midx: teach bsearch_midx() about incremental MIDXs

Now that the special cases callers of `bsearch_midx()` have been dealt
with, teach `bsearch_midx()` to handle incremental MIDX chains.

The incremental MIDX-aware version of `bsearch_midx()` works by
repeatedly searching for a given OID in each layer along the
`->base_midx` pointer, stopping either when an exact match is found, or
the end of the chain is reached.

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

midx.c

@@ -344,7 +344,10 @@ int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
 int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m,
 		 uint32_t *result)
 {
-		return bsearch_one_midx(oid, m, result);
+	for (; m; m = m->base_midx)
+		if (bsearch_one_midx(oid, m, result))
+			return 1;
+	return 0;
 }
 
 struct object_id *nth_midxed_object_oid(struct object_id *oid,