define_commit_slab(indegree_slab, int);
 
 /* record author-date for each commit object */
-define_commit_slab(author_date_slab, unsigned long);
+define_commit_slab(author_date_slab, timestamp_t);
 
 static void record_author_date(struct author_date_slab *author_date,
                               struct commit *commit)
        int i;
        uint32_t last_gen = GENERATION_NUMBER_INFINITY;
 
+       if (!min_generation)
+               queue.compare = compare_commits_by_commit_date;
+
        one->object.flags |= PARENT1;
        if (!n) {
                commit_list_append(one, &result);
                struct commit_list *parents;
                int flags;
 
-               if (commit->generation > last_gen)
+               if (min_generation && commit->generation > last_gen)
                        BUG("bad generation skip %8x > %8x at %s",
                            commit->generation, last_gen,
                            oid_to_hex(&commit->object.oid));