Re: [PATCH v4 2/2] pack-objects: Teach it to use reachability bitmap index when generating non-stdout pack too

@@ -2527,7 +2528,7 @@ static int get_object_list_from_bitmap(struct rev_info *revs)
 	if (prepare_bitmap_walk(revs) < 0)
 		return -1;
 
-	if (pack_options_allow_reuse() &&
+	if (pack_options_allow_reuse() && pack_to_stdout &&
 	    !reuse_partial_packfile_from_bitmap(

@@ -2812,7 +2813,23 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	if (!rev_list_all || !rev_list_reflog || !rev_list_index)
 		unpack_unreachable_expiration = 0;
 
-	if (!use_internal_rev_list || !pack_to_stdout || is_repository_shallow())
+	/*
+	 * "soft" reasons not to use bitmaps - for on-disk repack by default we want
+	 *
+	 * - to produce good pack (with bitmap index not-yet-packed objects are
+	 *   packed in suboptimal order).
+	 *
+	 * - to use more robust pack-generation codepath (avoiding possible
+	 *   bugs in bitmap code and possible bitmap index corruption).
+	 */
+	if (!pack_to_stdout)
+		use_bitmap_index_default = 0;
+
+	if (use_bitmap_index < 0)
+		use_bitmap_index = use_bitmap_index_default;
+
+	/* "hard" reasons not to use bitmaps; these just won't work at all */
+	if (!use_internal_rev_list || (!pack_to_stdout && write_bitmap_index) || is_repository_shallow())
 		use_bitmap_index = 0;

+test_expect_success 'pack-objects to file can use bitmap' '
+	# make sure we still have 1 bitmap index from previous tests
+	ls .git/objects/pack/ | grep bitmap >output &&
+	test_line_count = 1 output &&
+	# verify equivalent packs are generated with/without using bitmap index
+	packasha1=$(git pack-objects --no-use-bitmap-index --all packa </dev/null) &&
+	packbsha1=$(git pack-objects --use-bitmap-index --all packb </dev/null) &&
+	git verify-pack -v packa-$packasha1.pack >packa.verify &&
+	git verify-pack -v packb-$packbsha1.pack >packb.verify &&
+	grep -o "^$_x40" packa.verify |sort >packa.objects &&
+	grep -o "^$_x40" packb.verify |sort >packb.objects &&
+	test_cmp packa.objects packb.objects
+'