midx: remove now-unused linked list of multi-pack indices

In the preceding commits we have migrated all users of the linked list
of multi-pack indices to instead use those stored in the object database
sources. Remove those now-unused pointers.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

midx.c

@@ -726,7 +726,6 @@ int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id)
 int prepare_multi_pack_index_one(struct odb_source *source, int local)
 {
 	struct repository *r = source->odb->repo;
-	struct multi_pack_index *m;
 
 	prepare_repo_settings(r);
 	if (!r->settings.core_multi_pack_index)
@@ -735,21 +734,9 @@ int prepare_multi_pack_index_one(struct odb_source *source, int local)
 	if (source->midx)
 		return 1;
 
-	m = load_multi_pack_index(r, source->path, local);
-	if (m) {
-		struct multi_pack_index *mp = r->objects->multi_pack_index;
-		if (mp) {
-			m->next = mp->next;
-			mp->next = m;
-		} else {
-			r->objects->multi_pack_index = m;
-		}
-		source->midx = m;
+	source->midx = load_multi_pack_index(r, source->path, local);
 
-		return 1;
-	}
-
-	return 0;
+	return !!source->midx;
 }
 
 int midx_checksum_valid(struct multi_pack_index *m)
@@ -842,7 +829,6 @@ void clear_midx_file(struct repository *r)
 				close_midx(source->midx);
 			source->midx = NULL;
 		}
-		r->objects->multi_pack_index = NULL;
 	}
 
 	if (remove_path(midx.buf))

midx.h

@@ -35,8 +35,6 @@ struct odb_source;
 	"GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL"
 
 struct multi_pack_index {
-	struct multi_pack_index *next;
-
 	const unsigned char *data;
 	size_t data_len;
 

odb.h

@@ -123,13 +123,6 @@ struct object_database {
 	struct commit_graph *commit_graph;
 	unsigned commit_graph_attempted : 1; /* if loading has been attempted */
 
-	/*
-	 * private data
-	 *
-	 * should only be accessed directly by packfile.c and midx.c
-	 */
-	struct multi_pack_index *multi_pack_index;
-
 	/*
 	 * private data
 	 *

packfile.c

@@ -375,7 +375,6 @@ void close_object_store(struct object_database *o)
 			close_midx(source->midx);
 		source->midx = NULL;
 	}
-	o->multi_pack_index = NULL;
 
 	close_commit_graph(o);
 }