recognize loose local objects during repack

This was developed on top of the previous repack/pack-objects series.


Junio wrote:

Presumably you meant "exclude objects accessible through alternates,
either in packs or in loose form"?  If so then I think it is a good thing
to have.

This patch set looks like what is necessary to exclude loose objects accessible
through alternates from packing.

I think the useful kinds are only these five:

 - scoop loose objects that exist in local repository into a new pack,
   without touching existing packs at all; exclude anything available in
   any existing pack or in alternate repository (either loose or packed);

  repack -l

 - pack everything that is needed by the local ref, except the ones that
   are borrowed from alternate repositories (either loose or packed), into
   a single new pack.  There are two variants of this: eject what is
   currently packed but unnecessary into loose format when existing local
   packs are replaced with the new pack, or lose them (i.e. -A).

  repack -a -l
  repack -A -l

 - fatten local repository by packing everything that is needed by the
   local ref into a single new pack, including things that are currently
   borrowed from alternates.  There are two variants of this: eject what
   is currently packed but unnecessary into loose format when existing
   local packs are replaced with the new pack, or lose them (i.e. -A).

  repack -a
  repack -A

-brandon