Re: [PATCH v2 01/24] pack-bitmap.c: harden 'test_bitmap_walk()' to check type bitmaps

On Mon, Jun 21, 2021 at 06:24:59PM -0400, Taylor Blau wrote:

The special `--test-bitmap` mode of `git rev-list` is used to compare
the result of an object traversal with a bitmap to check its integrity.
This mode does not, however, assert that the types of reachable objects
are stored correctly.

Harden this mode by teaching it to also check that each time an object's
bit is marked, the corresponding bit should be set in exactly one of the
type bitmaps (whose type matches the object's true type).

Yep, makes sense, and the patch looks good.

+{
+	enum object_type bitmap_type = OBJ_NONE;
[...]
+
+	if (!bitmap_type)
+		die("object %s not found in type bitmaps",
+		    oid_to_hex(&obj->oid));

I think the suggestion to do:

  if (bitmap_type == OBJ_NONE)

is reasonable here, as it assumes less about the enum. I do think
OBJ_BAD and OBJ_NONE were chosen with these kind of numeric comparisons
in mind, but there is no reason to rely on them in places we don't need
to.

-Peff