Merge branch 'ps/repack-avoid-noop-midx-rewrite' into tb/midx-write-corrupt-checksum-fix

* ps/repack-avoid-noop-midx-rewrite:
  midx-write: skip rewriting MIDX with `--stdin-packs` unless needed
  midx-write: extract function to test whether MIDX needs updating
  midx: fix `BUG()` when getting preferred pack without a reverse index

2 files changed, 99 insertions, 0 deletions

diff --git a/t/t5319-multi-pack-index.sh b/t/t5319-multi-pack-index.sh
index 93f319a4b2..794f8b5ab4 100755
--- a/t/t5319-multi-pack-index.sh
+++ b/t/t5319-multi-pack-index.sh
@@ -350,9 +350,73 @@ test_expect_success 'preferred pack from existing MIDX without bitmaps' '
 		# the new MIDX
 		git multi-pack-index write --preferred-pack=pack-$pack.pack
 	)
+'
+
+test_expect_success 'preferred pack cannot be determined without bitmap' '
+	test_when_finished "rm -fr preferred-can-be-queried" &&
+	git init preferred-can-be-queried &&
+	(
+		cd preferred-can-be-queried &&
+		test_commit initial &&
+		git repack -Adl --write-midx --no-write-bitmap-index &&
+		test_must_fail test-tool read-midx --preferred-pack .git/objects 2>err &&
+		test_grep "could not determine MIDX preferred pack" err &&
+		git repack -Adl --write-midx --write-bitmap-index &&
+		test-tool read-midx --preferred-pack .git/objects
+	)
+'
+
+test_midx_is_retained () {
+	test-tool chmtime =0 .git/objects/pack/multi-pack-index &&
+	ls -l .git/objects/pack/multi-pack-index >expect &&
+	git multi-pack-index write "$@" &&
+	ls -l .git/objects/pack/multi-pack-index >actual &&
+	test_cmp expect actual
+}
+
+test_midx_is_rewritten () {
+	test-tool chmtime =0 .git/objects/pack/multi-pack-index &&
+	ls -l .git/objects/pack/multi-pack-index >expect &&
+	git multi-pack-index write "$@" &&
+	ls -l .git/objects/pack/multi-pack-index >actual &&
+	! test_cmp expect actual
+}
+
+test_expect_success 'up-to-date multi-pack-index is retained' '
+	test_when_finished "rm -fr midx-up-to-date" &&
+	git init midx-up-to-date &&
+	(
+		cd midx-up-to-date &&
+
+		# Write the initial pack that contains the most objects.
+		test_commit first &&
+		test_commit second &&
+		git repack -Ad --write-midx &&
+		test_midx_is_retained &&
+
+		# Writing a new bitmap index should cause us to regenerate the MIDX.
+		test_midx_is_rewritten --bitmap &&
+		test_midx_is_retained --bitmap &&
 
+		# Ensure that writing a new packfile causes us to rewrite the index.
+		test_commit incremental &&
+		git repack -d &&
+		test_midx_is_rewritten &&
+		test_midx_is_retained &&
+
+		for pack in .git/objects/pack/*.idx
+		do
+			basename "$pack" || exit 1
+		done >stdin &&
+		test_line_count = 2 stdin &&
+		test_midx_is_retained --stdin-packs <stdin &&
+		head -n1 stdin >stdin.trimmed &&
+		test_midx_is_rewritten --stdin-packs <stdin.trimmed
+	)
 '
 
+test_done
+
 test_expect_success 'verify multi-pack-index success' '
 	git multi-pack-index verify --object-dir=$objdir
 '
diff --git a/t/t7703-repack-geometric.sh b/t/t7703-repack-geometric.sh
index 9fc1626fbf..98806cdb6f 100755
--- a/t/t7703-repack-geometric.sh
+++ b/t/t7703-repack-geometric.sh
@@ -287,6 +287,41 @@ test_expect_success '--geometric with pack.packSizeLimit' '
 	)
 '
 
+test_expect_success '--geometric --write-midx retains up-to-date MIDX without bitmap index' '
+	test_when_finished "rm -fr repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit initial &&
+
+		test_path_is_missing .git/objects/pack/multi-pack-index &&
+		git repack --geometric=2 --write-midx --no-write-bitmap-index &&
+		test_path_is_file .git/objects/pack/multi-pack-index &&
+		test-tool chmtime =0 .git/objects/pack/multi-pack-index &&
+
+		ls -l .git/objects/pack/ >expect &&
+		git repack --geometric=2 --write-midx --no-write-bitmap-index &&
+		ls -l .git/objects/pack/ >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '--geometric --write-midx retains up-to-date MIDX with bitmap index' '
+	test_when_finished "rm -fr repo" &&
+	git init repo &&
+	test_commit -C repo initial &&
+
+	test_path_is_missing repo/.git/objects/pack/multi-pack-index &&
+	git -C repo repack --geometric=2 --write-midx --write-bitmap-index &&
+	test_path_is_file repo/.git/objects/pack/multi-pack-index &&
+	test-tool chmtime =0 repo/.git/objects/pack/multi-pack-index &&
+
+	ls -l repo/.git/objects/pack/ >expect &&
+	git -C repo repack --geometric=2 --write-midx --write-bitmap-index &&
+	ls -l repo/.git/objects/pack/ >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success '--geometric --write-midx with packfiles in main and alternate ODB' '
 	test_when_finished "rm -fr shared member" &&