Merge branch 'ds/reachable-first-parent-fix'

Correct performance regression in commit ancestry computation when
generation numbers are involved.

* ds/reachable-first-parent-fix:
  commit-reach: fix first-parent heuristic

Author: gitster

commit-reach.c

@@ -593,8 +593,10 @@ int can_all_from_reach_with_flag(struct object_array *from,
 		while (stack) {
 			struct commit_list *parent;
 
-			if (stack->item->object.flags & with_flag) {
+			if (stack->item->object.flags & (with_flag | RESULT)) {
 				pop_commit(&stack);
+				if (stack)
+					stack->item->object.flags |= RESULT;
 				continue;
 			}