1 files changed, 74 insertions, 3 deletions

diff --git a/commit-reach.c b/commit-reach.c
index 8715008fef..3ea174788a 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -542,8 +542,8 @@ int commit_contains(struct ref_filter *filter, struct commit *commit,
 
 static int compare_commits_by_gen(const void *_a, const void *_b)
 {
-	const struct commit *a = (const struct commit *)_a;
-	const struct commit *b = (const struct commit *)_b;
+	const struct commit *a = *(const struct commit * const *)_a;
+	const struct commit *b = *(const struct commit * const *)_b;
 
 	if (a->generation < b->generation)
 		return -1;
@@ -606,8 +606,10 @@ 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;
 			}
 
@@ -701,3 +703,72 @@ int can_all_from_reach(struct commit_list *from, struct commit_list *to,
 	object_array_clear(&from_objs);
 	return result;
 }
+
+struct commit_list *get_reachable_subset(struct commit **from, int nr_from,
+					 struct commit **to, int nr_to,
+					 unsigned int reachable_flag)
+{
+	struct commit **item;
+	struct commit *current;
+	struct commit_list *found_commits = NULL;
+	struct commit **to_last = to + nr_to;
+	struct commit **from_last = from + nr_from;
+	uint32_t min_generation = GENERATION_NUMBER_INFINITY;
+	int num_to_find = 0;
+
+	struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
+
+	for (item = to; item < to_last; item++) {
+		struct commit *c = *item;
+
+		parse_commit(c);
+		if (c->generation < min_generation)
+			min_generation = c->generation;
+
+		if (!(c->object.flags & PARENT1)) {
+			c->object.flags |= PARENT1;
+			num_to_find++;
+		}
+	}
+
+	for (item = from; item < from_last; item++) {
+		struct commit *c = *item;
+		if (!(c->object.flags & PARENT2)) {
+			c->object.flags |= PARENT2;
+			parse_commit(c);
+
+			prio_queue_put(&queue, *item);
+		}
+	}
+
+	while (num_to_find && (current = prio_queue_get(&queue)) != NULL) {
+		struct commit_list *parents;
+
+		if (current->object.flags & PARENT1) {
+			current->object.flags &= ~PARENT1;
+			current->object.flags |= reachable_flag;
+			commit_list_insert(current, &found_commits);
+			num_to_find--;
+		}
+
+		for (parents = current->parents; parents; parents = parents->next) {
+			struct commit *p = parents->item;
+
+			parse_commit(p);
+
+			if (p->generation < min_generation)
+				continue;
+
+			if (p->object.flags & PARENT2)
+				continue;
+
+			p->object.flags |= PARENT2;
+			prio_queue_put(&queue, p);
+		}
+	}
+
+	clear_commit_marks_many(nr_to, to, PARENT1);
+	clear_commit_marks_many(nr_from, from, PARENT2);
+
+	return found_commits;
+}