Adding upstream version 1:2.43.0.upstream/1%2.43.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1168 insertions, 0 deletions

diff --git a/commit-reach.c b/commit-reach.c
new file mode 100644
index 0000000..a868a57
--- /dev/null
+++ b/commit-reach.c
@@ -0,0 +1,1168 @@
+#include "git-compat-util.h"
+#include "commit.h"
+#include "commit-graph.h"
+#include "decorate.h"
+#include "hex.h"
+#include "prio-queue.h"
+#include "tree.h"
+#include "ref-filter.h"
+#include "revision.h"
+#include "tag.h"
+#include "commit-reach.h"
+#include "ewah/ewok.h"
+
+/* Remember to update object flag allocation in object.h */
+#define PARENT1		(1u<<16)
+#define PARENT2		(1u<<17)
+#define STALE		(1u<<18)
+#define RESULT		(1u<<19)
+
+static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);
+
+static int compare_commits_by_gen(const void *_a, const void *_b)
+{
+	const struct commit *a = *(const struct commit * const *)_a;
+	const struct commit *b = *(const struct commit * const *)_b;
+
+	timestamp_t generation_a = commit_graph_generation(a);
+	timestamp_t generation_b = commit_graph_generation(b);
+
+	if (generation_a < generation_b)
+		return -1;
+	if (generation_a > generation_b)
+		return 1;
+	if (a->date < b->date)
+		return -1;
+	if (a->date > b->date)
+		return 1;
+	return 0;
+}
+
+static int queue_has_nonstale(struct prio_queue *queue)
+{
+	int i;
+	for (i = 0; i < queue->nr; i++) {
+		struct commit *commit = queue->array[i].data;
+		if (!(commit->object.flags & STALE))
+			return 1;
+	}
+	return 0;
+}
+
+/* all input commits in one and twos[] must have been parsed! */
+static struct commit_list *paint_down_to_common(struct repository *r,
+						struct commit *one, int n,
+						struct commit **twos,
+						timestamp_t min_generation)
+{
+	struct prio_queue queue = { compare_commits_by_gen_then_commit_date };
+	struct commit_list *result = NULL;
+	int i;
+	timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
+
+	if (!min_generation && !corrected_commit_dates_enabled(r))
+		queue.compare = compare_commits_by_commit_date;
+
+	one->object.flags |= PARENT1;
+	if (!n) {
+		commit_list_append(one, &result);
+		return result;
+	}
+	prio_queue_put(&queue, one);
+
+	for (i = 0; i < n; i++) {
+		twos[i]->object.flags |= PARENT2;
+		prio_queue_put(&queue, twos[i]);
+	}
+
+	while (queue_has_nonstale(&queue)) {
+		struct commit *commit = prio_queue_get(&queue);
+		struct commit_list *parents;
+		int flags;
+		timestamp_t generation = commit_graph_generation(commit);
+
+		if (min_generation && generation > last_gen)
+			BUG("bad generation skip %"PRItime" > %"PRItime" at %s",
+			    generation, last_gen,
+			    oid_to_hex(&commit->object.oid));
+		last_gen = generation;
+
+		if (generation < min_generation)
+			break;
+
+		flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
+		if (flags == (PARENT1 | PARENT2)) {
+			if (!(commit->object.flags & RESULT)) {
+				commit->object.flags |= RESULT;
+				commit_list_insert_by_date(commit, &result);
+			}
+			/* Mark parents of a found merge stale */
+			flags |= STALE;
+		}
+		parents = commit->parents;
+		while (parents) {
+			struct commit *p = parents->item;
+			parents = parents->next;
+			if ((p->object.flags & flags) == flags)
+				continue;
+			if (repo_parse_commit(r, p))
+				return NULL;
+			p->object.flags |= flags;
+			prio_queue_put(&queue, p);
+		}
+	}
+
+	clear_prio_queue(&queue);
+	return result;
+}
+
+static struct commit_list *merge_bases_many(struct repository *r,
+					    struct commit *one, int n,
+					    struct commit **twos)
+{
+	struct commit_list *list = NULL;
+	struct commit_list *result = NULL;
+	int i;
+
+	for (i = 0; i < n; i++) {
+		if (one == twos[i])
+			/*
+			 * We do not mark this even with RESULT so we do not
+			 * have to clean it up.
