the pserver access method, like this

         floss$ cvs -d :pserver:jrandom@floss.red-bean.com:/usr/local/newrepos

or by setting the CVSROOT environment variable.

If the password changes on the server side, you have to rerun login.

Options: None.

Node: logout, Next: pserver, Previous: login, Up: Commands And Options

### logout

Synopsis: logout

- Alternate names - None
- Requires - ~/.cvspass file
- Changes - ~/.cvspass file

The opposite of login - removes the password for this repository from .cvspass.

Options: None.

Node: pserver, Next: rdiff, Previous: logout, Up: Commands And Options

### pserver

Synopsis: pserver

- Alternate names - None
- Requires - Repository
- Changes - Nothing

This is the password-authenticating server. This command is not normally run directly by users but is started up from `/etc/inetd.conf` on the server side when a user connects from a client with the `:pserver:` access method. (See also the login and logout commands, and the file `.cvspass` in the Run Control Files section in this chapter. See Repository Administration for details on setting up a password-authenticating CVS server.)

Options: None.

Node: rdiff, Next: release, Previous: pserver, Up: Commands And Options

### rdiff

Synopsis: rdiff [OPTIONS] PROJECTS

- Alternate names - patch, pa
- Requires - Repository
- Changes - Nothing

Like the diff command, except it operates directly in the repository and, therefore, requires no working copy. This command is meant for obtaining the differences between one release and another of your project, in a format suitable as input to the patch program (perhaps so you can distribute patch files to users who want to upgrade).

The operation of the patch program is beyond the scope of this book. However, note that if the patch file contains diffs for files in subdirectories, you may need to use the -p option to patch to get it to apply the differences correctly. (See the patch documentation for more about this.) (See also diff.)

Options:

- -c - Prints output in context diff format (the default).
- -D DATE or -D DATE1 -D DATE2 - With one date, this shows the differences between the files as of DATE and the head revisions. With two dates, it shows the differences between the dates.
- -f - Forces the use of head revision if no matching revision is found for the -D or -r flag (otherwise, rdiff would just ignore the file).
- -l - Local. Won't descend into subdirectories.
- -R - Recursive. Descends into subdirectories (the default). You only specify this option to counteract a -l in your .cvsrc.
- -r REV -r REV1 -r REV2 - With one revision, this shows the differences between revision REV of the files and the head revisions. With two, it shows the differences between the revisions.
- -s - Displays a summary of differences. This shows which files have been added, modified, or removed, without showing changes in their content. The output looks like this:

                floss$ cvs -Q rdiff -s -D 1999-08-20 myproj
                File myproj/Random.txt is new; current revision 1.4
                File myproj/README.txt changed from revision 2.1 to 2.20
                File myproj/baar is new; current revision 2.3

- -t - Shows the diff between the top two revisions of each file. This is a handy shortcut for determining the most recent changes to a project. This option is incompatible with -D and -r.
- -u - Prints output in unidiff format. Older versions of patch can't handle unidiff format; therefore, don't use -u if you're trying to generate a distributable patch file - use -c instead.
- -V (Obsolete) - CVS reports an error if you try to use this option now. I've included it here only in case you see some old script trying to use it.

Node: release, Next: remove, Previous: rdiff, Up: Commands And Options

### release

Synopsis: release [OPTIONS] DIRECTORY

- Alternate names - re, rel
- Requires - Working copy
- Changes - Working copy, CVSROOT/history

Cancels a checkout (indicates that a working copy is no longer in use). Unlike most CVS commands that operate on a working copy, this one is not invoked from within the working copy but from directly above it (in its parent directory). You either have to set your CVSROOT environment variable or use the -d global option, as CVS will not be able to find out the repository from the working copy.

Using release is never necessary. Because CVS doesn't normally do locking, you can just remove your working copy.

However, if you have uncommitted changes in your working copy or you want your cessation of work to be noted in the CVSROOT/history file (see the history command), you should use release. CVS first checks for any uncommitted changes; if there are any, it warns you and prompts for continuation. Once the working copy is actually released, that fact is recorded in the repository's CVSROOT/history file.

Options:

- -d - Deletes the working copy if the release succeeds. Without -d, the working copy remains on disk after the release.

If you created any new directories inside your working copy but did not add them to the repository, they are deleted along with the rest of the working copy, if you specified the -d flag.

Node: remove, Next: rtag, Previous: release, Up: Commands And Options

### remove

Synopsis: remove [OPTIONS] [FILES]

- Alternate names - rm, delete
- Requires - Working copy
- Changes - Working copy

Removes a file from a project. Normally, the file itself is removed from disk when you invoke this command (but see -f). Although this command operates recursively by default, it is common to explicitly name the files being removed. Note the odd implication of the previous sentence: Usually, you run cvs remove on files that don't exist anymore in your working copy.

Although the repository is contacted for confirmation, the file is not actually removed until a subsequent commit is performed. Even then, the RCS file is not really removed from the repository; if it is removed from the trunk, it is just moved into an Attic/ subdirectory, where it is still available to exist on branches. If it is removed from a branch, its location is not changed, but a new revision with state dead is added on the branch. (See also add.)

Options:

- -f - Force. Deletes the file from disk before removing it from CVS. This meaning differs from the usual meaning of -f in CVS commands: "Force to head revision".
- -l - Local. Runs only in current working directory.
- -R - Recursive. Descends into subdirectories (the default). This option exists only to counteract a -l in .cvsrc.

Node: rtag, Next: server, Previous: remove, Up: Commands And Options

### rtag

Synopsis: rtag [OPTIONS] TAG PROJECT(S)

- Alternate names - rt, rfreeze
- Requires - Repository
- Changes - Repository

Tags a module directly in the repository (requires no working copy). You probably need to have your CVSROOT environment variable set or use the -d global option for this to work. (See also tag.)

Options:

- -a - Clears the tag from any removed files, because removed files stay in the repository for historical purposes but are not considered part of the live project anymore. Although it's illegal to tag files with a tag name that's already in use, there should be no interference if the name is only used in removed files (which, from the current point of view of the project, don't exist anymore).
- -b - Creates a new branch, with branch name TAG.
- -D DATE - Tags the latest revisions no later than DATE.
- -d - Deletes the tag. No record is made of this change - the tag simply disappears. CVS does not keep a change history for tags.
- -F - Forces reassignment of the tag name, if it happens to exist already for some other revision in the file.
- -f - Forces to head revision if a given tag or date is not found. (See -r and -D.)
- -l - Local. Runs in the current directory only.
- -n - Won't execute a tag program from CVSROOT/modules. (See the section Repository Administrative Files later in this chapter for details about such programs.)
- -R - Recursive. Descends into subdirectories (the default). The -R option exists only to counteract a -l in .cvsrc.
- -r REV - Tags revision REV (which may itself be a tag name).

Node: server, Next: status, Previous: rtag, Up: Commands And Options

### server

Synopsis: server

Starts up a CVS server. This command is never invoked by users (unless they're trying to debug the client/server protocol), so forget I even mentioned it.

Options: None.

Node: status, Next: tag, Previous: server, Up: Commands And Options

### status

Synopsis: status [OPTIONS] [FILES]

- Alternate names - st, stat
- Requires - Working copy
- Changes - Nothing

Shows the status of files in the working copy.

Options:

- -l - Local. Runs in the current directory only.
- -R - Recursive. Descends into subdirectories (the default). The -R option exists only to counteract a -l in .cvsrc.
- -v - Shows tag information for the file.

Node: tag, Next: unedit, Previous: status, Up: Commands And Options

### tag

Synopsis: tag [OPTIONS] TAG [FILES]

- Alternate names - ta, freeze
- Requires - Working copy, repository
- Changes - Repository

Attaches a name to a particular revision or collection of revisions for a project. Often called "taking a snapshot" of the project. This command is also used to create branches in CVS. (See the -b option - see also rtag.)

Options:

- -b - Creates a branch named TAG.
- -c - Checks that the working copy has no uncommitted changes. If it does, the command exits with a warning, and no tag is made.
- -D DATE - Tags the latest revisions no later than DATE.
- -d - Deletes the tag. No record is made of this change; the tag simply disappears. CVS does not keep a change history for tags.
- -F - Forces reassignment of the tag name, if it happens to exist already for some other revision in the file.
- -f - Forces to head revision if a given tag or date is not found. (See -r and -D.)
- -l - Local. Runs in the current directory only.
- -R - Recursive. Descends into subdirectories (the default). The -R option exists only to counteract a -l in .cvsrc.
- -r REV - Tags revision REV (which may itself be a tag name).

Node: unedit, Next: update, Previous: tag, Up: Commands And Options

### unedit

Synopsis: unedit [OPTIONS] [FILES]

- Alternate names - None
- Requires - Working copy, repository
- Changes - edit/watch lists in the repository

Signals to watchers that you are done editing a file. (See also watch, watchers, edit, and editors.)

Options:

- -l - Local. Signals editing for files in the current working directory only.
- -R - Recursive (opposite of -l). Recursive is the default; the only reason to pass -R is to counteract a -l in your .cvsrc file.

Node: update, Next: watch, Previous: unedit, Up: Commands And Options

### update

Synopsis: update [OPTIONS] [FILES]

- Alternate names - up, upd
- Requires - Working copy, repository
- Changes - Working copy

Merges changes from the repository into your working copy. As a side effect, it indicates which files in your working copy are modified (but if the -Q global option is passed, these indications won't be printed). (See also checkout.)

Options:

- -A - Clears any sticky tags, sticky dates, or sticky RCS keyword expansion modes. This may result in the contents of files changing, if the trunk-head revisions are different from the former sticky revisions. (Think of -A as being like a fresh checkout of the project trunk.)
- -C - Clean out any locally changed files and replace them with the latest versions from the repository. This is not necessarily the same as reverting the files, since the repository may have changed since the last update or checkout. Any local modifications are saved in `.#file.rev`.

  Note: this option was implemented in January 2000; if your CVS was acquired before then, you'd have to upgrade.

- -D DATE - Updates to the most recent revisions no later than DATE. This option is sticky and implies -P. If the working copy has a sticky date, commits are not possible.
- -d - Retrieves absent directories - that is, directories that exist in the repository but not yet in the working copy. Such directories may have been created in the repository after the working copy was checked out. Without this option, update only operates on the directories present in the working copy; new files are brought down from the repository, but new directories are not. (See also -P.)
- -f - Forces to head revision if no matching revision is found with the -D or -r flags.
- -I NAME - Like the -I option of import.
- -j REV[:DATE] or -j REV1[:DATE] -j REV2[:DATE] - Joins, or merges, two lines of development. Ignoring the optional DATE arguments for the moment (we'll get to them later), here's how -j works: If only one -j is given, it takes all changes from the common ancestor to REV and merges them into the working copy. The common ancestor is the latest revision that is ancestral to both the revisions in the working directory and to REV. If two -j options are given, it merges the changes from REV1 to REV2 into the working copy.

  The special tags HEAD and BASE may be used as arguments to -j; they mean the most recent revision in the repository, and the revision on which the current working copy file is based, respectively.

  As for the optional DATE arguments, if REV is a branch, it is normally taken to mean the latest revision on that branch, but you can restrict it to the latest revision no later than DATE. The date should be separated from the revision by a colon, with no spaces, for instance:

                floss$ cvs update -j ABranch:1999-07-01 -j ABranch:1999-08-01

  In this example, different dates on the same branch are used, so the effect is to take the changes on that branch from July to August and merge them into the working copy. However, note that there is no requirement that the branch be the same in both -j options.

- -k MODE - Does RCS keyword substitution according to MODE. (See the section Keyword Substitution (RCS Keywords) later in this chapter.) The mode remains sticky on the working copy, so it will affect future updates (but see -A).
- -l - Local. Updates the current directory only.
- -P - Prunes empty directories. Any CVS-controlled directory that contains no files at the end of the update are removed from the working copy. (See also -d.)
- -p - Sends file contents to standard output instead of to the files. Used mainly for reverting to a previous revision without producing sticky tags in the working copy. For example:

                floss$ cvs update -p -r 1.3 README.txt > README.txt

  Now README.txt in the working copy has the contents of its past Revision 1.3, just as if you had hand-edited it into that state.

- -R - Recursive. Descends into subdirectories to update (the default). The only reason you'd specify it is to counteract a -l in .cvsrc.
- -r REV - Updates (or downdates, or crossdates) to revision REV. When updating a whole working copy, REV is most often a tag (regular or branch). However, when updating an individual file, it is just as likely to be a revision number as a tag.

  This option is sticky. If the files are switched to a nonbranch tag or sticky revision, they cannot be committed until the stickiness is removed. (See -A.) If REV was a branch tag, however, commits are possible. They'll simply commit new revisions on that branch.

