git-rev-list: make sure the output is sorted by recency

We didn't sort the refs by date, so if you had multiple refs, the end
result would not be properly sorted.

rev-list.c

@@ -482,7 +482,7 @@ int main(int argc, char **argv)
 		commit = get_commit_reference(arg, flags);
 		if (!commit)
 			continue;
-		commit_list_insert(commit, &list);
+		insert_by_date(&list, commit);
 	}
 
 	if (!merge_order) {