+			 */
+			return commit_list_insert(one, &result);
+	}
+
+	if (repo_parse_commit(r, one))
+		return NULL;
+	for (i = 0; i < n; i++) {
+		if (repo_parse_commit(r, twos[i]))
+			return NULL;
+	}
+
+	list = paint_down_to_common(r, one, n, twos, 0);
+
+	while (list) {
+		struct commit *commit = pop_commit(&list);
+		if (!(commit->object.flags & STALE))
+			commit_list_insert_by_date(commit, &result);
+	}
+	return result;
+}
+
+struct commit_list *get_octopus_merge_bases(struct commit_list *in)
+{
+	struct commit_list *i, *j, *k, *ret = NULL;
+
+	if (!in)
+		return ret;
+
+	commit_list_insert(in->item, &ret);
+
+	for (i = in->next; i; i = i->next) {
+		struct commit_list *new_commits = NULL, *end = NULL;
+
+		for (j = ret; j; j = j->next) {
+			struct commit_list *bases;
+			bases = repo_get_merge_bases(the_repository, i->item,
+						     j->item);
+			if (!new_commits)
+				new_commits = bases;
+			else
+				end->next = bases;
+			for (k = bases; k; k = k->next)
+				end = k;
+		}
+		free_commit_list(ret);
+		ret = new_commits;
+	}
+	return ret;
+}
+
+static int remove_redundant_no_gen(struct repository *r,
+				   struct commit **array, int cnt)
+{
+	struct commit **work;
+	unsigned char *redundant;
+	int *filled_index;
+	int i, j, filled;
+
+	CALLOC_ARRAY(work, cnt);
+	redundant = xcalloc(cnt, 1);
+	ALLOC_ARRAY(filled_index, cnt - 1);
+
+	for (i = 0; i < cnt; i++)
+		repo_parse_commit(r, array[i]);
+	for (i = 0; i < cnt; i++) {
+		struct commit_list *common;
+		timestamp_t min_generation = commit_graph_generation(array[i]);
+
+		if (redundant[i])
+			continue;
+		for (j = filled = 0; j < cnt; j++) {
+			timestamp_t curr_generation;
+			if (i == j || redundant[j])
+				continue;
+			filled_index[filled] = j;
+			work[filled++] = array[j];
+
+			curr_generation = commit_graph_generation(array[j]);
+			if (curr_generation < min_generation)
+				min_generation = curr_generation;
+		}
+		common = paint_down_to_common(r, array[i], filled,
+					      work, min_generation);
+		if (array[i]->object.flags & PARENT2)
+			redundant[i] = 1;
+		for (j = 0; j < filled; j++)
+			if (work[j]->object.flags & PARENT1)
+				redundant[filled_index[j]] = 1;
+		clear_commit_marks(array[i], all_flags);
+		clear_commit_marks_many(filled, work, all_flags);
+		free_commit_list(common);
+	}
+
+	/* Now collect the result */
+	COPY_ARRAY(work, array, cnt);
+	for (i = filled = 0; i < cnt; i++)
+		if (!redundant[i])
+			array[filled++] = work[i];
+	free(work);
+	free(redundant);
+	free(filled_index);
+	return filled;
+}
+
+static int remove_redundant_with_gen(struct repository *r,
+				     struct commit **array, int cnt)
+{
+	int i, count_non_stale = 0, count_still_independent = cnt;
+	timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
+	struct commit **walk_start, **sorted;
+	size_t walk_start_nr = 0, walk_start_alloc = cnt;
+	int min_gen_pos = 0;
+
+	/*
+	 * Sort the input by generation number, ascending. This allows
+	 * us to increase the "min_generation" limit when we discover
+	 * the commit with lowest generation is STALE. The index
+	 * min_gen_pos points to the current position within 'array'
+	 * that is not yet known to be STALE.
