midx: teach midx_contains_pack() about incremental MIDXs

Now that the `midx_contains_pack()` versus `midx_locate_pack()` debacle
has been cleaned up, teach the former about how to operate in an
incremental MIDX-aware world in a similar fashion as in previous
commits.

Instead of using either of the two `midx_for_object()` or
`midx_for_pack()` helpers, this function is split into two: one that
determines whether a pack is contained in a single MIDX, and another
which calls the former in a loop over all MIDXs.

This approach does not require that we change any of the implementation
in what is now `midx_contains_pack_1()` as it still operates over a
single MIDX.

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

Author: ttaylorr

midx.c

@@ -466,7 +466,8 @@ int cmp_idx_or_pack_name(const char *idx_or_pack_name,
 	return strcmp(idx_or_pack_name, idx_name);
 }
 
-int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
+static int midx_contains_pack_1(struct multi_pack_index *m,
+				const char *idx_or_pack_name)
 {
 	uint32_t first = 0, last = m->num_packs;
 
@@ -489,6 +490,14 @@ int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
 	return 0;
 }
 
+int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
+{
+	for (; m; m = m->base_midx)
+		if (midx_contains_pack_1(m, idx_or_pack_name))
+			return 1;
+	return 0;
+}
+
 int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id)
 {
 	if (m->preferred_pack_idx == -1) {