- -WSPEC - Specifies wrapper-style filters to use during the update. You can use this option multiple times. (See cvswrappers in Repository Administrative Files in this chapter for details about wrapper specs.) There is no space between -W and its argument.

Node: watch, Next: watchers, Previous: update, Up: Commands And Options

### watch

Synopsis: watch on|off|add|remove [OPTIONS] [FILES]

- Alternate names - None
- Requires - Working copy, repository
- Changes - Watch list in repository

Sets a watch on one or more files. Unlike most CVS commands, watch requires a further subcommand to do something useful. (See also watchers, edit, editors, and unedit, and users.)

Subcommands:

- on - Declares that the files are being watched. This means that they are created read-only on checkout, and users should do cvs edit to make them read-write (and notify any watchers that the file is now being edited). Turning on a watch does not add you to the watch list for any files. (See `watch add` and `watch remove` for that.)
- off - Opposite of watch on. Declares that the files are no longer being watched.
- add - Adds you to the list of watchers for this file. You are notified when someone commits or runs cvs edit or cvs unedit (but see the -a option).
- remove - Opposite of watch add. Removes you from the list of watchers for this file.

Options (for use with any watch subcommand). All three options have the same meanings as for edit:

- -a ACTIONS
- -l
- -R

Node: watchers, Previous: watch, Up: Commands And Options

### watchers

Synopsis: watchers [OPTIONS] [FILES]

- Alternate names - None
- Requires - Working copy, repository
- Changes - Nothing

Shows who's watching what files.

Options - these options mean the same thing here as for edit:

- -l
- -R

Node: Keyword Substitution (RCS Keywords), Next: Repository Administrative Files, Previous: Commands And Options, Up: CVS Reference

### Keyword Substitution (RCS Keywords)

CVS can perform certain textual substitutions in files, allowing you to keep some kinds of information automatically up to date in your files. All of the substitutions are triggered by a certain keyword pattern, surrounded by dollar signs. For example,

         $Revision$

in a file expands to something like

         $Revision: 1.5 $

and CVS continues to keep the revision string up to date as new revisions are committed.

Node: Controlling Keyword Expansion, Next: List Of Keywords, Up: Keyword Substitution (RCS Keywords)

### Controlling Keyword Expansion

By default, CVS performs keyword expansion unless you tell it to stop. You can permanently suppress keyword expansion for a file with the -k option when you add the file to the project, or you can turn it off later by invoking admin with -k. The -k option offers several different modes of keyword control; usually you want mode o or b, for example:

         floss$ cvs add -ko chapter-9.sgml

This command added `chapter-9.sgml` to the project with keyword expansion turned off. It sets the file's default keyword expansion mode to `o`, which means no substitution. (Actually, the "o" stands for "old", meaning to substitute the string with its old value, which is the same as substituting it for itself, resulting in no change. I'm sure this logic made sense to somebody at the time.)

Each file's default keyword mode is stored in the repository. However, each working copy can also have its own local keyword substitution mode - accomplished with the -k options to checkout or update. You can also have a mode in effect for the duration of just one command, with the -k option to diff.

Here are all the possible modes, presented with the -k option prepended (as one would type at a command line). Any of these options can be used as either the default or local keyword substitution mode for a file:

- -kkv - Expands to keyword and value. This is the default keyword expansion mode, so you don't need to set it for new files. You might use it to change a file from another keyword mode, however.
- -kkvl - Like -kkv, but includes the locker's name if the revision is currently locked. (See the -l option to admin for more on this.)
- -kk - Won't expand values in keyword strings, just uses the keyword name. For example, with this option,

                $Revision: 1.5 $

  and

                $Revision$

  would both "expand" (okay, contract) to:

                $Revision$

- -ko - Reuses the keyword string found in the file (hence "o" for "old"), as it was in the working file just before the commit.
- -kb - Like -ko, but also suppresses interplatform line-end conversions. The "b" stands for "binary"; it is the mode you should use for binary files.
- -kv - Substitutes the keyword with its value, for example

                $Revision$

  might become:

                1.5

  Of course, after that's happened once, future substitutions will not take place, so this option should be used with care.

Node: List Of Keywords, Previous: Controlling Keyword Expansion, Up: Keyword Substitution (RCS Keywords)

### List Of Keywords

These are all the dollar-sign-delimited keywords that CVS recognizes. Following is a list of the keyword, a brief description, and an example of its expanded form:

- $Author$ - Author of the change:

                $Author: jrandom $

- $Date$ - The date and time of the change, in UTC (GMT):

                $Date: 1999/08/23 18:21:13 $

- $Header$ - Various pieces of information thought to be useful: full path to the RCS file in the repository, revision, date (in UTC), author, state, and locker. (Lockers are rare; although in the following example, qsmith has a lock.):

                $Header: /usr/local/newrepos/myproj/hello.c,v 1.1 1999/06/01 \
                03:21:13 jrandom Exp qsmith $

- $Id$ - Like $Header$, but without the full path to the RCS file:

                $Id: hello.c,v 1.1 1999/06/01 03:21:13 jrandom Exp qsmith $

- $Log$ - The log message of this revision, along with the revision number, date, and author. Unlike other keywords, the previous expansions are not replaced. Instead, they are pushed down, so that the newest expansion appears at the top of an ever-growing stack of $Log$ messages:

                $Log: hello.c,v $    Revision 1.12  1999/07/19 06:12:43  jrandom
                    say hello in Aramaic

  Any text preceding the $Log$ keyword on the same line will be prepended to the downward expansions too; this is so that if you use it in a comment in a program source file, all of the expansion is commented, too.

- $Locker$ - Name of the person who has a lock on this revision (usually no one):

                $Locker: qsmith $

- $Name$ - Name of the sticky tag:

                $Name: release_1_14 $

- $RCSfile$ - Name of the RCS file in the repository:

                $RCSfile: hello.c,v $

- $Revision$ - Revision number:

                $Revision: 1.1 $

- $Source$ - Full path to the RCS file in the repository:

                $Source: /usr/local/newrepos/myproj/hello.c,v $

- $State$ - State of this revision:

                $State: Exp $

Node: Repository Administrative Files, Next: Run Control Files, Previous: Keyword Substitution (RCS Keywords), Up: CVS Reference

### Repository Administrative Files

The repository's administrative files are stored in the CVSROOT subdirectory of the repository. These files control various aspects of CVS's behavior (in that repository only, of course).

You may also want to refer to the discussion of administrative files in Repository Administration, which includes examples.

Node: Storage And Editing, Next: Shared Syntax, Up: Repository Administrative Files

### Storage And Editing

Generally, the administrative files are kept under revision control just like any other file in the repository (the exceptions are noted). However, unlike other files, checked-out copies of the administrative files are stored in the repository, right next to their corresponding RCS files in the `CVSROOT` subdirectory. It is these checked-out copies which actually govern CVS's behavior.

The normal way to modify the administrative files is to check out a working copy of the CVSROOT module, make your changes, and commit. CVS updates the checked-out copies in the repository automatically. (See checkoutlist.) In an emergency, however, it is also possible to edit the checked-out copies in the repository directly.

Node: Shared Syntax, Next: Shared Variables, Previous: Storage And Editing, Up: Repository Administrative Files

### Shared Syntax

In all of the administrative files, a `#` at the beginning of a line signifies a comment; that line is ignored by CVS. A backslash preceding a newline quotes the newline out of existence.

Some of the files (commitinfo, loginfo, taginfo, and rcsinfo) share more syntactic conventions as well. In these files, on the left of each line is a regular expression (which is matched against a file or directory name), and the rest of the line is a program, possibly with arguments, which is invoked if something is done to a file matching the regular expression. The program is run with its working directory set to the top of the repository.

In these files, there are two special regular expressions that may be used: ALL and DEFAULT. ALL matches any file or directory, whether or not there is some other match for it, and DEFAULT matches only if nothing else matched.

Node: Shared Variables, Next: User Variables, Previous: Shared Syntax, Up: Repository Administrative Files

### Shared Variables

The info files also allow certain variables to be expanded at runtime. To expand a variable, precede it with a dollar sign (and put it in curly braces just to be safe). Here are the variables CVS knows about:

- ${CVSROOT} - The top of the repository.
- ${RCSBIN} - (Obsolete) Don't use this variable. It is only applicable in CVS Version 1.9.18 and older. Specifying it now may result in an error.
- ${CVSEDITOR} ${VISUAL} ${EDITOR} - These all expand to the editor that CVS is using for a log message.
- ${USER} - The user running CVS (on the server side).

Node: User Variables, Next: checkoutlist, Previous: Shared Variables, Up: Repository Administrative Files

### User Variables

Users can also set their own variables when they run any CVS command. (See the -s global option.) These variables can be accessed in the `*info` files by preceding them with an equal sign, as in ${=VAR}.

Node: checkoutlist, Next: commitinfo, Previous: User Variables, Up: Repository Administrative Files

### checkoutlist

This contains a list of files for which checked-out copies should be kept in the repository. Each line gives the file name and an error message for CVS to print if, for some reason, the file cannot be checked out in the repository:

         FILENAME  ERROR_MESSAGE

Because CVS already knows to keep checked-out copies of the existing administrative files, they do not need to be listed in checkoutlist. Specifically, the following files never need entries in checkoutlist: loginfo, rcsinfo, editinfo, verifymsg, commitinfo, taginfo, ignore, checkoutlist, cvswrappers, notify, modules, readers, writers, and config.

Node: commitinfo, Next: config, Previous: checkoutlist, Up: Repository Administrative Files

### commitinfo

Specifies programs to run at commit time, based on what's being committed. Each line consists of a regular expression followed by a command template:

         REGULAR_EXPRESSION PROGRAM [ARGUMENTS]

The PROGRAM is passed additional arguments following any arguments you may have written into the template. These additional arguments are the full path to the repository, followed by the name of each file about to be committed. These files can be examined by PROGRAM; their contents are the same as those of the working copy files about to be committed. If PROGRAM exits with nonzero status, the commit fails; otherwise, it succeeds. (See also Shared Syntax earlier in this chapter.)

Node: config, Next: cvsignore, Previous: commitinfo, Up: Repository Administrative Files

### config

Controls various global (non-project-specific) repository parameters. The syntax of each line is

         ParameterName=yes|no

except for the LockDir parameter, which takes an absolute pathname as argument.

The following parameters are supported:

- RCSBIN (default: `=no`) - (Obsolete) This option is silently accepted for backwards compatibility, but no longer has any effect.
- SystemAuth (default: `=no`) - If `yes`, CVS pserver authentication tries the system user database - usually `/etc/passwd` - if a username is not found in `CVSROOT/passwd`. If `no`, the user must exist in `CVSROOT/passwd` to gain access via the `:pserver:` method.
- PreservePermissions (default: `=no`) - If `yes`, CVS tries to preserve permissions and other special file system information (such as device numbers and symbolic link targets) for files. You probably don't want to do this, as it does not necessarily behave as expected. (See the node Special Files in the Cederqvist manual for details.)
- TopLevelAdmin (default: `=no`) - If `yes`, checkouts create a `CVS/` subdirectory next to each working copy tree (in the parent directory of the working copy). This can be useful if you will be checking out many working copies from the same repository; on the other hand, setting it here affects everyone who uses this repository.
- LockDir (unset by default) - The argument after the equal sign is a path to a directory in which CVS can create lockfiles. If not set, lockfiles are created in the repository, in locations corresponding to each project's RCS files. This means that users of those projects must have file-system-level write access to those repository directories.

Node: cvsignore, Next: cvswrappers, Previous: config, Up: Repository Administrative Files

### cvsignore

Ignores certain files when doing updates, imports, or releases. By default, CVS already ignores some kinds of files. (For a full list, see the -I option to import, earlier in this chapter.) You can add to this list by putting additional file names or wildcard patterns in the cvsignore file. Each line gives a file name or pattern, for example:

         README.msdos
         *.html
         blah?.out

This causes CVS to ignore any file named `README.msdos`, any file ending in `.html`, and any file beginning with `blah` and ending with `.out`. (Technically, you can name multiple files or patterns on each line, separated by whitespace, but it is more readable to keep them to one per line. The whitespace separation rule does, unfortunately, mean that there's no way to specify a space in a file name, except to use wildcards.)

A `!` anywhere in the list cancels all previous entries. (See $CVSIGNORE in the section Environment Variables in this chapter for a fuller discussion of ignore processing.)

Node: cvswrappers, Next: editinfo, Previous: cvsignore, Up: Repository Administrative Files

### cvswrappers

Specifies certain filtering behaviors based on file name. Each line has a file-globbing pattern (that is, a file name or file wildcards), followed by an option indicating the filter type and an argument for the option.

