The Debian FTP-masters recently changed the way gzipped meta files are compressed in order to make them more efficient to update using the rsync option. This was done by adding the --rsyncable option when calling gzip.

Consequence was however that when debmirror compressed Packages, Sources and Contents files after updating them by applying diffs, the md5sum of the gzipped file created by debmirror no longer matched the md5sum listed in the Release file (because debmirror did not use --rsyncable).

Result was that debmirror would also download the full gzipped Packages, Sources and Contents files from the parent mirror, something the diffs are meant to avoid. Not nice.

Anyway, this has been fixed in debmirror 2.4 which now by default also uses --rsyncable when gzipping the updated meta files.

I've also uploaded a fixed version for Lenny (20070123lenny1), which should soon be available from proposed-updates and will be included in the next stable point release.

For archives that also provide diffs (most archives don't have them) but do not have rsyncable gzipped files, the default options used when calling gzip can be overruled using the new option --gzip-options (only in version 2.4).

Tip: if you are using the rsync method to download files, using --diff=none may well be more efficient now that the archive has rsyncable gzipped meta files.

Version 2.4 also has a few other improvements and fixes. If you're currently using version 2.3.x an update to the new version is probably a good idea.