receive-pack: quarantine objects until pre-receive accepts

When a client pushes objects to us, index-pack checks the
objects themselves and then installs them into place. If we
then reject the push due to a pre-receive hook, we cannot
just delete the packfile; other processes may be depending
on it. We have to do a normal reachability check at this
point via `git gc`.

But such objects may hang around for weeks due to the
gc.pruneExpire grace period. And worse, during that time
they may be exploded from the pack into inefficient loose
objects.

Instead, this patch teaches receive-pack to put the new
objects into a "quarantine" temporary directory. We make
these objects available to the connectivity check and to the
pre-receive hook, and then install them into place only if
it is successful (and otherwise remove them as tempfiles).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/t/t5547-push-quarantine.sh b/t/t5547-push-quarantine.sh
new file mode 100755
index 0000000000..1e5d32d068
--- /dev/null
+++ b/t/t5547-push-quarantine.sh
@@ -0,0 +1,36 @@
+#!/bin/sh
+
+test_description='check quarantine of objects during push'
+. ./test-lib.sh
+
+test_expect_success 'create picky dest repo' '
+	git init --bare dest.git &&
+	write_script dest.git/hooks/pre-receive <<-\EOF
+	while read old new ref; do
+		test "$(git log -1 --format=%s $new)" = reject && exit 1
+	done
+	exit 0
+	EOF
+'
+
+test_expect_success 'accepted objects work' '
+	test_commit ok &&
+	git push dest.git HEAD &&
+	commit=$(git rev-parse HEAD) &&
+	git --git-dir=dest.git cat-file commit $commit
+'
+
+test_expect_success 'rejected objects are not installed' '
+	test_commit reject &&
+	commit=$(git rev-parse HEAD) &&
+	test_must_fail git push dest.git reject &&
+	test_must_fail git --git-dir=dest.git cat-file commit $commit
+'
+
+test_expect_success 'rejected objects are removed' '
+	echo "incoming-*" >expect &&
+	(cd dest.git/objects && echo incoming-*) >actual &&
+	test_cmp expect actual
+'
+
+test_done