midx.c: avoid cruft packs with non-zero `repack --batch-size`

Apply similar treatment with respect to cruft packs as in a few commits
ago to `repack` with a non-zero `--batch-size`.

Since the case of a non-zero `--batch-size` is handled separately (in
`fill_included_packs_batch()` instead of `fill_included_packs_all()`), a
separate fix must be applied for this case.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/midx.c b/midx.c
index 273704c..3a8dcfe 100644
--- a/midx.c
+++ b/midx.c
@@ -1946,6 +1946,8 @@ static int fill_included_packs_batch(struct repository *r,
 			continue;
 		if (!pack_kept_objects && p->pack_keep)
 			continue;
+		if (p->is_cruft)
+			continue;
 		if (open_pack_index(p) || !p->num_objects)
 			continue;