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Release Notes

Read the CHANGES document included in the distribution for a more complete
summary of changes to MHonArc. This document highlights important changes
that have occurred and important usage details which you should be aware of
before using MHonArc. If you are upgrading from a previous release, make
sure to check for the highlighted incompatibilites from earlier releases.

  * Compatibility Notes
      + UPGRADING FROM v2.4.x OR EARLIER: DEFRCNAME Change
      + UPGRADING FROM v2.4.x OR EARLIER: HEADER and FOOTER Removed
      + UPGRADING FROM v2.4.x OR EARLIER: MIMEFILTERS API Change
      + UPGRADING FROM v2.1.x OR EARLIER: Database Format Change
      + DOWNGRADING TO OLDER VERSIONS
  * General Notes

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Compatibility Notes

This sections provides notes dealing with compatibility issues if upgrading
from a previous release of MHonArc:

UPGRADING FROM v2.4.x OR EARLIER: DEFRCNAME Change

The default value for the DEFRCNAME is now called ".mhonarc.mrc", or
"mhonarc.mrc" under Windows and VMS. The old value was ".mhonarc.rc", or
"mhonarc.rc". If you use the default resource file, you will need to rename
the file to match the filenames used for v2.5 and later.

UPGRADING FROM v2.4.x OR EARLIER: HEADER and FOOTER Removed

The HEADER and FOOTER resources are no longer supported. If you are using
these resources, the HEADER content and FOOTER content will be lost once
v2.5, or later, of MHonArc processes an archive containing these resources.

The HEADER and FOOTER resources have been deprecated for a long time since
they only applied to the main index; the thread index has no equivalent.
The IDXPGBEGIN or LISTBEGIN resources can be used to achieve the same
effect of HEADER. The IDXPGEND or LISTEND can be used to achieve the same
effect of FOOTER.

UPGRADING FROM v2.4.x OR EARLIER: MIMEFILTERS API Change

The API for data filters registered via MIMEFILTERS is not capability with
filters written for v2.4.x and earlier. See CHANGES and the documentation
for the MIMEFILTERS resource for the API.

If you use custom style filters written for v2.4.x, or earlier, you will
need to update them for them to work properly under v2.5, and later.

UPGRADING FROM v2.1.x OR EARLIER: Database Format Change

If you have archives created with v2.1.x, or earlier, the format of
mime-related resources is not compatible with v2.2, and later, versions.
MHonArc will reset the mime-related resources CHARSETCONVERTERS and 
MIMEFILTERS to their default values. MIMEARGS will also be reset to the
default value unless you are upgrading to v2.5.8, or later, where the
MIMEARGS settings will be preserved.

To avoid the resetting of the mime-related resource if you are using
customized settings, you will need to re-specify your settings the next
time you update an archive. If you always specify your resource settings
each time you invoke MHonArc, then your settings should to still take
effect.

You can also use the mha-dbedit program to apply your settings directly
without processing the archive.

DOWNGRADING TO OLDER VERSIONS

Downgrading to an earlier version of MHonArc can be dangerous, especially
if downgrading to an older version that used different storage formats in
archive database files from the current version in use. If an older version
of MHonArc is used to process an archive last updated by a new version,
archive data can get lost and/or unexpected output can occur.

Changes in archive format are not common, so downgrading can be okay
depending on the versions involved. The key versions to watch out for are
the ones noted in this section where database format changes have occured.
The following lists release numbers where a format change occured:

  * 2.0.0
  * 2.2.0
  * 2.5.0

For example, if an archive was last updated with v2.5.0, processing the
archive with a previous release will cause problems.

A possible method for successfully downgrading to a release with
differences in the database format, is to try to reconstruct the database
file using the mha-dbrecover utility contained in the MHonArc version the
archive is being downgraded to.

Of course, the safest way to downgrade is to recreate an archive from the
original raw mail data. It is good practice to preserve the raw mail data
in some form for cases like these and for general archive recovering
situations due to file corruption or other system failures.

