Virecover is a program which extracts the most recent version of a text file
from a temporary file in /usr/tmp.

When you edit a file with Elvis, only about 5K bytes of the file are stored
in RAM; the rest is stored in a file in /usr/tmp.  This allows you to edit
files larger than a process' data space.  It also plays a big part in the
way that "undo" and "paste" were implemented.

The virecover program basically extracts the "undo" version from the file.
This is most useful when the system (or Elvis) crashes in the middle of a
long edit session, because the "undo" version of the file contains all but
your last change.  Nearly all of your work can be salvaged.

There are two ways to invoke virecover:

	virecover textfilename
	virecover </usr/tmp/viname

The first way is the most common.  You just give virecover the name of the file
you were editing, and it finds the matching file in /usr/tmp and writes the
newest available version of the file over the current version.  It then
deletes the /usr/tmp file.

The other way, where you redirect its stdin to come from a particular /usr/tmp
file, is used when you have either
	- forgotten which file that is & you want to see its contents, or
	- when you want to recover the file, without losing either the /usr/tmp
	  file or the current version of the text file.