Options:

- -m - Specifies an update method. Possible arguments are MERGE, which means to merge changes into working files automatically, and COPY, which means don't try to automerge but present the user with both versions of the file and let them work it out. MERGE is the default, except for binary files (those whose keyword substitution mode is -kb). (See the Keyword Substitution (RCS Keywords) section in this chapter.) Files marked as binary automatically use the COPY method, so there is no need to make a -m COPY wrapper for them.
- -k - Specifies a keyword substitution mode. All of the usual modes are possible. (See the Keyword Substitution (RCS Keywords) section in this chapter for a complete list.)

Here is an example cvswrappers file:

         *.blob    -m COPY
         *.blink   -k o

This cvswrappers file says to not attempt merges on files ending in `.blob` and suppress keyword substitution for files ending in `.blink`. (See also the file `.cvswrappers` in the Run Control Files section in this chapter.)

Node: editinfo, Next: history file, Previous: cvswrappers, Up: Repository Administrative Files

### editinfo

This file is obsolete. Very.

Node: history file, Next: loginfo, Previous: editinfo, Up: Repository Administrative Files

### history file

Stores an ever-accumulating history of activity in the repository, for use by the cvs history command. To disable this feature, simply remove the history file. If you don't remove the file, you should probably make it world-writeable to avoid permission problems later.

The contents of this file do not modify CVS's behavior in any way (except for the output of cvs history, of course).

Node: loginfo, Next: modules, Previous: history file, Up: Repository Administrative Files

### loginfo

Specifies programs to run on the log message for each commit, based on what's being committed. Each line consists of a regular expression followed by a command template:

         REGULAR_EXPRESSION PROGRAM [ARGUMENTS]

The PROGRAM is passed the log message on its standard input.

Several special codes are available for use in the arguments: `%s` expands to the names of the files being committed, `%V` expands to the old revisions from before the commit, and `%v` expands to the new revisions after the commit. When there are multiple files involved, each element of the expansion is separated from the others by whitespace. For example, in a commit involving two files, `%s` might expand into `hello.c README.txt`, and `%v` into `1.17 1.12`.

You may combine codes inside curly braces, in which case, each unit of expansion is internally separated by commas and externally separated from the other units by whitespace. Continuing the previous example, `%{sv}` expands into `hello.c,1.17 README.txt,1.12`.

If any `%` expansion is done at all, the expansion is prefixed by the path to the project subdirectory (relative to the top of the repository). So that last expansion would actually be:

         myproj  hello.c,1.17  README.txt,1.12

If PROGRAM exits with nonzero status, the commit fails; otherwise, it succeeds. (See also the Shared Syntax section in this chapter.)

Node: modules, Next: notify, Previous: loginfo, Up: Repository Administrative Files

### modules

This maps names to repository directories. The general syntax of each line is:

         MODULE [OPTIONS] [&OTHERMODULE...] [DIR] [FILES]

DIR need not be a top-level project directory - it could be a subdirectory. If any FILES are specified, the module consists of only those files from the directory.

An ampersand followed by a module name means to include the expansion of that module's line in place.

Options:

- -a - This is an alias module, meaning it expands literally to everything after the OPTIONS. In this case, the usual DIR/FILES behavior is turned off, and everything after the OPTIONS is treated as other modules or repository directories.

  If you use the -a option, you may exclude certain directories from other modules by putting them after an exclamation point (!). For example

                top_proj -a !myproj/a-subdir !myproj/b-subdir myproj

  means that checking out `top_proj` will get all of `myproj` except `a-subdir` and `b-subdir`.

- -d NAME - Names the working directory NAME instead of the module name.
- -e PROGRAM - Runs PROGRAM whenever files in this module are exported.
- -i PROGRAM - Runs PROGRAM whenever files in this module are committed. The program is given a single argument - the full pathname in the repository of the file in question. (See commitinfo, loginfo, and verifymsg for more sophisticated ways to run commit-triggered programs.)
- -o PROGRAM - Runs PROGRAM whenever files in this module are checked out. The program is given a single argument, the name of the module.
- -s STATUS - Declares a status for the module. When the modules file is printed (with cvs checkout -s), the modules are sorted by module status and then by name. This option has no other effects in CVS, so go wild. You can use it to sort anything - status, person responsible for the module, or the module's file language, for example.
- -t PROGRAM - Runs PROGRAM whenever files in this module are tagged with cvs rtag. The program is passed two arguments: the name of the module and the tag name. The program is not used for tag, only for rtag. I have no idea why this distinction is made. You may find the taginfo file more useful if you want to run programs at tag time.
- -u PROGRAM - Runs PROGRAM whenever a working copy of the module is updated from its top-level directory. The program is given a single argument, the full path to the module's repository.

Node: notify, Next: passwd, Previous: modules, Up: Repository Administrative Files

### notify

Controls how the notifications for watched files are performed. (You may want to read up on the watch and edit commands, or see the section Watches (CVS As Telephone) in Advanced CVS.) Each line is of the usual form:

REGULAR_EXPRESSION PROGRAM [ARGUMENTS]

A `%s` in ARGUMENTS is expanded to the name of the user to be notified, and the rest of the information regarding the notification is passed to PROGRAM on standard input (usually this information is a brief message suitable for emailing to the user). (See the section Shared Syntax earlier in this chapter.)

As shipped with CVS, the notify file has one line

         ALL mail %s -s "CVS notification"

which is often all you need.

Node: passwd, Next: rcsinfo, Previous: notify, Up: Repository Administrative Files

### passwd

Provides authentication information for the pserver access method. Each line is of the form:

USER:ENCRYPTED_PASSWORD[:SYSTEM_USER]

If no SYSTEM_USER is given, USER is taken as the system username.

Node: rcsinfo, Next: taginfo, Previous: passwd, Up: Repository Administrative Files

### rcsinfo

Specifies a form that should be filled out for log messages that are written with an interactive editor. Each line of rcsinfo looks like:

REGULAR_EXPRESSION FILE_CONTAINING_TEMPLATE

This template is brought to remote working copies at checkout time, so if the template file or rcsinfo file changes after checkout, the remote copies won't know about it and will continue to use the old template. (See also the section Shared Syntax in this chapter.)

Node: taginfo, Next: users, Previous: rcsinfo, Up: Repository Administrative Files

### taginfo

Runs a program at tag time (usually done to check that the tag name matches some pattern). Each line is of the form:

REGULAR_EXPRESSION PROGRAM

The program is handed a set group of arguments. In order, they are the tag name, the operation (see below), the repository, and then as many file name/revision-number pairs as there are files involved in the tag. The file/revision pairs are separated by whitespace, like the rest of the arguments.

The operation is one of `add`, `mov`, or `del` (`mov` means the -F option to tag was used).

If PROGRAM exits with nonzero status, the tag operation will not succeed. (See also the section Shared Syntax in this chapter.)

Node: users, Next: val-tags, Previous: taginfo, Up: Repository Administrative Files

### users

Maps usernames to email addresses. Each line looks like:

USERNAME:EMAIL_ADDRESS

This sends watch notifications to EMAIL_ADDRESS instead of to USERNAME at the repository machine. (All this really does is control the expansion of %s in the notify file.) If EMAIL_ADDRESS includes whitespace, make sure to surround it with quotes.

If user aliasing is being used in the passwd file, the username that will be matched is the CVS username (the one on the left), not the system username (the one on the right, if any).

Node: val-tags, Next: verifymsg, Previous: users, Up: Repository Administrative Files

### val-tags

Caches valid tag names for speedier lookups. You should never need to edit this file, but you may need to change its permissions, or even ownership, if people are having trouble retrieving or creating tags.

Node: verifymsg, Previous: val-tags, Up: Repository Administrative Files

### verifymsg

Used in conjunction with rcsinfo to verify the format of log messages. Each line is of the form:

REGULAR_EXPRESSION PROGRAM [ARGUMENTS]

The full path to the current log message template (see rcsinfo earlier in this chapter) is appended after the last argument written in the verifymsg file. If PROGRAM exits with nonzero status, the commit fails.

Node: Run Control Files, Next: Working Copy Files, Previous: Repository Administrative Files, Up: CVS Reference

### Run Control Files

There are a few files on the client (working copy) side that affect CVS's behavior. In some cases, they are analogs of repository administrative files; in other cases, they control behaviors that are only appropriate for the client side.

### `.cvsrc`

Specifies options that you want to be used automatically with every CVS command. The format of each line is

COMMAND OPTIONS

where each COMMAND is an unabbreviated CVS command, such as checkout or update (but not co or up). The OPTIONS are those that you want to always be in effect when you run that command. Here is a common `.cvsrc` line:

         update -d -P

To specify global options, simple use cvs as the COMMAND.

### `.cvsignore`

Specifies additional ignore patterns. (See cvsignore in the Repository Administrative Files section in this chapter for the syntax.)

You can have a .cvsignore file in your home directory, which will apply every time you use CVS. You can also have directory-specific ones in each project directory of a working copy (these last only apply to the directory where the .cvsignore is located, and not to its subdirectories).

(See $CVSIGNORE in the section Environment Variables in this chapter, for a fuller discussion of ignore processing.)

### `.cvspass`

Stores passwords for each repository accessed via the pserver method. Each line is of the form:

REPOSITORY LIGHTLY_SCRAMBLED_PASSWORD

The password is essentially stored in cleartext - a very mild scrambling is done to prevent accidental compromises (such as the root user unintentionally looking inside the file). However, this scrambling will not deter any serious-minded person from gaining the password if they get access to the file.

The .cvspass file is portable. You can copy it from one machine to another and have all of your passwords at the new machine, without ever having run cvs login there. (See also the login and logout commands.)

### `.cvswrappers`

This is a client side version of the cvswrappers file. (See the Repository Administrative Files section in this chapter.) There can be a `.cvswrappers` file in your home directory and in each directory of a working copy directory, just as with `.cvsignore`.

Node: Working Copy Files, Next: Environment Variables, Previous: Run Control Files, Up: CVS Reference

### Working Copy Files

The CVS/ administrative subdirectories in each working copy contain some subset of the following files.

- CVS/Base/
- CVS/Baserev
- CVS/Baserev.tmp
- CVS/Checkin.prog
- CVS/Entries
- CVS/Entries.Backup
- CVS/Entries.Log
- CVS/Entries.Static
- CVS/Notify
- CVS/Notify.tmp
- CVS/Repository
- CVS/Root
- CVS/Tag
- CVS/Template
- CVS/Update.prog

Here is what each file or directory does:

### `CVS/Base/` (directory)

If watches are on, `cvs edit` stores the original copy of the file in this directory. That way, `cvs unedit` can work even if it can't reach the server.

### `CVS/Baserev`

Lists the revision for each file in `Base/`. Each line looks like this:

         FILE/REVISION/EXPANSION

EXPANSION is currently ignored to allow for, well, future expansion.

### `CVS/Baserev.tmp`

This is the temp file for the preceding. (See `CVS/Notify.tmp` or `CVS/Entries.Backup` later on for further explanation.)

### `CVS/Checkin.prog`

Records the name of the program specified by the -i option in the modules file. (See the Repository Administrative Files section in this chapter.)

### `CVS/Entries`

Stores the revisions for the files in this directory. Each line is of the form:

         [CODE_LETTER]/FILE/REVISION/DATE/[KEYWORD_MODE]/[STICKY_OPTION]

If CODE_LETTER is present, it must be `D` for directory (anything else is silently ignored by CVS, to allow for future expansion), and the rest of the items on the line are absent.

This file is always present.

### `CVS/Entries.Backup`

This is just a temp file. If you're writing some program to modify the `Entries` file, have it write the new contents to `Entries.backup` and then atomically rename it to `Entries`.

### `CVS/Entries.Log`

This is basically a patch file to be applied to `Entries` after `Entries` has been read (this is an efficiency hack, to avoid having to rewrite all of `Entries` for every little change). The format is the same as `Entries`, except that there is an additional mandatory code letter at the front of every line: An `A` means this line is to be added to what's in `Entries`; `R` means it's to be removed from what's in `Entries`. Any other letters should be silently ignored, to allow for future expansion.

### `CVS/Entries.Static`

If this file exists, it means only part of the directory was fetched from the repository, and CVS will not create additional files in that directory. This condition can usually be cleared by using `update -d`.

### `CVS/Notify`

Stores notifications that have not yet been sent to the server.

### `CVS/Notify.tmp`

Temp file for `Notify`. The usual procedure for modifying `Notify` is to write out `Notify.tmp` and then rename it to `Notify`.

### `CVS/Repository`

The path to the project-specific subdirectory in the repository. This may be an absolute path, or it may be relative to the path given in Root.

This file is always present.

### `CVS/Root`

This is the repository; that is, the value of the `$CVSROOT` environment variable or the argument to the -d global option.