+	 */
+	DUP_ARRAY(sorted, array, cnt);
+	QSORT(sorted, cnt, compare_commits_by_gen);
+	min_generation = commit_graph_generation(sorted[0]);
+
+	ALLOC_ARRAY(walk_start, walk_start_alloc);
+
+	/* Mark all parents of the input as STALE */
+	for (i = 0; i < cnt; i++) {
+		struct commit_list *parents;
+
+		repo_parse_commit(r, array[i]);
+		array[i]->object.flags |= RESULT;
+		parents = array[i]->parents;
+
+		while (parents) {
+			repo_parse_commit(r, parents->item);
+			if (!(parents->item->object.flags & STALE)) {
+				parents->item->object.flags |= STALE;
+				ALLOC_GROW(walk_start, walk_start_nr + 1, walk_start_alloc);
+				walk_start[walk_start_nr++] = parents->item;
+			}
+			parents = parents->next;
+		}
+	}
+
+	QSORT(walk_start, walk_start_nr, compare_commits_by_gen);
+
+	/* remove STALE bit for now to allow walking through parents */
+	for (i = 0; i < walk_start_nr; i++)
+		walk_start[i]->object.flags &= ~STALE;
+
+	/*
+	 * Start walking from the highest generation. Hopefully, it will
+	 * find all other items during the first-parent walk, and we can
+	 * terminate early. Otherwise, we will do the same amount of work
+	 * as before.
+	 */
+	for (i = walk_start_nr - 1; i >= 0 && count_still_independent > 1; i--) {
+		/* push the STALE bits up to min generation */
+		struct commit_list *stack = NULL;
+
+		commit_list_insert(walk_start[i], &stack);
+		walk_start[i]->object.flags |= STALE;
+
+		while (stack) {
+			struct commit_list *parents;
+			struct commit *c = stack->item;
+
+			repo_parse_commit(r, c);
+
+			if (c->object.flags & RESULT) {
+				c->object.flags &= ~RESULT;
+				if (--count_still_independent <= 1)
+					break;
+				if (oideq(&c->object.oid, &sorted[min_gen_pos]->object.oid)) {
+					while (min_gen_pos < cnt - 1 &&
+					       (sorted[min_gen_pos]->object.flags & STALE))
+						min_gen_pos++;
+					min_generation = commit_graph_generation(sorted[min_gen_pos]);
+				}
+			}
+
+			if (commit_graph_generation(c) < min_generation) {
+				pop_commit(&stack);
+				continue;
+			}
+
+			parents = c->parents;
+			while (parents) {
+				if (!(parents->item->object.flags & STALE)) {
+					parents->item->object.flags |= STALE;
+					commit_list_insert(parents->item, &stack);
+					break;
+				}
+				parents = parents->next;
+			}
+
+			/* pop if all parents have been visited already */
+			if (!parents)
+				pop_commit(&stack);
+		}
+		free_commit_list(stack);
+	}
+	free(sorted);
+
+	/* clear result */
+	for (i = 0; i < cnt; i++)
+		array[i]->object.flags &= ~RESULT;
+
+	/* rearrange array */
+	for (i = count_non_stale = 0; i < cnt; i++) {
+		if (!(array[i]->object.flags & STALE))
+			array[count_non_stale++] = array[i];
+	}
+
+	/* clear marks */
+	clear_commit_marks_many(walk_start_nr, walk_start, STALE);
+	free(walk_start);
+
+	return count_non_stale;
+}
+
+static int remove_redundant(struct repository *r, struct commit **array, int cnt)
+{
+	/*
+	 * Some commit in the array may be an ancestor of
+	 * another commit.  Move the independent commits to the
+	 * beginning of 'array' and return their number. Callers
+	 * should not rely upon the contents of 'array' after
+	 * that number.
+	 */
+	if (generation_numbers_enabled(r)) {
+		int i;
+
+		/*
+		 * If we have a single commit with finite generation
+		 * number, then the _with_gen algorithm is preferred.
