debian/patches/fsck-parse-loose-object-paths-directly.diff

From c0be469507a2a1381f881f1c2c1c70ad00499b00 Mon Sep 17 00:00:00 2001
From: Jeff King <peff@peff.net>
Date: Fri, 13 Jan 2017 12:59:44 -0500
Subject: fsck: parse loose object paths directly

commit c68b489e56431cf27f7719913ab09ddc62f95912 upstream.

When we iterate over the list of loose objects to check, we
get the actual path of each object. But we then throw it
away and pass just the sha1 to fsck_sha1(), which will do a
fresh lookup. Usually it would find the same object, but it
may not if an object exists both as a loose and a packed
object. We may end up checking the packed object twice, and
never look at the loose one.

In practice this isn't too terrible, because if fsck doesn't
complain, it means you have at least one good copy. But
since the point of fsck is to look for corruption, we should
be thorough.

The new read_loose_object() interface can help us get the
data from disk, and then we replace parse_object() with
parse_object_buffer(). As a bonus, our error messages now
mention the path to a corrupted object, which should make it
easier to track down errors when they do happen.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
 builtin/fsck.c  | 46 +++++++++++++++++++++++++++++++++-------------
 t/t1450-fsck.sh | 16 ++++++++++++++++
 2 files changed, 49 insertions(+), 13 deletions(-)

diff --git a/builtin/fsck.c b/builtin/fsck.c
index f01b81eebf..4b91ee95e6 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c
@@ -362,18 +362,6 @@ static int fsck_obj(struct object *obj)
 	return 0;
 }
 
-static int fsck_sha1(const unsigned char *sha1)
-{
-	struct object *obj = parse_object(sha1);
-	if (!obj) {
-		errors_found |= ERROR_OBJECT;
-		return error("%s: object corrupt or missing",
-			     sha1_to_hex(sha1));
-	}
-	obj->flags |= HAS_OBJ;
-	return fsck_obj(obj);
-}
-
 static int fsck_obj_buffer(const unsigned char *sha1, enum object_type type,
 			   unsigned long size, void *buffer, int *eaten)
 {
@@ -488,9 +476,41 @@ static void get_default_heads(void)
 	}
 }
 
+static struct object *parse_loose_object(const unsigned char *sha1,
+					 const char *path)
+{
+	struct object *obj;
+	void *contents;
+	enum object_type type;
+	unsigned long size;
+	int eaten;
+
+	if (read_loose_object(path, sha1, &type, &size, &contents) < 0)
+		return NULL;
+
+	if (!contents && type != OBJ_BLOB)
+		die("BUG: read_loose_object streamed a non-blob");
+
+	obj = parse_object_buffer(sha1, type, size, contents, &eaten);
+
+	if (!eaten)
+		free(contents);
+	return obj;
+}
+
 static int fsck_loose(const unsigned char *sha1, const char *path, void *data)
 {
-	if (fsck_sha1(sha1))
+	struct object *obj = parse_loose_object(sha1, path);
+
+	if (!obj) {
+		errors_found |= ERROR_OBJECT;
+		error("%s: object corrupt or missing: %s",
+		      sha1_to_hex(sha1), path);
+		return 0; /* keep checking other objects */
+	}
+
+	obj->flags = HAS_OBJ;
+	if (fsck_obj(obj))
 		errors_found |= ERROR_OBJECT;
 	return 0;
 }
diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh
index ee7d4736db..a817d8fdd9 100755
--- a/t/t1450-fsck.sh
+++ b/t/t1450-fsck.sh
@@ -557,4 +557,20 @@ test_expect_success 'fsck --name-objects' '
 	)
 '
 
+test_expect_success 'fsck finds problems in duplicate loose objects' '
+	rm -rf broken-duplicate &&
+	git init broken-duplicate &&
+	(
+		cd broken-duplicate &&
+		test_commit duplicate &&
+		# no "-d" here, so we end up with duplicates
+		git repack &&
+		# now corrupt the loose copy
+		file=$(sha1_file "$(git rev-parse HEAD)") &&
+		rm "$file" &&
+		echo broken >"$file" &&
+		test_must_fail git fsck
+	)
+'
+
 test_done
-- 
2.17.0.921.gf22659ad46