Merge branch 'bc/repack'

Merge branch 'bc/repack'

* bc/repack:
  Documentation/git-repack.txt: document new -A behaviour
  let pack-objects do the writing of unreachable objects as loose objects
  add a force_object_loose() function
  builtin-gc.c: deprecate --prune, it now really has no effect
  git-gc: always use -A when manually repacking
  repack: modify behavior of -A option to leave unreferenced objects unpacked

Conflicts:

	builtin-pack-objects.c