This file is always present.

### `CVS/Tag`

If there is a sticky tag or date on this directory, it is recorded in the first line of the file. The first character is a single letter indicating the type of tag: `T`, `N`, or `D`, for branch tag, nonbranch tag, or date respectively. The rest of the line is the tag or date itself.

### `CVS/Template`

Contains a log message template as specified by the rcsinfo file. (See Repository Administrative Files earlier in this chapter.) It is relevant only for remote working copies; working copies on the same machine as the repository just read rcsinfo directly.

### `CVS/Update.prog`

Records the name of the program specified by the -u option in the modules file. (See the Repository Administrative Files section in this chapter.)

Node: Environment Variables, Previous: Working Copy Files, Up: CVS Reference

### Environment Variables

These are all the environment variables that affect CVS.

Node: $COMSPEC, Next: $CVS_CLIENT_LOG, Up: Environment Variables

### $COMSPEC

This is used in OS/2 only; it specifies the name of the command interpreter. It defaults to `CMD.EXE`.

Node: $CVS_CLIENT_LOG, Next: $CVS_CLIENT_PORT, Previous: $COMSPEC, Up: Environment Variables

### $CVS_CLIENT_LOG

Used for debugging the client/server protocol. Set this variable to a file name before you start using CVS; all traffic to the server will be logged in filename.in, and everything from the server will be logged in filename.out.

Node: $CVS_CLIENT_PORT, Next: $CVSEDITOR, Previous: $CVS_CLIENT_LOG, Up: Environment Variables

### $CVS_CLIENT_PORT

Used in Kerberos-authenticated client/server access.

Node: $CVSEDITOR, Next: $CVSIGNORE, Previous: $CVS_CLIENT_PORT, Up: Environment Variables

### $CVSEDITOR

Specifies the program to use to edit log messages for commits. This overrides `$EDITOR` and `$VISUAL`.

Node: $CVSIGNORE, Next: $CVS_IGNORE_REMOTE_ROOT, Previous: $CVSEDITOR, Up: Environment Variables

### $CVSIGNORE

A whitespace-separated list of file names and wildcard patterns that CVS should ignore. (See also the -I option to the import command.)

This variable is appended last to the ignore list during a command. The list is built up in this order: `CVSROOT/cvsignore`, the `.cvsignore` file in your home directory, the `$CVSIGNORE` variable, any -I command option, and finally the contents of `.cvsignore` files in the working copy used as CVS works in each directory. A `!` as the ignore specification at any point nullifies the entire ignore list built up to that point.

Node: $CVS_IGNORE_REMOTE_ROOT, Next: $CVS_PASSFILE, Previous: $CVSIGNORE, Up: Environment Variables

### $CVS_IGNORE_REMOTE_ROOT

Recently obsolete.

Node: $CVS_PASSFILE, Next: $CVS_RCMD_PORT, Previous: $CVS_IGNORE_REMOTE_ROOT, Up: Environment Variables

### $CVS_PASSFILE

Tells CVS to use some file other than .cvspass in your home directory. (See the file `.cvspass` in the Run Control Files section in this chapter.)

Node: $CVS_RCMD_PORT, Next: $CVSREAD, Previous: $CVS_PASSFILE, Up: Environment Variables

### $CVS_RCMD_PORT

Specifies the port number to contact the rcmd daemon on the server side. (This variable is currently ignored in Unix CVS clients.)

Node: $CVSREAD, Next: $CVSROOT, Previous: $CVS_RCMD_PORT, Up: Environment Variables

### $CVSREAD

Makes working copy files read-only on checkout and update, if possible (the default is for them to be read-write). (See also the -r global option.)

Node: $CVSROOT, Next: $CVS_RSH, Previous: $CVSREAD, Up: Environment Variables

### $CVSROOT

This specifies the path to the repository. This is overridden with the -d global option and by the ambient repository for a given working copy. The path to the repository may be preceded by an access method, username, and host, according to the following syntax:

         [[:METHOD:][[USER@]HOST]:]/REPOSITORY_PATH

See the -d global option, in the section Global Options near the beginning of this chapter, for a list of valid methods.

Node: $CVS_RSH, Next: $CVS_SERVER, Previous: $CVSROOT, Up: Environment Variables

### $CVS_RSH

Specifies an external program for connecting to the server when using the `:ext:` access method. Defaults to `rsh`, but `ssh` is a common replacement value.

Node: $CVS_SERVER, Next: $CVS_SERVER_SLEEP, Previous: $CVS_RSH, Up: Environment Variables

### $CVS_SERVER

Program to invoke for CVS on the server side. Defaults to `cvs`, of course.

Node: $CVS_SERVER_SLEEP, Next: $CVSUMASK, Previous: $CVS_SERVER, Up: Environment Variables

### $CVS_SERVER_SLEEP

Delays the start of the server child process by the specified number of seconds. This is used only for debugging, to allow time for a debugger to connect.

Node: $CVSUMASK, Next: $CVSWRAPPERS, Previous: $CVS_SERVER_SLEEP, Up: Environment Variables

### $CVSUMASK

Permissions for files and directories in the repository. (You probably don't want to set this; it doesn't work for client/server anyway.)

Node: $CVSWRAPPERS, Next: $EDITOR, Previous: $CVSUMASK, Up: Environment Variables

### $CVSWRAPPERS

A whitespace-separated list of file names, wildcards, and arguments that CVS should use as wrappers. (See cvswrappers in the Repository Administrative Files section in this chapter for more information.)

Node: $EDITOR, Next: $HOME %HOMEDRIVE% %HOMEPATH%, Previous: $CVSWRAPPERS, Up: Environment Variables

### $EDITOR

(See $CVSEDITOR.)

Node: $HOME %HOMEDRIVE% %HOMEPATH%, Next: $PATH, Previous: $EDITOR, Up: Environment Variables

### $HOME %HOMEDRIVE% %HOMEPATH%

Where the `.cvsrc`, `.cvspass`, and other such files are found (under Unix, only `$HOME` is used). In Windows NT, `%HOMEDRIVE%` and `%HOMEPATH%` might be set for you; in Windows 95, you may need to set them for yourself.

In Windows 95, you may also need to set `%HOME%`. Make sure not to give it a trailing backslash; use set `HOME=C:` or something similar.

Node: $PATH, Next: $TEMP $TMP $TMPDIR, Previous: $HOME %HOMEDRIVE% %HOMEPATH%, Up: Environment Variables

### $PATH

Obsolete.

Node: $TEMP $TMP $TMPDIR, Next: $VISUAL, Previous: $PATH, Up: Environment Variables

### $TEMP $TMP $TMPDIR

Where temporary files go (the server uses TMPDIR; Windows NT uses TMP). Setting this on the client side will not affect the server. Setting this on either side will not affect where CVS stores temporary lock files. (See config in the Repository Administrative Files section in this chapter for more information.)

Node: $VISUAL, Previous: $TEMP $TMP $TMPDIR, Up: Environment Variables

### $VISUAL

(See $CVSEDITOR.)

Node: Third-Party Tools, Next: Index, Previous: CVS Reference, Up: Top

## Third-Party Tools

Many people have written programs to augment CVS. I call these third-party tools because they have their own maintainers, separate from the CVS development team. Most of these programs are not distributed with CVS, although some are. This chapter covers third-party tools that I have found useful, but that are not distributed with CVS.

Although there are some very popular and widely used non-command-line or non-Unix interfaces to CVS (download sites are listed in Repository Administration), this chapter does not discuss most of them. Their popularity makes it easy to find out more about them from mailing lists and newsgroups. One exception to this is the Emacs pcl-cvs interface, which is very useful, but sometimes tricky to install.

Node: pcl-cvs -- An Emacs Interface To CVS, Next: cvsutils -- General Utilities For Use With CVS, Up: Third-Party Tools

### pcl-cvs - An Emacs Interface To CVS

Depends on: Emacs, Elib

URLs:

- ftp://rum.cs.yale.edu/pub/monnier/pcl-cvs/
- ftp://ftp.lysator.liu.se/pub/emacs/pcl-cvs-1.05.tar.gz
- ftp://ftp.red-bean.com/pub/kfogel/pcl-cvs-1.05.tar.gz

Authors: Per Cederqvist and Stefan Monnier (current maintainer)

`pcl-cvs` is one of two Emacs/CVS interfaces. The other is the native VC (Version Control) interface built into Emacs. I prefer pcl-cvs because it was written exclusively for CVS and, therefore, works smoothly with the CVS way of doing things. VC, on the other hand, was designed to work with several different back-end version control systems - RCS and SCCS, as well as CVS - and is not really "tuned" for CVS. For example, VC presents a file-based rather than a directory-based interface to revision control.

The advantages of pcl-cvs are strong enough that many people choose to download and install it rather than use VC. Unfortunately, pcl-cvs has two disadvantages: It can be a bit tricky to install (much of this section is devoted to overcoming possible installation hurdles), and its recent releases are a bit unstable.

The latter problem is likely to be temporary, but it does raise the question of which version to use. Stefan Monnier has just recently taken over the pcl-cvs maintainership; the latest release, 2.9.6 (available from the first URL in the preceding list), was a bit bumpy when I tried it. No doubt the problems will be smoothed out soon, but in the meantime, you might want to use an older version. Because I've been using Version 1.05 daily for a long time now and it's performed quite well, I'm going to document that version here. Fortunately, the installation procedures don't change much from version to version. If you decide to use pcl-cvs, I suggest that you check Monnier's download site for a version newer than 2.9.6; if there is one, try it out before regressing all the way to 1.05.

You'll notice that two URLs are given for Version 1.05. The first is Per Cederqvist's site, where he still makes available an old archive of pcl-cvs. However, since I'm not sure how much longer his archive will stay around, I'm also making the 1.05 distribution available from ftp.red-bean.com.

Although the rest of these instructions use examples from a Version 1.05 distribution, they should apply to later versions as well.

Node: Installing pcl-cvs, Next: Using pcl-cvs, Up: pcl-cvs -- An Emacs Interface To CVS

### Installing pcl-cvs

If you don't normally deal with Emacs installation and site-maintenance issues, the pcl-cvs installation procedure may seem a bit daunting. A little background on how Emacs works may help.

Most higher-level Emacs features are written in a language called "Emacs Lisp" (Emacs itself is essentially an interpreter for this language). People add new features to Emacs by distributing files of Emacs Lisp code. `pcl-cvs` is written in this language, and it depends on a library of useful, generic Emacs Lisp functions called Elib (also written in part by Per Cederqvist, but distributed separately from pcl-cvs).

Elib is not included in the regular Emacs distribution (at least not FSF Emacs; I don't know about XEmacs), so you may have to download and install it yourself before you can use pcl-cvs. You can get it from ftp://ftp.lysator.liu.se/pub/emacs/elib-1.0.tar.gz. Installation instructions are contained within the package.

Once Elib is installed, you're ready to build and install pcl-cvs. These instructions applies both to Version 1.05 and the 2.x series (although you should check the NEWS and INSTALL files in newer distributions to see what's changed).

First, unpack pcl-cvs (I'm using Version 1.05, but it could just as easily have been 2.9.6)

         floss$ zcat pcl-cvs-1.05.tar.gz | tar xvf -
         pcl-cvs-1.05/
         pcl-cvs-1.05/README
         pcl-cvs-1.05/NEWS
         pcl-cvs-1.05/INSTALL
         pcl-cvs-1.05/ChangeLog
         pcl-cvs-1.05/pcl-cvs.el
         pcl-cvs-1.05/pcl-cvs.texinfo
         pcl-cvs-1.05/compile-all.el
         pcl-cvs-1.05/pcl-cvs-lucid.el
         pcl-cvs-1.05/pcl-cvs-startup.el
         pcl-cvs-1.05/pcl-cvs.info
         pcl-cvs-1.05/Makefile
         pcl-cvs-1.05/texinfo.tex

and go into the source tree's top level:

         floss$ cd pcl-cvs-1.05/

A Makefile is supplied there. According to the instructions in the INSTALL file, you're supposed to edit a few paths at the top of the Makefile and then run:

         floss$ make install

If that works, great. However, this sometimes results in an error (the pcl-cvs code itself is very portable, but its installation procedures sometimes are not). Do this if you get an error:

         floss$ make clean
         floss$ make

If all goes well, these commands accomplish a significant part of the installation by byte-compiling all of the Emacs Lisp files. (Byte-compiling converts a file of human-readable Emacs Lisp code - an .el file - into a more compact and efficient representation - an .elc file. Emacs can load and run an .elc file with better performance than it can a plain .el file.)

