Merge branch 'jc/autogc'

* jc/autogc:
  git-gc --auto: run "repack -A -d -l" as necessary.
  git-gc --auto: restructure the way "repack" command line is built.
  git-gc --auto: protect ourselves from accumulated cruft
  git-gc --auto: add documentation.
  git-gc --auto: move threshold check to need_to_gc() function.
  repack -A -d: use --keep-unreachable when repacking
  pack-objects --keep-unreachable
  Export matches_pack_name() and fix its return value
  Invoke "git gc --auto" from commit, merge, am and rebase.
  Implement git gc --auto

git-merge.sh

@@ -82,6 +82,7 @@ finish () {
 			;;
 		*)
 			git update-ref -m "$rlogm" HEAD "$1" "$head" || exit 1
+			git gc --auto
 			;;
 		esac
 		;;