remove .keep pack lock files when done with refs update

This makes both git-fetch and git-push (fetch-pack and receive-pack)
safe against a possible race with aparallel git-repack -a -d that could
prune the new pack while it is not yet referenced, and remove the .keep
file after refs have been updated.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-fetch.sh

@@ -51,7 +51,7 @@ do
 		verbose=Yes
 		;;
 	-k|--k|--ke|--kee|--keep)
-		keep=--keep
+		keep='-k -k'
 		;;
 	--reflog-action=*)
 		rloga=`expr "z$1" : 'z-[^=]*=\(.*\)'`
@@ -368,6 +368,7 @@ fetch_main () {
       ;; # we are already done.
   *)
     ( : subshell because we muck with IFS
+      pack_lockfile=
       IFS=" 	$LF"
       (
 	  git-fetch-pack --thin $exec $keep "$remote" $rref || echo failed "$remote"
@@ -378,6 +379,12 @@ fetch_main () {
 	  failed)
 		  echo >&2 "Fetch failure: $remote"
 		  exit 1 ;;
+	  # special line coming from index-pack with the pack name
+	  pack)
+		  continue ;;
+	  keep)
+		  pack_lockfile="$GIT_OBJECT_DIRECTORY/pack/pack-$remote_name.keep"
+		  continue ;;
 	  esac
 	  found=
 	  single_force=
@@ -408,6 +415,7 @@ fetch_main () {
 	  append_fetch_head "$sha1" "$remote" \
 		  "$remote_name" "$remote_nick" "$local_name" "$not_for_merge"
       done
+      if [ "$pack_lockfile" ]; then rm -f "$pack_lockfile"; fi
     ) || exit ;;
   esac