I'll proceed as though the byte-compilation stage has succeeded. If the byte compilation does not appear to succeed, don't worry: The .elc files are a luxury, not a necessity. They improve performance slightly, but you can run pcl-cvs from the raw .el files with no problem.

If the make install failed, the next step is to get the Emacs Lisp (whether .el or .elc) into a directory where Emacs can load it automatically. Emacs has a designated directory on the system for locally installed Lisp. To find this directory - it will have a file named `default.el` in it - check the following locations, in this order:

1. /usr/share/emacs/site-lisp/
2. /usr/local/share/emacs/site-lisp/
3. /usr/lib/emacs/site-lisp/
4. /usr/local/lib/emacs/site-lisp/

Once you've found your site-lisp directory, copy all of the Lisp files to it (you may have to be root to do this):

         floss# cp -f *.el *.elc /usr/share/emacs/site-lisp/

The last step is to tell Emacs about the entry points to pcl-cvs (the main one being the function cvs-update), so it will know to load the pcl-cvs code on demand. Because Emacs always reads the default.el file when it starts up, that's where you need to list the pcl-cvs entry points.

Fortunately, pcl-cvs provides the necessary content for default.el. Simply put the contents of pcl-cvs-startup.el into default.el (or perhaps into your .emacs, if you're just installing this for yourself) and restart your Emacs.

You may also want to copy the .info files into your info tree and add pcl-cvs to the table of contents in the dir file.

Node: Using pcl-cvs, Next: Error Handling In pcl-cvs, Previous: Installing pcl-cvs, Up: pcl-cvs -- An Emacs Interface To CVS

### Using pcl-cvs

Once installed, pcl-cvs is very easy to use. You just run the function cvs-update, and pcl-cvs brings up a buffer showing what files in your working copy have been modified or updated. From there, you can commit, do diffs, and so on.

Because cvs-update is the main entry point, I suggest that you bind it to a convenient key sequence before going any further. I have it bound to `Ctrl+c v` in my .emacs:

         (global-set-key "\C-cv" 'cvs-update)

Otherwise, you can run it by typing `M-x cvs-update` (also known as `Esc-x cvs-update`).

When invoked, cvs-update runs cvs update as if in the directory of the file in the current buffer - just as if you typed cvs update on the command line in that directory. Here's an example of what you might see inside Emacs:

         PCL-CVS release 1.05 from CVS release $Name:  $.
         Copyright (C) 1992, 1993 Per Cederqvist
         Pcl-cvs comes with absolutely no warranty; for details consult the manual.
         This is free software, and you are welcome to redistribute it under certain
         conditions; again, consult the TeXinfo manual for details.
          Modified ci README.txt
          Modified ci fish.c
         ---------- End ----

Two files have been locally modified (some versions of pcl-cvs show the subdirectories where the files are located). The next logical action is to commit one or both of the files, which is what the ci on each line means. To commit one of them, go to its line and type `c`. You are brought to a log message buffer, where you can type a log message as long as you want (real log message editing is the major advantage of pcl-cvs over the command line). Type `Ctrl+c Ctrl+c` when done to complete the commit.

If you want to commit multiple files at once, sharing a log message, first use m to mark the files that you intend to commit. An asterisk appears next to each file as you mark it:

         PCL-CVS release 1.05 from CVS release $Name:  $.
         Copyright (C) 1992, 1993 Per Cederqvist
         Pcl-cvs comes with absolutely no warranty; for details consult the manual.
         This is free software, and you are welcome to redistribute it under certain
         conditions; again, consult the TeXinfo manual for details.
         * Modified ci README.txt
         * Modified ci fish.c
         ---------- End ----

Now when you type c anywhere, it applies to all (and only) the marked files. Write the log message and commit them with `Ctrl+c Ctrl+c` as before.

You can also type `d` to run cvs diff on a file (or on marked files) and `f` to bring a file into Emacs for editing. Other commands are available; type `Ctrl+h` m in the update buffer to see what else you can do.

Node: Error Handling In pcl-cvs, Next: The Future Of pcl-cvs, Previous: Using pcl-cvs, Up: pcl-cvs -- An Emacs Interface To CVS

### Error Handling In pcl-cvs

The pcl-cvs program has historically had an odd way of dealing with error and informational messages from CVS (although this may be corrected in the latest versions). When it encounters a message from CVS that it doesn't know about, it gets hysterical and throws you into a mail buffer, ready to send a pregenerated bug report to the author of pcl-cvs. Unfortunately, among the CVS messages that pcl-cvs may not know about are the ones associated with conflicting merges, which, although not common, certainly do occur from time to time.

If pcl-cvs suddenly dumps you into a mail buffer, don't panic. Read over the contents of the buffer carefully - the offending CVS output should be in there somewhere. If it looks like a merge, you can just get rid of the mail buffer and rerun cvs-update. It should now succeed, because CVS won't output any merge messages (because the merge has already taken place).

(Update: this problem appears to have been fixed in more recent versions of pcl-cvs, so very probably you can ignore this entire warning.)

Node: The Future Of pcl-cvs, Previous: Error Handling In pcl-cvs, Up: pcl-cvs -- An Emacs Interface To CVS

### The Future Of pcl-cvs

Although I may be giving you the impression that pcl-cvs is barely maintained and a risky investment, the instability appears to be temporary. Stefan Monnier is a responsive maintainer (I contacted him several times during the writing of this chapter, and he always answered right away; he is already making headway on some of the bugs in Version 2.9.6). Very likely by the time this is published, you will be able to download Version 2.9.7 or later with confidence.

In fact, I just now got an encouraging email on this topic from Greg Woods, a former maintainer of pcl-cvs, reprinted here with his permission:

         From: woods@most.weird.com (Greg A. Woods)
         Subject: Re: pcl-cvs maintenance status, stability of recent "release"s?
         To: kfogel@red-bean.com
         Date: Sun, 29 Aug 1999 18:59:19 -0400 (EDT)

         [...]
         I've been using Stefan's releases for some time now, and indeed I have
         abandoned my own branch of it.

         He's done a lot of really good work on PCL-CVS and except for a few odd
         quirks in the 2.9.6 version I'm using daily now it is quite usable (and
         is approximately infinitely more usable with modern CVS than the one
         that was in the CVS distribution! ;-).

         I've added a pcl-cvs.README file to my FTP site to point out that the
         files there are indeed quite old (at least in Internet time! ;-) and to
         give a pointer to Stefan's FTP site too.

         [...]

In a later email, Greg said that the FSF is considering including pcl-cvs in their next release of Emacs (20.5), which would render most of the preceding installation advice obsolete. Sigh. It's hard to keep up with free software, sometimes.

Node: cvsutils -- General Utilities For Use With CVS, Next: cvs2cl -- Generate GNU-Style ChangeLogs, Previous: pcl-cvs -- An Emacs Interface To CVS, Up: Third-Party Tools

### cvsutils - General Utilities For Use With CVS

Depends on: Perl

URLs:

- http://www.red-bean.com/cvsutils

Authors: Tom Tromey (original author) and Pavel Roskin (current maintainer)

The suite of small programs called `cvsutils` generally (although not always) performs offline operations in the CVS working copy. Offline operations are those that can be done without contacting the repository, while still leaving the working copy in a consistent state for the next time the repository is contacted. Offline behavior can be extremely handy when your network connection to the repository is slow or unreliable.

The cvsutils programs are listed below in approximate order of usefulness (according to my opinion), with the more useful ones coming first. Coincidentally, this also arranges them by safety. Safety is an issue because some of these utilities can, in their normal course of operation, cause you to lose local modifications or files from your working copy. Therefore, read the descriptions carefully before using these utilities.

This documentation is accurate as of Version 0.1.4. Be sure to read the README file in any later versions for more up-to-date information.

Node: cvsu, Next: cvsdo, Up: cvsutils -- General Utilities For Use With CVS

### cvsu

Danger level: None

Contacts repository: No

This does an offline cvs update by comparing the timestamps of files on disk with their timestamps recorded in CVS/Entries. You can thus tell which files have been locally modified and which files are not known to be under CVS control. Unlike `cvs update`, cvsu does not bring down changes from the repository.

Although it can take various options, cvsu is most commonly invoked without any options:

         floss$ cvsu
         ? ./bar
         ? ./chapter-10.html
         M ./chapter-10.sgml
         D ./out
         ? ./safe.sh
         D ./tools

The left-side codes are like the output of cvs update, except that `D` means directory. This example shows that chapter-10.sgml has been modified locally. What the example doesn't show is that cvsu ran instantly, whereas a normal cvs update would have required half a minute or so over my slow modem line. Run

         floss$ cvsu --help

to see a list of options.

Node: cvsdo, Next: cvschroot, Previous: cvsu, Up: cvsutils -- General Utilities For Use With CVS

### cvsdo

Danger level: Low to none

Contacts repository: No

This can simulate the working copy effects of cvs add and cvs remove, but without contacting the repository. Of course, you'd still have to commit the changes to make them take effect in the repository, but at least the add and remove commands themselves can be sped up this way. Here's how to use it

         floss$ cvsdo add FILENAME

or

         floss$ cvsdo remove FILENAME

To see a list of further options, run:

         floss$ cvsdo --help

Node: cvschroot, Next: cvsrmadm, Previous: cvsdo, Up: cvsutils -- General Utilities For Use With CVS

### cvschroot

Danger level: Low

Contacts repository: No

This deals with a repository move by tweaking the working copy to point to the new repository. This is useful when a repository is copied en masse to a new location. When that happens, none of the revisions are affected, but the CVS/Root (and possibly the CVS/Repository) file of every working copy must be updated to point to the new location. Using cvschroot is a lot faster than checking out a new copy. Another advantage is that it doesn't lose your local changes.

Usage:

         floss$ cvschroot NEW_REPOS

For example:

         floss$ cvschroot :pserver:newuser@newhost.wherever.com:/home/cvs/myproj

Node: cvsrmadm, Next: cvspurge, Previous: cvschroot, Up: cvsutils -- General Utilities For Use With CVS

### cvsrmadm

Danger level: Low to medium

Contacts repository: No

This removes all of the CVS/ administrative subdirectories in your working copy, leaving behind a tree similar to that created by cvs export.

Although you won't lose any local changes by using cvsrmadm, your working copy will no longer be a working copy.

Use with caution.

Node: cvspurge, Next: cvsdiscard, Previous: cvsrmadm, Up: cvsutils -- General Utilities For Use With CVS

### cvspurge

Danger level: Medium

Contacts repository: No

This removes all non-CVS-controlled files in your working copy. It does not undo any local changes to CVS-controlled files.

Use with caution.

Node: cvsdiscard, Next: cvsco, Previous: cvspurge, Up: cvsutils -- General Utilities For Use With CVS

### cvsdiscard

Danger level: Medium to high

Contacts repository: Maybe

This is the complement of cvspurge. Instead of removing unknown files but keeping your local changes, cvsdiscard undoes any local changes (replacing those files with fresh copies from the repository), but keeps unknown files.

Use with extreme caution.

Node: cvsco, Next: cvsdate, Previous: cvsdiscard, Up: cvsutils -- General Utilities For Use With CVS

### cvsco

Danger level: High

Contacts repository: Maybe

This is the union of cvspurge and cvsdiscard. It undoes any local changes and removes unknown files from the working copy.

Use with truly paranoid caution.

Node: cvsdate, Previous: cvsco, Up: cvsutils -- General Utilities For Use With CVS

### cvsdate

This script is apparently incomplete and possibly may never be finished. (See the README file for details.)

Node: cvs2cl -- Generate GNU-Style ChangeLogs, Next: cvslock -- Lock Repositories For Atomicity, Previous: cvsutils -- General Utilities For Use With CVS, Up: Third-Party Tools

### cvs2cl - Generate GNU-Style ChangeLogs

Depends on: Perl

URL: http://www.red-bean.com/~kfogel/cvs2cl.shtml

cvs2cl.pl condenses and reformats the output of cvs log to create a GNU-style ChangeLog file for your project. ChangeLogs are chronologically organized documents showing the change history of a project, with a format designed specifically for human-readability (see the following examples).

The problem with the `cvs log` command is that it presents its output on a per-file basis, with no acknowledgement that the same log message, appearing at roughly the same time in different files, implies that those revisions were all part of a single commit. Thus, reading over log output to get an overview of project development is a hopeless task - you can really only see the history of one file at a time.

In the ChangeLog produced by cvs2cl.pl, identical log messages are unified, so that a single commit involving a group of files shows up as one entry. For example:

         floss$ cvs2cl.pl -r
         cvs log: Logging .
         cvs log: Logging a-subdir
         cvs log: Logging a-subdir/subsubdir
         cvs log: Logging b-subdir
         floss$ cat ChangeLog
         ...
         1999-08-29 05:44  jrandom

            * README (1.6), hello.c (2.1), a-subdir/whatever.c (2.1),
            a-subdir/subsubdir/fish.c (2.1): Committing from pcl-cvs 2.9, just
            for kicks.