+		 */
+		for (i = 0; i < cnt; i++) {
+			if (commit_graph_generation(array[i]) < GENERATION_NUMBER_INFINITY)
+				return remove_redundant_with_gen(r, array, cnt);
+		}
+	}
+
+	return remove_redundant_no_gen(r, array, cnt);
+}
+
+static struct commit_list *get_merge_bases_many_0(struct repository *r,
+						  struct commit *one,
+						  int n,
+						  struct commit **twos,
+						  int cleanup)
+{
+	struct commit_list *list;
+	struct commit **rslt;
+	struct commit_list *result;
+	int cnt, i;
+
+	result = merge_bases_many(r, one, n, twos);
+	for (i = 0; i < n; i++) {
+		if (one == twos[i])
+			return result;
+	}
+	if (!result || !result->next) {
+		if (cleanup) {
+			clear_commit_marks(one, all_flags);
+			clear_commit_marks_many(n, twos, all_flags);
+		}
+		return result;
+	}
+
+	/* There are more than one */
+	cnt = commit_list_count(result);
+	CALLOC_ARRAY(rslt, cnt);
+	for (list = result, i = 0; list; list = list->next)
+		rslt[i++] = list->item;
+	free_commit_list(result);
+
+	clear_commit_marks(one, all_flags);
+	clear_commit_marks_many(n, twos, all_flags);
+
+	cnt = remove_redundant(r, rslt, cnt);
+	result = NULL;
+	for (i = 0; i < cnt; i++)
+		commit_list_insert_by_date(rslt[i], &result);
+	free(rslt);
+	return result;
+}
+
+struct commit_list *repo_get_merge_bases_many(struct repository *r,
+					      struct commit *one,
+					      int n,
+					      struct commit **twos)
+{
+	return get_merge_bases_many_0(r, one, n, twos, 1);
+}
+
+struct commit_list *repo_get_merge_bases_many_dirty(struct repository *r,
+						    struct commit *one,
+						    int n,
+						    struct commit **twos)
+{
+	return get_merge_bases_many_0(r, one, n, twos, 0);
+}
+
+struct commit_list *repo_get_merge_bases(struct repository *r,
+					 struct commit *one,
+					 struct commit *two)
+{
+	return get_merge_bases_many_0(r, one, 1, &two, 1);
+}
+
+/*
+ * Is "commit" a descendant of one of the elements on the "with_commit" list?
+ */
+int repo_is_descendant_of(struct repository *r,
+			  struct commit *commit,
+			  struct commit_list *with_commit)
+{
+	if (!with_commit)
+		return 1;
+
+	if (generation_numbers_enabled(r)) {
+		struct commit_list *from_list = NULL;
+		int result;
+		commit_list_insert(commit, &from_list);
+		result = can_all_from_reach(from_list, with_commit, 0);
+		free_commit_list(from_list);
+		return result;
+	} else {
+		while (with_commit) {
+			struct commit *other;
+
+			other = with_commit->item;
+			with_commit = with_commit->next;
+			if (repo_in_merge_bases_many(r, other, 1, &commit))
+				return 1;
+		}
+		return 0;
+	}
+}
+
+/*
+ * Is "commit" an ancestor of one of the "references"?