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General Notes

  * For v2.5, the default text/html filter (mhtxthtml.pl) will now convert
    auto-loaded URL attributes to 'javascript:void(0);' for some HTML
    elements -- IMG, BODY, IFRAME, FRAME, OBJECT, SCRIPT, INPUT -- except
    for cid: URLs. This behavior can be disabled if the 'allownoncidurls'
    filter argument is specified.
   
    The new behavior is to prevent malicious URLs that verify mail
    addresses for spam purposes, secretly set cookies, or gather some
    statistical data automatically with the use of elements that cause
    browsers to automatically fetch data.
   
  * ISO-8859 character set data processing now defaults to using the
    MHonArc::CharEnt module in v2.5. The old iso8859.pl library is still
    provided for compatibility with older archives. To update archives to
    use the new settings, you can run the following command,
   
        mha-dbedit -rcfile examples/def-mime.mrc \
               -outdir /path/to/archive 
   
    where "examples/def-mime.mrc" represents the default MIME processing
    resources for MHonArc provided within the MHonArc distribution.
   
    NOTE  v2.5.4, and later, generated archives will automatically inherit 
          new CHARSETCONVERTERS if the built-in defaults are being used.   
          However, if you have defined CHARSETCONVERTERS for your archives,
          you will need to explicitly update your archives if you want them
          applied to your archives.                                        
   
  * The value of the TSLICE resource is used to determine the number of
    messages to update, before and after by thread, of each new message
    added. To insure that messages within a thread slice are updated when a
    new message is added, make sure the before and after ranges specified
    for TSLICE is equal to maximum before and the maximum after range
    arguments specifed in the uses of the $TSLICE$ resource variable. For
    example, if you have $TSLICE(0;4)$ and $TSLICE(3;3)$ in message layout
    resources, you should set TSLICE to 3:4.
   
    If you only use $TSLICE$ once, it is best to set options for thread
    slice formatting via the TSLICE resource so you will not have anything
    to worry about.
   
  * If updgrading from v2.4.x, or earlier, reference and follow-up
    information of a message is now stored in a different format in the
    database (and internally). MHonArc will auto-update older archives to
    the new format, so no action should be required on your part.
   
  * If upgrading from v2.1.x, or earlier, any custom filters you have
    developed may need to modified. If your filter accessed some main
    variables, your filter will not operate properly. All variables that
    used to be in package "main" are no longer. The major variables are now
    in package "mhonarc". For example, $::OUTDIR is now $mhonarc::OUTDIR.
    See the MIMEFILTERS resource page for more information.
   
  * See the warnings in the documentation for the HTMLEXT and MSGPREFIX
    resources before using them.
   
  * Occasionally, a new release of MHonArc may contain new MIME filters.
    See the CHANGES file to check if any new filters have been added.
   
    If you confirm that new filters have been added, and you want to apply
    them to your archives, you use the mha-dbedit program using the 
    def-mime.mrc in the examples directory.
   
    NOTE  v2.5.4, and later, generated archives will automatically inherit 
          new MIMEFILTERS if the built-in defaults are being used. However,
          if you have defined MIMEFILTERS for your archives, you will need 
          to explicitly update your archives if you want them applied to   
          your archives.                                                   
   
    Example usage of mha-dbedit:
   
        mha-dbedit -rcfile examples/def-mime.mrc \
               -outdir /path/to/archive 
   
    Change the -rcfile and -outdir pathnames to reflect where you are
    running mhonarc and where your archive is located, respectively.
   
    Note, if your archives are using custom settings of MIMEFILTERS, 
    MIMEARGS, and/or CHARSETCONVERTERS resources, you will need to create a
    variant version of def-mime.mrc (included in the examples directory) to
    include your settings and use the variant version when updating your
    archives.
   
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$Date: 2002/06/27 05:00:01 $
[monicon] MHonArc
Copyright  1997-2001, Earl Hood, mhonarc@mhonarc.org

