if (!sb.len)
                        string_list_append(&subjects,
-                                          sha1_to_hex(commit->object.sha1));
+                                          oid_to_hex(&commit->object.oid));
                else
                        string_list_append(&subjects, strbuf_detach(&sb, NULL));
        }
                if (!parent)
                        continue;
                commit_list_insert(parent, &parents);
-               add_merge_parent(result, get_object_hash(*obj), get_object_hash(parent->object));
+               add_merge_parent(result, obj->oid.hash, parent->object.oid.hash);
        }
        head_commit = lookup_commit(head);
        if (head_commit)
        while (parents) {
                struct commit *cmit = pop_commit(&parents);
                for (i = 0; i < result->nr; i++)
-                       if (!hashcmp(result->item[i].commit, get_object_hash(cmit->object)))
+                       if (!hashcmp(result->item[i].commit, cmit->object.oid.hash))
                                result->item[i].used = 1;
        }