[PATCH 0/8] Updated git-gc --auto series.

An updated series of "git-gc --auto", on top of 'next',
consisting of 8 patches, will follow this message.

Differences from the previous round are:

 - Earlier if you have too many unreachable loose objects,
   automated gc would have tried to "repack -d -l" which would
   not improve the situation at all every time it was run.  It
   now at least warns upon such a situation;

 - pack-objects learned --keep-unreachable option which helps
   "repack -a -d" not to lose packed but unreachable objects
   while repacking existing packs into a new pack;

 - repack learned -A option which is similar to -a but gives
   --keep-unreachable to underlying pack-objects;

 - "git-gc --auto" runs "git-repack -A -d -l" when there are too
   many packs in the repository;

 - These changes are documented ;-)