Merge branch 'tb/midx-write-propagate-namehash'

"git multi-pack-index write --bitmap" learns to propagate the
hashcache from original bitmap to resulting bitmap.

* tb/midx-write-propagate-namehash:
  t5326: test propagating hashcache values
  p5326: generate pack bitmaps before writing the MIDX bitmap
  p5326: don't set core.multiPackIndex unnecessarily
  p5326: create missing 'perf-tag' tag
  midx.c: respect 'pack.writeBitmapHashcache' when writing bitmaps
  pack-bitmap.c: propagate namehash values from existing bitmaps
  t/helper/test-bitmap.c: add 'dump-hashes' mode

3 files changed, 51 insertions, 4 deletions

diff --git a/t/helper/test-bitmap.c b/t/helper/test-bitmap.c
index 134a1e9..ff35f59 100644
--- a/t/helper/test-bitmap.c
+++ b/t/helper/test-bitmap.c
@@ -7,6 +7,11 @@ static int bitmap_list_commits(void)
 	return test_bitmap_commits(the_repository);
 }
 
+static int bitmap_dump_hashes(void)
+{
+	return test_bitmap_hashes(the_repository);
+}
+
 int cmd__bitmap(int argc, const char **argv)
 {
 	setup_git_directory();
@@ -16,9 +21,12 @@ int cmd__bitmap(int argc, const char **argv)
 
 	if (!strcmp(argv[1], "list-commits"))
 		return bitmap_list_commits();
+	if (!strcmp(argv[1], "dump-hashes"))
+		return bitmap_dump_hashes();
 
 usage:
-	usage("\ttest-tool bitmap list-commits");
+	usage("\ttest-tool bitmap list-commits\n"
+	      "\ttest-tool bitmap dump-hashes");
 
 	return -1;
 }
diff --git a/t/perf/p5326-multi-pack-bitmaps.sh b/t/perf/p5326-multi-pack-bitmaps.sh
index 5845109..f2fa228 100755
--- a/t/perf/p5326-multi-pack-bitmaps.sh
+++ b/t/perf/p5326-multi-pack-bitmaps.sh
@@ -6,15 +6,24 @@ test_description='Tests performance using midx bitmaps'
 
 test_perf_large_repo
 
-test_expect_success 'enable multi-pack index' '
-	git config core.multiPackIndex true
+# we need to create the tag up front such that it is covered by the repack and
+# thus by generated bitmaps.
+test_expect_success 'create tags' '
+	git tag --message="tag pointing to HEAD" perf-tag HEAD
+'
+
+test_expect_success 'start with bitmapped pack' '
+	git repack -adb
 '
 
 test_perf 'setup multi-pack index' '
-	git repack -ad &&
 	git multi-pack-index write --bitmap
 '
 
+test_expect_success 'drop pack bitmap' '
+	rm -f .git/objects/pack/pack-*.bitmap
+'
+
 test_full_bitmap
 
 test_expect_success 'create partial bitmap state' '
diff --git a/t/t5326-multi-pack-bitmaps.sh b/t/t5326-multi-pack-bitmaps.sh
index 4ad7c2c..ec4aa89 100755
--- a/t/t5326-multi-pack-bitmaps.sh
+++ b/t/t5326-multi-pack-bitmaps.sh
@@ -283,4 +283,34 @@ test_expect_success 'pack.preferBitmapTips' '
 	)
 '
 
+test_expect_success 'hash-cache values are propagated from pack bitmaps' '
+	rm -fr repo &&
+	git init repo &&
+	test_when_finished "rm -fr repo" &&
+	(
+		cd repo &&
+
+		test_commit base &&
+		test_commit base2 &&
+		git repack -adb &&
+
+		test-tool bitmap dump-hashes >pack.raw &&
+		test_file_not_empty pack.raw &&
+		sort pack.raw >pack.hashes &&
+
+		test_commit new &&
+		git repack &&
+		git multi-pack-index write --bitmap &&
+
+		test-tool bitmap dump-hashes >midx.raw &&
+		sort midx.raw >midx.hashes &&
+
+		# ensure that every namehash in the pack bitmap can be found in
+		# the midx bitmap (i.e., that there are no oid-namehash pairs
+		# unique to the pack bitmap).
+		comm -23 pack.hashes midx.hashes >dropped.hashes &&
+		test_must_be_empty dropped.hashes
+	)
+'
+
 test_done