Merge branch 'ak/commit-graph-to-slab'

A few fields in "struct commit" that do not have to always be
present have been moved to commit slabs.

* ak/commit-graph-to-slab:
  commit-graph: minimize commit_graph_data_slab access
  commit: move members graph_pos, generation to a slab
  commit-graph: introduce commit_graph_data_slab
  object: drop parsed_object_pool->commit_count

refs.c

@@ -341,7 +341,7 @@ enum peel_status peel_object(const struct object_id *name, struct object_id *oid
 
 	if (o->type == OBJ_NONE) {
 		int type = oid_object_info(the_repository, name, NULL);
-		if (type < 0 || !object_as_type(the_repository, o, type, 0))
+		if (type < 0 || !object_as_type(o, type, 0))
 			return PEEL_INVALID;
 	}