         1999-08-23 22:48  jrandom

            * README (1.5): [no log message]

         1999-08-22 19:34  jrandom

            * README (1.4): trivial change
         ...
         floss$

The first entry shows that four files were committed at once, with the log message, "Committing from pcl-cvs 2.9, just for kicks.". (The -r option was used to show the revision number of each file associated with that log message.)

Like CVS itself, cvs2cl.pl takes the current directory as an implied argument but acts on individual files if given file name arguments. Following are a few of the most commonly used options.

- `h`, `--help`

  Show usage (including a complete list of options).

- `-r`, `--revisions`

  Show revision numbers in output. If used in conjunction with -b, branches are shown as BRANCHNAME.N, where N is the revision on the branch.

- `-t`, `--tags`

  Show tags (symbolic names) for revisions that have them.

- `-b`, `--branches`

  Show the branch name for revisions on that branch. (See also -r.)

- `-g OPTS`, `--global-opts OPTS`

  Pass OPTS as global arguments to cvs. Internally, cvs2cl.pl invokes cvs to get the raw log data; thus, OPTS are passed right after the cvs in that invocation. For example, to achieve quiet behavior and compression, you can do this:

                floss$ cvs2cl.pl -g "-Q -z3"

- `-l OPTS`, `--log-opts OPTS`

  Similar to -g, except that OPTS are passed as command options instead of global options. To generate a ChangeLog showing only commits that happened between July 26 and August 15, you can do this:

                floss$ cvs2cl.pl -l "'-d1999-07-26<1999-08-15'"

  Notice the double-layered quoting - this is necessary in Unix because the shell that invokes cvs log (inside cvs2cl.pl) interprets the `<` as a shell redirection symbol. Therefore, the quotes have to be passed as part of the argument, making it necessary to surround the whole thing with an additional set of quotes.

- `-d`, `--distributed`

  Put an individual ChangeLog in each subdirectory, covering only commits in that subdirectory (as opposed to building one ChangeLog that covers the directory where cvs2cl.pl was invoked and all subdirectories underneath it).

Node: cvsq -- Queue CVS Commands For Later Connection, Next: Other Packages, Previous: cvslock -- Lock Repositories For Atomicity, Up: Third-Party Tools

### cvsq - Queue CVS Commands For Later Connection

Depends on: Bash

URL: http://www.volny.cz/v.slavik/lt/cvsq.html

Vaclav Slavik <v.slavik@volny.cz>, the author of cvsq, has this to say about it:

cvsq stands for "cvs queued" and it is a small bash script that wraps around CVS. It makes working with CVS repository a bit easier for people connected via dial-up, because it can queue CVS commands and pass them to "real cvs" later.

For example, you can commit files immediately after editing them, when being offline, so you don't forget about them:

             cvsq commit -m "change 1" file1.c
             cvsq commit -m "change 2" file2.c
             cvsq commit -m "change 3" file3.c

And then, when you go online, you simply type

             cvsq upload

and all changes will be commited into the repository. If uploading of a particular file fails, it won't be lost - instead, you'll see error message and the file will stay in cvsq queue.

You can use cvsq even for commands that make no sense when offline - in that case, the command is immediately passed to cvs and not queued. For example, you can call cvsq update and it won't be put into the queue but executed immediately. In fact, you can start using cvsq as a replacement for cvs.

cvsq is in public domain.

Node: cvslock -- Lock Repositories For Atomicity, Next: cvsq -- Queue CVS Commands For Later Connection, Previous: cvs2cl -- Generate GNU-Style ChangeLogs, Up: Third-Party Tools

### cvslock - Lock Repositories For Atomicity

Depends on: C compiler for installation; nothing for runtime

URL: ftp://riemann.iam.uni-bonn.de/pub/users/roessler/cvslock/

This program locks a CVS repository (either for reading or writing) in the same way that CVS does, so that CVS will honor the locks. This can be useful when, for example, you need to make a copy of the whole repository and want to avoid catching parts of commits or other people's lockfiles.

The cvslock distribution is packaged extremely well and can be installed according to the usual GNU procedures. Here's a transcript of an install session:

         floss$ zcat cvslock-0.1.tar.gz | tar xvf -
         cvslock-0.1/
         cvslock-0.1/Makefile.in
         cvslock-0.1/README
         cvslock-0.1/COPYING
         cvslock-0.1/Makefile.am
         cvslock-0.1/acconfig.h
         cvslock-0.1/aclocal.m4
         cvslock-0.1/config.h.in
         cvslock-0.1/configure
         cvslock-0.1/configure.in
         cvslock-0.1/install-sh
         cvslock-0.1/missing
         cvslock-0.1/mkinstalldirs
         cvslock-0.1/stamp-h.in
         cvslock-0.1/cvslock.c
         cvslock-0.1/cvslock.1
         cvslock-0.1/snprintf.c
         cvslock-0.1/cvslssh
         cvslock-0.1/VERSION
         floss$ cd cvslock-0.1
         floss$ ./configure
          ...
         floss$ make
         gcc -DHAVE_CONFIG_H -I. -I. -I.   -g -O2 -c cvslock.c
         gcc -g -O2  -o cvslock  cvslock.o
         floss$ make install
          ...
         floss$

(Note that you may have to do the make install step as root).

Now, cvslock is installed as /usr/local/bin/cvslock. When you invoke it, you can specify the repository with -d or via the $CVSROOT environment variable, just as with CVS itself (the following examples use -d). Its only required argument is the name of the directory to lock, relative to the top of the repository. That directory and all of its subdirectories will be locked. In this example, there are no subdirectories, so only one lockfile is created:

         floss$ ls /usr/local/newrepos/myproj/b-subdir/
         random.c,v
         floss$ cvslock -d /usr/local/newrepos  myproj/b-subdir
         floss$ ls /usr/local/newrepos/myproj/b-subdir/
         #cvs.rfl.cvslock.floss.27378  random.c,v
         floss$ cvslock -u -p 27378 -d /usr/local/newrepos  myproj/b-subdir
         floss$ ls /usr/local/newrepos/myproj/b-subdir/
         random.c,v
         floss$

Notice that when I cleared the lock (-u for `unlock`), I had to specify `-p 27378`. That's because cvslock uses Unix process IDs when creating lockfile names to ensure that its locks are unique. When you unlock, you have to tell cvslock which lock instance to remove, even if there's only one instance present. Thus, the -p flag tells cvslock which previous instance of itself it's cleaning up after (you can use -p with or without -u, though).

If you're going to be working in the repository for a while, doing various operations directly in the file system, you can use the -s option to have cvslock start up a new shell for you. It then consults the `$SHELL` environment variable in your current shell to determine which shell to use:

         floss$ cvslock -s -d /usr/local/newrepos myproj

The locks remain present until you exit the shell, at which time they are automatically removed. You can also use the -c option to execute a command while the repository is locked. Just as with -s, the locks are put in place before the command starts and removed when it's finished. In the following example, we lock the repository just long enough to display a listing of all of the lockfiles:

         floss$ cvslock -c 'find . -name "*cvslock*" ' -d /usr/local/newrepos myproj
         cvslock: '/usr/local/newrepos/myproj' locked successfully.
         cvslock: Starting 'find . -name "*cvslock*" -print'...
         ./a-subdir/subsubdir/#cvs.rfl.cvslock.floss.27452
         ./a-subdir/#cvs.rfl.cvslock.floss.27452
         ./b-subdir/#cvs.rfl.cvslock.floss.27452
         ./#cvs.rfl.cvslock.floss.27452
         floss$ find /usr/local/newrepos/myproj -name "*cvslock*" -print
         floss$

The command (the argument to the -c option) is run with the specified repository directory as its working directory.

By default, cvslock creates read-locks. You can tell it to use write-locks instead by passing the -W option. (You can pass -R to specify read-locks, but that's the default anyway.) Always remove any locks when you're finished, so that other users' CVS processes don't wait needlessly.

Note that cvslock must be run on the machine where the repository resides - you cannot specify a remote repository. (For more information, run `man cvslock`, which is a manual page installed when you ran `make install`.)

Node: Other Packages, Next: Writing Your Own Tools, Previous: cvsq -- Queue CVS Commands For Later Connection, Up: Third-Party Tools

### Other Packages

Many other third-party packages are available for CVS. Following are pointers to some of these.

### CVSUp (Part Of The FreeBSD Project)

CVSUp is an efficient generic mirroring tool with special built-in support for mirroring CVS repositories. The FreeBSD operating system uses it to distribute changes from their master repository, so users can keep up to date conveniently.

For more information on CVSUp in general, check out http://www.polstra.com/projects/freeware/CVSup/.

For its use in FreeBSD in particular, see http://www.freebsd.org/handbook/synching.html#CVSUP.

### CVSWeb: A Web Interface To CVS Repositories

CVSWeb provides a Web interface to browsing CVS repositories. A more accurate name might be "RCSWeb", because what it actually does is allow you to browse revisions directly in a repository, viewing log messages and diffs. Although I've never found it to be a particularly compelling interface myself, I have to admit that it is intuitive enough and a lot of sites use it.

Although the software was originally written by Bill Fenner, the version most actively under development right now seems to be Henner Zeller's, at http://linux.fh-heilbronn.de/~zeller/cgi/cvsweb.cgi/.

You may also want to visit Fenner's original site at http://www.freebsd.org/~fenner/cvsweb/ and possibly this summary of the CVSWeb scene at http://www.cvshome.org/dev/addoncvsweb.html.

Finally, if you'd like to see CVSWeb in action, a good example can be browsed at http://sourceware.cygnus.com/cgi-bin/cvsweb.cgi/.

### The CVS contrib/ Directory

As mentioned in Repository Administration, a number of third-party tools are shipped with CVS and are collected in the contrib/ directory. Although I'm not aware of any formal rule for determining which tools are distributed with CVS, an effort may be in process to gather most of the widely used third-party tools and put them in contrib/ so people know where to find them. Until that happens, the best way to find such tools is to look in contrib/, look at various CVS Web sites, and ask on the mailing list.

Node: Writing Your Own Tools, Previous: Other Packages, Up: Third-Party Tools

### Writing Your Own Tools

CVS can at times seem like a bewildering collection of improvised standards. There's RCS format, various output formats (history, annotate, log, update, and so on), several repository administrative file formats, working copy administrative file formats, the client/server protocol, the lockfile protocol.... (Are you numb yet? I could keep going, you know.)

Fortunately, these standards remain fairly consistent from release to release - so if you're trying to write a tool to work with CVS, you at least don't have to worry about hitting a moving target. For every internal standard, there are usually a few people on the info-cvs@gnu.org mailing list who know it extremely well (several of them helped me out during the writing of this book). There is also the documentation that comes with the CVS distribution (especially doc/cvs.texinfo, doc/cvsclient.texi, and doc/RCSFILES). Finally, there is the CVS source code itself, the last word on any question of implementation or behavior.

With all of this at your disposal, there's no reason to hesitate. If you can think of some utility that would make your life with CVS easier, go ahead and write it - chances are other people have been wanting it, too. Unlike a change to CVS itself, a small, standalone external utility can get wide distribution very quickly, resulting in quicker feedback for its author and faster bug fixes for all of the users.

Node: Index, Next: GNU General Public License, Previous: Third-Party Tools, Up: Top

## Index

Sorry, the index is still in progress.

Since the online format is searchable anyway, I decided the incompleteness of the index need not delay the release of the chapters. I hope to have the index finished reasonably soon. Volunteer indexers are certainly welcome, too - please email bug-cvsbook@red-bean.com if you're interested.

Node: GNU General Public License, Next: GNU Free Documentation License, Previous: Index, Up: Top

## GNU General Public License

         GNU General Public License

         Version 2, June 1991

         Copyright (C) 1989, 1991 Free Software Foundation, Inc.
         59 Temple Place - Suite 330, Boston, MA  02111-1307, USA

         Everyone is permitted to copy and distribute verbatim copies
         of this license document, but changing it is not allowed.

         Preamble

         The licenses for most software are designed to take away your freedom to
         share and change it. By contrast, the GNU General Public License is intended
         to guarantee your freedom to share and change free software--to make sure
         the software is free for all its users. This General Public License applies
         to most of the Free Software Foundation's software and to any other program
         whose authors commit to using it. (Some other Free Software Foundation
         software is covered by the GNU Library General Public License instead.) You
         can apply it to your programs, too.

         When we speak of free software, we are referring to freedom, not price. Our
         General Public Licenses are designed to make sure that you have the freedom
         to distribute copies of free software (and charge for this service if you
         wish), that you receive source code or can get it if you want it, that you
         can change the software or use pieces of it in new free programs; and that
         you know you can do these things.