+ */
+int repo_in_merge_bases_many(struct repository *r, struct commit *commit,
+			     int nr_reference, struct commit **reference)
+{
+	struct commit_list *bases;
+	int ret = 0, i;
+	timestamp_t generation, max_generation = GENERATION_NUMBER_ZERO;
+
+	if (repo_parse_commit(r, commit))
+		return ret;
+	for (i = 0; i < nr_reference; i++) {
+		if (repo_parse_commit(r, reference[i]))
+			return ret;
+
+		generation = commit_graph_generation(reference[i]);
+		if (generation > max_generation)
+			max_generation = generation;
+	}
+
+	generation = commit_graph_generation(commit);
+	if (generation > max_generation)
+		return ret;
+
+	bases = paint_down_to_common(r, commit,
+				     nr_reference, reference,
+				     generation);
+	if (commit->object.flags & PARENT2)
+		ret = 1;
+	clear_commit_marks(commit, all_flags);
+	clear_commit_marks_many(nr_reference, reference, all_flags);
+	free_commit_list(bases);
+	return ret;
+}
+
+/*
+ * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
+ */
+int repo_in_merge_bases(struct repository *r,
+			struct commit *commit,
+			struct commit *reference)
+{
+	int res;
+	struct commit_list *list = NULL;
+	struct commit_list **next = &list;
+
+	next = commit_list_append(commit, next);
+	res = repo_is_descendant_of(r, reference, list);
+	free_commit_list(list);
+
+	return res;
+}
+
+struct commit_list *reduce_heads(struct commit_list *heads)
+{
+	struct commit_list *p;
+	struct commit_list *result = NULL, **tail = &result;
+	struct commit **array;
+	int num_head, i;
+
+	if (!heads)
+		return NULL;
+
+	/* Uniquify */
+	for (p = heads; p; p = p->next)
+		p->item->object.flags &= ~STALE;
+	for (p = heads, num_head = 0; p; p = p->next) {
+		if (p->item->object.flags & STALE)
+			continue;
+		p->item->object.flags |= STALE;
+		num_head++;
+	}
+	CALLOC_ARRAY(array, num_head);
+	for (p = heads, i = 0; p; p = p->next) {
+		if (p->item->object.flags & STALE) {
+			array[i++] = p->item;
+			p->item->object.flags &= ~STALE;
+		}
+	}
+	num_head = remove_redundant(the_repository, array, num_head);
+	for (i = 0; i < num_head; i++)
+		tail = &commit_list_insert(array[i], tail)->next;
+	free(array);
+	return result;
+}
+
+void reduce_heads_replace(struct commit_list **heads)
+{
+	struct commit_list *result = reduce_heads(*heads);
+	free_commit_list(*heads);
+	*heads = result;
+}
+
+int ref_newer(const struct object_id *new_oid, const struct object_id *old_oid)
+{
+	struct object *o;
+	struct commit *old_commit, *new_commit;
+	struct commit_list *old_commit_list = NULL;
+	int ret;
+
+	/*
+	 * Both new_commit and old_commit must be commit-ish and new_commit is descendant of
+	 * old_commit.  Otherwise we require --force.
+	 */
+	o = deref_tag(the_repository, parse_object(the_repository, old_oid),
+		      NULL, 0);
+	if (!o || o->type != OBJ_COMMIT)
+		return 0;
+	old_commit = (struct commit *) o;
+
+	o = deref_tag(the_repository, parse_object(the_repository, new_oid),
+		      NULL, 0);
+	if (!o || o->type != OBJ_COMMIT)
+		return 0;
+	new_commit = (struct commit *) o;
+
+	if (repo_parse_commit(the_repository, new_commit) < 0)
+		return 0;
+
+	commit_list_insert(old_commit, &old_commit_list);
+	ret = repo_is_descendant_of(the_repository,
+				    new_commit, old_commit_list);
+	free_commit_list(old_commit_list);
+	return ret;
+}
+
+/*
+ * Mimicking the real stack, this stack lives on the heap, avoiding stack
+ * overflows.
+ *
+ * At each recursion step, the stack items points to the commits whose
+ * ancestors are to be inspected.
+ */
+struct contains_stack {
+	int nr, alloc;
+	struct contains_stack_entry {
+		struct commit *commit;
+		struct commit_list *parents;
+	} *contains_stack;
+};
+
+static int in_commit_list(const struct commit_list *want, struct commit *c)
+{
+	for (; want; want = want->next)
+		if (oideq(&want->item->object.oid, &c->object.oid))
+			return 1;
+	return 0;
+}
+
+/*
+ * Test whether the candidate is contained in the list.
+ * Do not recurse to find out, though, but return -1 if inconclusive.
