gc: clean garbage .bitmap files from pack dir

Similar to cleaning up excess .idx files, clean any garbage .bitmap
files that are not otherwise associated with any .idx/.pack files.

Signed-off-by: Doug Kelly <[email protected]>
Suggested-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: vangdfang

builtin/gc.c

@@ -58,8 +58,41 @@ static void clean_pack_garbage(void)
 
 static void report_pack_garbage(unsigned seen_bits, const char *path)
 {
-	if (seen_bits == PACKDIR_FILE_IDX)
+	/* We know these are useless without the matching .pack */
+	if (ends_with(path, ".bitmap") || ends_with(path, ".idx")) {
 		string_list_append(&pack_garbage, path);
+		return;
+	}
+
+	/*
+	 * A pack without other files cannot be used, but should be saved,
+	 * as this is a recoverable situation (we may even see it racily
+	 * as new packs come into existence).
+	 */
+	if (ends_with(path, ".pack"))
+		return;
+
+	/*
+	 * A .keep file is useless without the matching pack, but it
+	 * _could_ contain information generated by the user. Let's keep it.
+	 * In the future, we may expand this to look for obvious leftover
+	 * receive-pack locks and drop them.
+	 */
+	if (ends_with(path, ".keep"))
+		return;
+
+	/*
+	 * A totally unrelated garbage file should be kept, to err
+	 * on the conservative side.
+	 */
+	if (seen_bits & PACKDIR_FILE_GARBAGE)
+		return;
+
+	/*
+	 * We have a file type that the garbage-reporting functions
+	 * know about but we don't. This function needs updating.
+	 */
+	die("BUG: report_pack_garbage confused");
 }
 
 static void git_config_date_string(const char *key, const char **output)

t/t5304-prune.sh

@@ -257,7 +257,7 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_failure 'clean pack garbage with gc' '
+test_expect_success 'clean pack garbage with gc' '
 	test_when_finished "rm -f .git/objects/pack/fake*" &&
 	test_when_finished "rm -f .git/objects/pack/foo*" &&
 	: >.git/objects/pack/foo.keep &&