         To protect your rights, we need to make restrictions that forbid anyone to
         deny you these rights or to ask you to surrender the rights. These
         restrictions translate to certain responsibilities for you if you distribute
         copies of the software, or if you modify it.

         For example, if you distribute copies of such a program, whether gratis or
         for a fee, you must give the recipients all the rights that you have. You
         must make sure that they, too, receive or can get the source code. And you
         must show them these terms so they know their rights.

         We protect your rights with two steps: (1) copyright the software, and (2)
         offer you this license which gives you legal permission to copy, distribute
         and/or modify the software.

         Also, for each author's protection and ours, we want to make certain that
         everyone understands that there is no warranty for this free software. If
         the software is modified by someone else and passed on, we want its
         recipients to know that what they have is not the original, so that any
         problems introduced by others will not reflect on the original authors'
         reputations.

         Finally, any free program is threatened constantly by software patents. We
         wish to avoid the danger that redistributors of a free program will
         individually obtain patent licenses, in effect making the program
         proprietary. To prevent this, we have made it clear that any patent must be
         licensed for everyone's free use or not licensed at all.

         The precise terms and conditions for copying, distribution and modification
         follow.

         TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

         0. This License applies to any program or other work which contains a notice
         placed by the copyright holder saying it may be distributed under the terms
         of this General Public License. The "Program", below, refers to any such
         program or work, and a "work based on the Program" means either the Program
         or any derivative work under copyright law: that is to say, a work
         containing the Program or a portion of it, either verbatim or with
         modifications and/or translated into another language. (Hereinafter,
         translation is included without limitation in the term "modification".) Each
         licensee is addressed as "you".

         Activities other than copying, distribution and modification are not covered
         by this License; they are outside its scope. The act of running the Program
         is not restricted, and the output from the Program is covered only if its
         contents constitute a work based on the Program (independent of having been
         made by running the Program). Whether that is true depends on what the
         Program does.

         1. You may copy and distribute verbatim copies of the Program's source code
         as you receive it, in any medium, provided that you conspicuously and
         appropriately publish on each copy an appropriate copyright notice and
         disclaimer of warranty; keep intact all the notices that refer to this
         License and to the absence of any warranty; and give any other recipients of
         the Program a copy of this License along with the Program.

         You may charge a fee for the physical act of transferring a copy, and you
         may at your option offer warranty protection in exchange for a fee.

         2. You may modify your copy or copies of the Program or any portion of it,
         thus forming a work based on the Program, and copy and distribute such
         modifications or work under the terms of Section 1 above, provided that you
         also meet all of these conditions:

            * a) You must cause the modified files to carry prominent notices stating
              that you changed the files and the date of any change.

            * b) You must cause any work that you distribute or publish, that in
              whole or in part contains or is derived from the Program or any part
              thereof, to be licensed as a whole at no charge to all third parties
              under the terms of this License.

            * c) If the modified program normally reads commands interactively when
              run, you must cause it, when started running for such interactive use
              in the most ordinary way, to print or display an announcement including
              an appropriate copyright notice and a notice that there is no warranty
              (or else, saying that you provide a warranty) and that users may
              redistribute the program under these conditions, and telling the user
              how to view a copy of this License. (Exception: if the Program itself
              is interactive but does not normally print such an announcement, your
              work based on the Program is not required to print an announcement.)

         These requirements apply to the modified work as a whole. If identifiable
         sections of that work are not derived from the Program, and can be
         reasonably considered independent and separate works in themselves, then
         this License, and its terms, do not apply to those sections when you
         distribute them as separate works. But when you distribute the same sections
         as part of a whole which is a work based on the Program, the distribution of
         the whole must be on the terms of this License, whose permissions for other
         licensees extend to the entire whole, and thus to each and every part
         regardless of who wrote it.

         Thus, it is not the intent of this section to claim rights or contest your
         rights to work written entirely by you; rather, the intent is to exercise
         the right to control the distribution of derivative or collective works
         based on the Program.

         In addition, mere aggregation of another work not based on the Program with
         the Program (or with a work based on the Program) on a volume of a storage
         or distribution medium does not bring the other work under the scope of this
         License.

         3. You may copy and distribute the Program (or a work based on it, under
         Section 2) in object code or executable form under the terms of Sections 1
         and 2 above provided that you also do one of the following:

            * a) Accompany it with the complete corresponding machine-readable source
              code, which must be distributed under the terms of Sections 1 and 2
              above on a medium customarily used for software interchange; or,

            * b) Accompany it with a written offer, valid for at least three years,
              to give any third party, for a charge no more than your cost of
              physically performing source distribution, a complete machine-readable
              copy of the corresponding source code, to be distributed under the
              terms of Sections 1 and 2 above on a medium customarily used for
              software interchange; or,

            * c) Accompany it with the information you received as to the offer to
              distribute corresponding source code. (This alternative is allowed only
              for noncommercial distribution and only if you received the program in
              object code or executable form with such an offer, in accord with
              Subsection b above.)

         The source code for a work means the preferred form of the work for making
         modifications to it. For an executable work, complete source code means all
         the source code for all modules it contains, plus any associated interface
         definition files, plus the scripts used to control compilation and
         installation of the executable. However, as a special exception, the source
         code distributed need not include anything that is normally distributed (in
         either source or binary form) with the major components (compiler, kernel,
         and so on) of the operating system on which the executable runs, unless that
         component itself accompanies the executable.

         If distribution of executable or object code is made by offering access to
         copy from a designated place, then offering equivalent access to copy the
         source code from the same place counts as distribution of the source code,
         even though third parties are not compelled to copy the source along with
         the object code.

         4. You may not copy, modify, sublicense, or distribute the Program except as
         expressly provided under this License. Any attempt otherwise to copy,
         modify, sublicense or distribute the Program is void, and will automatically
         terminate your rights under this License. However, parties who have received
         copies, or rights, from you under this License will not have their licenses
         terminated so long as such parties remain in full compliance.

         5. You are not required to accept this License, since you have not signed
         it. However, nothing else grants you permission to modify or distribute the
         Program or its derivative works. These actions are prohibited by law if you
         do not accept this License. Therefore, by modifying or distributing the
         Program (or any work based on the Program), you indicate your acceptance of
         this License to do so, and all its terms and conditions for copying,
         distributing or modifying the Program or works based on it.

         6. Each time you redistribute the Program (or any work based on the
         Program), the recipient automatically receives a license from the original
         licensor to copy, distribute or modify the Program subject to these terms
         and conditions. You may not impose any further restrictions on the
         recipients' exercise of the rights granted herein. You are not responsible
         for enforcing compliance by third parties to this License.

         7. If, as a consequence of a court judgment or allegation of patent
         infringement or for any other reason (not limited to patent issues),
         conditions are imposed on you (whether by court order, agreement or
         otherwise) that contradict the conditions of this License, they do not
         excuse you from the conditions of this License. If you cannot distribute so
         as to satisfy simultaneously your obligations under this License and any
         other pertinent obligations, then as a consequence you may not distribute
         the Program at all. For example, if a patent license would not permit
         royalty-free redistribution of the Program by all those who receive copies
         directly or indirectly through you, then the only way you could satisfy both
         it and this License would be to refrain entirely from distribution of the
         Program.

         If any portion of this section is held invalid or unenforceable under any
         particular circumstance, the balance of the section is intended to apply and
         the section as a whole is intended to apply in other circumstances.

         It is not the purpose of this section to induce you to infringe any patents
         or other property right claims or to contest validity of any such claims;
         this section has the sole purpose of protecting the integrity of the free
         software distribution system, which is implemented by public license
         practices. Many people have made generous contributions to the wide range of
         software distributed through that system in reliance on consistent
         application of that system; it is up to the author/donor to decide if he or
         she is willing to distribute software through any other system and a
         licensee cannot impose that choice.

         This section is intended to make thoroughly clear what is believed to be a
         consequence of the rest of this License.

         8. If the distribution and/or use of the Program is restricted in certain
         countries either by patents or by copyrighted interfaces, the original
         copyright holder who places the Program under this License may add an
         explicit geographical distribution limitation excluding those countries, so
         that distribution is permitted only in or among countries not thus excluded.
         In such case, this License incorporates the limitation as if written in the
         body of this License.

         9. The Free Software Foundation may publish revised and/or new versions of
         the General Public License from time to time. Such new versions will be
         similar in spirit to the present version, but may differ in detail to
         address new problems or concerns.

         Each version is given a distinguishing version number. If the Program
         specifies a version number of this License which applies to it and "any
         later version", you have the option of following the terms and conditions
         either of that version or of any later version published by the Free
         Software Foundation. If the Program does not specify a version number of
         this License, you may choose any version ever published by the Free Software
         Foundation.

         10. If you wish to incorporate parts of the Program into other free programs
         whose distribution conditions are different, write to the author to ask for
         permission. For software which is copyrighted by the Free Software
         Foundation, write to the Free Software Foundation; we sometimes make
         exceptions for this. Our decision will be guided by the two goals of
         preserving the free status of all derivatives of our free software and of
         promoting the sharing and reuse of software generally.

         NO WARRANTY

         11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR
         THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
         OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
         PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
         OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
         MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO
         THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM
         PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR
         CORRECTION.

         12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
         WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
         REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
         INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
         OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO
         LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR
         THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
         PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
         POSSIBILITY OF SUCH DAMAGES.

         END OF TERMS AND CONDITIONS

         How to Apply These Terms to Your New Programs

         If you develop a new program, and you want it to be of the greatest possible
         use to the public, the best way to achieve this is to make it free software
         which everyone can redistribute and change under these terms.

         To do so, attach the following notices to the program. It is safest to
         attach them to the start of each source file to most effectively convey the
         exclusion of warranty; and each file should have at least the "copyright"
         line and a pointer to where the full notice is found.

         one line to give the program's name and an idea of what it does.
         Copyright (C) yyyy  name of author

         This program is free software; you can redistribute it and/or
         modify it under the terms of the GNU General Public License
         as published by the Free Software Foundation; either version 2
         of the License, or (at your option) any later version.

         This program is distributed in the hope that it will be useful,
         but WITHOUT ANY WARRANTY; without even the implied warranty of
         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
         GNU General Public License for more details.

         You should have received a copy of the GNU General Public License
         along with this program; if not, write to the Free Software
         Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

         Also add information on how to contact you by electronic and paper mail.

         If the program is interactive, make it output a short notice like this when
         it starts in an interactive mode:

         Gnomovision version 69, Copyright (C) yyyy name of author
         Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
         type `show w'.  This is free software, and you are welcome
         to redistribute it under certain conditions; type `show c'
         for details.

         The hypothetical commands `show w' and `show c' should show the appropriate
         parts of the General Public License. Of course, the commands you use may be
         called something other than `show w' and `show c'; they could even be
         mouse-clicks or menu items--whatever suits your program.

         You should also get your employer (if you work as a programmer) or your
         school, if any, to sign a "copyright disclaimer" for the program, if
         necessary. Here is a sample; alter the names:

         Yoyodyne, Inc., hereby disclaims all copyright
         interest in the program `Gnomovision'
         (which makes passes at compilers) written
         by James Hacker.

         signature of Ty Coon, 1 April 1989
         Ty Coon, President of Vice

         This General Public License does not permit incorporating your program into
         proprietary programs. If your program is a subroutine library, you may
         consider it more useful to permit linking proprietary applications with the
         library. If this is what you want to do, use the GNU Library General Public
         License instead of this License.

Node: GNU Free Documentation License, Previous: GNU General Public License, Up: Top

## GNU Free Documentation License

         GNU Free Documentation License

         Version 1.1, March 2000

         Copyright (C) 2000  Free Software Foundation, Inc.
         59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
         Everyone is permitted to copy and distribute verbatim copies
         of this license document, but changing it is not allowed.

         0. PREAMBLE

         The purpose of this License is to make a manual, textbook, or other written
         document "free" in the sense of freedom: to assure everyone the effective
         freedom to copy and redistribute it, with or without modifying it, either
         commercially or noncommercially. Secondarily, this License preserves for the
         author and publisher a way to get credit for their work, while not being
         considered responsible for modifications made by others.

         This License is a kind of "copyleft", which means that derivative works of
         the document must themselves be free in the same sense. It complements the
         GNU General Public License, which is a copyleft license designed for free
         software.

         We have designed this License in order to use it for manuals for free
         software, because free software needs free documentation: a free program
         should come with manuals providing the same freedoms that the software does.
         But this License is not limited to software manuals; it can be used for any
         textual work, regardless of subject matter or whether it is published as a
         printed book. We recommend this License principally for works whose purpose
         is instruction or reference.

