gc: do not explode objects which will be immediately pruned

When we pack everything into one big pack with "git repack
-Ad", any unreferenced objects in to-be-deleted packs are
exploded into loose objects, with the intent that they will
be examined and possibly cleaned up by the next run of "git
prune".

Since the exploded objects will receive the mtime of the
pack from which they come, if the source pack is old, those
loose objects will end up pruned immediately. In that case,
it is much more efficient to skip the exploding step
entirely for these objects.

This patch teaches pack-objects to receive the expiration
information and avoid writing these objects out. It also
teaches "git gc" to pass the value of gc.pruneexpire to
repack (which in turn learns to pass it along to
pack-objects) so that this optimization happens
automatically during "git gc" and "git gc --auto".

Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/git-repack.sh b/git-repack.sh
index 624feec26..757933174 100755
--- a/git-repack.sh
+++ b/git-repack.sh
@@ -15,6 +15,7 @@ F               pass --no-reuse-object to git-pack-objects
 n               do not run git-update-server-info
 q,quiet         be quiet
 l               pass --local to git-pack-objects
+unpack-unreachable=  with -A, do not loosen objects older than this
  Packing constraints
 window=         size of the window used for delta compression
 window-memory=  same as the above, but limit memory size instead of entries count
@@ -33,6 +34,8 @@ do
 	-a)	all_into_one=t ;;
 	-A)	all_into_one=t
 		unpack_unreachable=--unpack-unreachable ;;
+	--unpack-unreachable)
+		unpack_unreachable="--unpack-unreachable=$2"; shift ;;
 	-d)	remove_redundant=t ;;
 	-q)	GIT_QUIET=t ;;
 	-f)	no_reuse=--no-reuse-delta ;;
@@ -76,7 +79,12 @@ case ",$all_into_one," in
 		if test -n "$existing" -a -n "$unpack_unreachable" -a \
 			-n "$remove_redundant"
 		then
-			args="$args $unpack_unreachable"
+			# This may have arbitrary user arguments, so we
+			# have to protect it against whitespace splitting
+			# when it gets run as "pack-objects $args" later.
+			# Fortunately, we know it's an approxidate, so we
+			# can just use dots instead.
+			args="$args $(echo "$unpack_unreachable" | tr ' ' .)"
 		fi
 	fi
 	;;