packfile: stop using linked MIDX list in get_all_packs()

Refactor `get_all_packs()` so that we stop using the linked list of
multi-pack indices. Note that there is no need to explicitly prepare
alternates, and neither do we have to use `get_multi_pack_index()`,
because `prepare_packed_git()` already takes care of populating all data
structures for us.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

packfile.c

@@ -1086,12 +1086,13 @@ struct multi_pack_index *get_multi_pack_index(struct odb_source *source)
 
 struct packed_git *get_all_packs(struct repository *r)
 {
-	struct multi_pack_index *m;
-
 	prepare_packed_git(r);
-	for (m = r->objects->multi_pack_index; m; m = m->next) {
-		uint32_t i;
-		for (i = 0; i < m->num_packs + m->num_packs_in_base; i++)
+
+	for (struct odb_source *source = r->objects->sources; source; source = source->next) {
+		struct multi_pack_index *m = source->midx;
+		if (!m)
+			continue;
+		for (uint32_t i = 0; i < m->num_packs + m->num_packs_in_base; i++)
 			prepare_midx_pack(r, m, i);
 	}