         1. APPLICABILITY AND DEFINITIONS

         This License applies to any manual or other work that contains a notice
         placed by the copyright holder saying it can be distributed under the terms
         of this License. The "Document", below, refers to any such manual or work.
         Any member of the public is a licensee, and is addressed as "you".

         A "Modified Version" of the Document means any work containing the Document
         or a portion of it, either copied verbatim, or with modifications and/or
         translated into another language.

         A "Secondary Section" is a named appendix or a front-matter section of the
         Document that deals exclusively with the relationship of the publishers or
         authors of the Document to the Document's overall subject (or to related
         matters) and contains nothing that could fall directly within that overall
         subject. (For example, if the Document is in part a textbook of mathematics,
         a Secondary Section may not explain any mathematics.) The relationship could
         be a matter of historical connection with the subject or with related
         matters, or of legal, commercial, philosophical, ethical or political
         position regarding them.

         The "Invariant Sections" are certain Secondary Sections whose titles are
         designated, as being those of Invariant Sections, in the notice that says
         that the Document is released under this License.

         The "Cover Texts" are certain short passages of text that are listed, as
         Front-Cover Texts or Back-Cover Texts, in the notice that says that the
         Document is released under this License.

         A "Transparent" copy of the Document means a machine-readable copy,
         represented in a format whose specification is available to the general
         public, whose contents can be viewed and edited directly and
         straightforwardly with generic text editors or (for images composed of
         pixels) generic paint programs or (for drawings) some widely available
         drawing editor, and that is suitable for input to text formatters or for
         automatic translation to a variety of formats suitable for input to text
         formatters. A copy made in an otherwise Transparent file format whose markup
         has been designed to thwart or discourage subsequent modification by readers
         is not Transparent. A copy that is not "Transparent" is called "Opaque".

         Examples of suitable formats for Transparent copies include plain ASCII
         without markup, Texinfo input format, LaTeX input format, SGML or XML using
         a publicly available DTD, and standard-conforming simple HTML designed for
         human modification. Opaque formats include PostScript, PDF, proprietary
         formats that can be read and edited only by proprietary word processors,
         SGML or XML for which the DTD and/or processing tools are not generally
         available, and the machine-generated HTML produced by some word processors
         for output purposes only.

         The "Title Page" means, for a printed book, the title page itself, plus such
         following pages as are needed to hold, legibly, the material this License
         requires to appear in the title page. For works in formats which do not have
         any title page as such, "Title Page" means the text near the most prominent
         appearance of the work's title, preceding the beginning of the body of the
         text.

         2. VERBATIM COPYING

         You may copy and distribute the Document in any medium, either commercially
         or noncommercially, provided that this License, the copyright notices, and
         the license notice saying this License applies to the Document are
         reproduced in all copies, and that you add no other conditions whatsoever to
         those of this License. You may not use technical measures to obstruct or
         control the reading or further copying of the copies you make or distribute.
         However, you may accept compensation in exchange for copies. If you
         distribute a large enough number of copies you must also follow the
         conditions in section 3.

         You may also lend copies, under the same conditions stated above, and you
         may publicly display copies.

         3. COPYING IN QUANTITY

         If you publish printed copies of the Document numbering more than 100, and
         the Document's license notice requires Cover Texts, you must enclose the
         copies in covers that carry, clearly and legibly, all these Cover Texts:
         Front-Cover Texts on the front cover, and Back-Cover Texts on the back
         cover. Both covers must also clearly and legibly identify you as the
         publisher of these copies. The front cover must present the full title with
         all words of the title equally prominent and visible. You may add other
         material on the covers in addition. Copying with changes limited to the
         covers, as long as they preserve the title of the Document and satisfy these
         conditions, can be treated as verbatim copying in other respects.

         If the required texts for either cover are too voluminous to fit legibly,
         you should put the first ones listed (as many as fit reasonably) on the
         actual cover, and continue the rest onto adjacent pages.

         If you publish or distribute Opaque copies of the Document numbering more
         than 100, you must either include a machine-readable Transparent copy along
         with each Opaque copy, or state in or with each Opaque copy a
         publicly-accessible computer-network location containing a complete
         Transparent copy of the Document, free of added material, which the general
         network-using public has access to download anonymously at no charge using
         public-standard network protocols. If you use the latter option, you must
         take reasonably prudent steps, when you begin distribution of Opaque copies
         in quantity, to ensure that this Transparent copy will remain thus
         accessible at the stated location until at least one year after the last
         time you distribute an Opaque copy (directly or through your agents or
         retailers) of that edition to the public.

         It is requested, but not required, that you contact the authors of the
         Document well before redistributing any large number of copies, to give them
         a chance to provide you with an updated version of the Document.

         4. MODIFICATIONS

         You may copy and distribute a Modified Version of the Document under the
         conditions of sections 2 and 3 above, provided that you release the Modified
         Version under precisely this License, with the Modified Version filling the
         role of the Document, thus licensing distribution and modification of the
         Modified Version to whoever possesses a copy of it. In addition, you must do
         these things in the Modified Version:

            * A. Use in the Title Page (and on the covers, if any) a title distinct
              from that of the Document, and from those of previous versions (which
              should, if there were any, be listed in the History section of the
              Document). You may use the same title as a previous version if the
              original publisher of that version gives permission.
            * B. List on the Title Page, as authors, one or more persons or entities
              responsible for authorship of the modifications in the Modified
              Version, together with at least five of the principal authors of the
              Document (all of its principal authors, if it has less than five).
            * C. State on the Title page the name of the publisher of the Modified
              Version, as the publisher.
            * D. Preserve all the copyright notices of the Document.
            * E. Add an appropriate copyright notice for your modifications adjacent
              to the other copyright notices.
            * F. Include, immediately after the copyright notices, a license notice
              giving the public permission to use the Modified Version under the
              terms of this License, in the form shown in the Addendum below.
            * G. Preserve in that license notice the full lists of Invariant Sections
              and required Cover Texts given in the Document's license notice.
            * H. Include an unaltered copy of this License.
            * I. Preserve the section entitled "History", and its title, and add to
              it an item stating at least the title, year, new authors, and publisher
              of the Modified Version as given on the Title Page. If there is no
              section entitled "History" in the Document, create one stating the
              title, year, authors, and publisher of the Document as given on its
              Title Page, then add an item describing the Modified Version as stated
              in the previous sentence.
            * J. Preserve the network location, if any, given in the Document for
              public access to a Transparent copy of the Document, and likewise the
              network locations given in the Document for previous versions it was
              based on. These may be placed in the "History" section. You may omit a
              network location for a work that was published at least four years
              before the Document itself, or if the original publisher of the version
              it refers to gives permission.
            * K. In any section entitled "Acknowledgements" or "Dedications",
              preserve the section's title, and preserve in the section all the
              substance and tone of each of the contributor acknowledgements and/or
              dedications given therein.
            * L. Preserve all the Invariant Sections of the Document, unaltered in
              their text and in their titles. Section numbers or the equivalent are
              not considered part of the section titles.
            * M. Delete any section entitled "Endorsements". Such a section may not
              be included in the Modified Version.
            * N. Do not retitle any existing section as "Endorsements" or to conflict
              in title with any Invariant Section.

         If the Modified Version includes new front-matter sections or appendices
         that qualify as Secondary Sections and contain no material copied from the
         Document, you may at your option designate some or all of these sections as
         invariant. To do this, add their titles to the list of Invariant Sections in
         the Modified Version's license notice. These titles must be distinct from
         any other section titles.

         You may add a section entitled "Endorsements", provided it contains nothing
         but endorsements of your Modified Version by various parties--for example,
         statements of peer review or that the text has been approved by an
         organization as the authoritative definition of a standard.

         You may add a passage of up to five words as a Front-Cover Text, and a
         passage of up to 25 words as a Back-Cover Text, to the end of the list of
         Cover Texts in the Modified Version. Only one passage of Front-Cover Text
         and one of Back-Cover Text may be added by (or through arrangements made by)
         any one entity. If the Document already includes a cover text for the same
         cover, previously added by you or by arrangement made by the same entity you
         are acting on behalf of, you may not add another; but you may replace the
         old one, on explicit permission from the previous publisher that added the
         old one.

         The author(s) and publisher(s) of the Document do not by this License give
         permission to use their names for publicity for or to assert or imply
         endorsement of any Modified Version.

         5. COMBINING DOCUMENTS

         You may combine the Document with other documents released under this
         License, under the terms defined in section 4 above for modified versions,
         provided that you include in the combination all of the Invariant Sections
         of all of the original documents, unmodified, and list them all as Invariant
         Sections of your combined work in its license notice.

         The combined work need only contain one copy of this License, and multiple
         identical Invariant Sections may be replaced with a single copy. If there
         are multiple Invariant Sections with the same name but different contents,
         make the title of each such section unique by adding at the end of it, in
         parentheses, the name of the original author or publisher of that section if
         known, or else a unique number. Make the same adjustment to the section
         titles in the list of Invariant Sections in the license notice of the
         combined work.

         In the combination, you must combine any sections entitled "History" in the
         various original documents, forming one section entitled "History"; likewise
         combine any sections entitled "Acknowledgements", and any sections entitled
         "Dedications". You must delete all sections entitled "Endorsements."

         6. COLLECTIONS OF DOCUMENTS

         You may make a collection consisting of the Document and other documents
         released under this License, and replace the individual copies of this
         License in the various documents with a single copy that is included in the
         collection, provided that you follow the rules of this License for verbatim
         copying of each of the documents in all other respects.

         You may extract a single document from such a collection, and distribute it
         individually under this License, provided you insert a copy of this License
         into the extracted document, and follow this License in all other respects
         regarding verbatim copying of that document.

         7. AGGREGATION WITH INDEPENDENT WORKS

         A compilation of the Document or its derivatives with other separate and
         independent documents or works, in or on a volume of a storage or
         distribution medium, does not as a whole count as a Modified Version of the
         Document, provided no compilation copyright is claimed for the compilation.
         Such a compilation is called an "aggregate", and this License does not apply
         to the other self-contained works thus compiled with the Document, on
         account of their being thus compiled, if they are not themselves derivative
         works of the Document. If the Cover Text requirement of section 3 is
         applicable to these copies of the Document, then if the Document is less
         than one quarter of the entire aggregate, the Document's Cover Texts may be
         placed on covers that surround only the Document within the aggregate.
         Otherwise they must appear on covers around the whole aggregate.

         8. TRANSLATION

         Translation is considered a kind of modification, so you may distribute
         translations of the Document under the terms of section 4. Replacing
         Invariant Sections with translations requires special permission from their
         copyright holders, but you may include translations of some or all Invariant
         Sections in addition to the original versions of these Invariant Sections.
         You may include a translation of this License provided that you also include
         the original English version of this License. In case of a disagreement
         between the translation and the original English version of this License,
         the original English version will prevail.

         9. TERMINATION

         You may not copy, modify, sublicense, or distribute the Document except as
         expressly provided for under this License. Any other attempt to copy,
         modify, sublicense or distribute the Document is void, and will
         automatically terminate your rights under this License. However, parties who
         have received copies, or rights, from you under this License will not have
         their licenses terminated so long as such parties remain in full compliance.

         10. FUTURE REVISIONS OF THIS LICENSE

         The Free Software Foundation may publish new, revised versions of the GNU
         Free Documentation License from time to time. Such new versions will be
         similar in spirit to the present version, but may differ in detail to
         address new problems or concerns. See http://www.gnu.org/copyleft/.

         Each version of the License is given a distinguishing version number. If the
         Document specifies that a particular numbered version of this License "or
         any later version" applies to it, you have the option of following the terms
         and conditions either of that specified version or of any later version that
         has been published (not as a draft) by the Free Software Foundation. If the
         Document does not specify a version number of this License, you may choose
         any version ever published (not as a draft) by the Free Software Foundation.

         How to use this License for your documents

         To use this License in a document you have written, include a copy of the
         License in the document and put the following copyright and license notices
         just after the title page:

               Copyright (c)  YEAR  YOUR NAME.
               Permission is granted to copy, distribute and/or modify this document
               under the terms of the GNU Free Documentation License, Version 1.1
               or any later version published by the Free Software Foundation;
               with the Invariant Sections being LIST THEIR TITLES, with the
               Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
               A copy of the license is included in the section entitled "GNU
               Free Documentation License".

         If you have no Invariant Sections, write "with no Invariant Sections"
         instead of saying which ones are invariant. If you have no Front-Cover
         Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being
         LIST"; likewise for Back-Cover Texts.

         If your document contains nontrivial examples of program code, we recommend
         releasing these examples in parallel under your choice of free software
         license, such as the GNU General Public License, to permit their use in free
         software.