+ */
+static enum contains_result contains_test(struct commit *candidate,
+					  const struct commit_list *want,
+					  struct contains_cache *cache,
+					  timestamp_t cutoff)
+{
+	enum contains_result *cached = contains_cache_at(cache, candidate);
+
+	/* If we already have the answer cached, return that. */
+	if (*cached)
+		return *cached;
+
+	/* or are we it? */
+	if (in_commit_list(want, candidate)) {
+		*cached = CONTAINS_YES;
+		return CONTAINS_YES;
+	}
+
+	/* Otherwise, we don't know; prepare to recurse */
+	parse_commit_or_die(candidate);
+
+	if (commit_graph_generation(candidate) < cutoff)
+		return CONTAINS_NO;
+
+	return CONTAINS_UNKNOWN;
+}
+
+static void push_to_contains_stack(struct commit *candidate, struct contains_stack *contains_stack)
+{
+	ALLOC_GROW(contains_stack->contains_stack, contains_stack->nr + 1, contains_stack->alloc);
+	contains_stack->contains_stack[contains_stack->nr].commit = candidate;
+	contains_stack->contains_stack[contains_stack->nr++].parents = candidate->parents;
+}
+
+static enum contains_result contains_tag_algo(struct commit *candidate,
+					      const struct commit_list *want,
+					      struct contains_cache *cache)
+{
+	struct contains_stack contains_stack = { 0, 0, NULL };
+	enum contains_result result;
+	timestamp_t cutoff = GENERATION_NUMBER_INFINITY;
+	const struct commit_list *p;
+
+	for (p = want; p; p = p->next) {
+		timestamp_t generation;
+		struct commit *c = p->item;
+		load_commit_graph_info(the_repository, c);
+		generation = commit_graph_generation(c);
+		if (generation < cutoff)
+			cutoff = generation;
+	}
+
+	result = contains_test(candidate, want, cache, cutoff);
+	if (result != CONTAINS_UNKNOWN)
+		return result;
+
+	push_to_contains_stack(candidate, &contains_stack);
+	while (contains_stack.nr) {
+		struct contains_stack_entry *entry = &contains_stack.contains_stack[contains_stack.nr - 1];
+		struct commit *commit = entry->commit;
+		struct commit_list *parents = entry->parents;
+
+		if (!parents) {
+			*contains_cache_at(cache, commit) = CONTAINS_NO;
+			contains_stack.nr--;
+		}
+		/*
+		 * If we just popped the stack, parents->item has been marked,
+		 * therefore contains_test will return a meaningful yes/no.
+		 */
+		else switch (contains_test(parents->item, want, cache, cutoff)) {
+		case CONTAINS_YES:
+			*contains_cache_at(cache, commit) = CONTAINS_YES;
+			contains_stack.nr--;
+			break;
+		case CONTAINS_NO:
+			entry->parents = parents->next;
+			break;
+		case CONTAINS_UNKNOWN:
+			push_to_contains_stack(parents->item, &contains_stack);
+			break;
+		}
+	}
+	free(contains_stack.contains_stack);
+	return contains_test(candidate, want, cache, cutoff);
+}
+
+int commit_contains(struct ref_filter *filter, struct commit *commit,
+		    struct commit_list *list, struct contains_cache *cache)
+{
+	if (filter->with_commit_tag_algo)
+		return contains_tag_algo(commit, list, cache) == CONTAINS_YES;
+	return repo_is_descendant_of(the_repository, commit, list);
+}
+
+int can_all_from_reach_with_flag(struct object_array *from,
+				 unsigned int with_flag,
+				 unsigned int assign_flag,
+				 time_t min_commit_date,
+				 timestamp_t min_generation)
+{
+	struct commit **list = NULL;
+	int i;
+	int nr_commits;
+	int result = 1;
+
+	ALLOC_ARRAY(list, from->nr);
+	nr_commits = 0;
+	for (i = 0; i < from->nr; i++) {
+		struct object *from_one = from->objects[i].item;
+
+		if (!from_one || from_one->flags & assign_flag)
+			continue;
+
+		from_one = deref_tag(the_repository, from_one,
+				     "a from object", 0);
+		if (!from_one || from_one->type != OBJ_COMMIT) {
+			/*
+			 * no way to tell if this is reachable by
+			 * looking at the ancestry chain alone, so
+			 * leave a note to ourselves not to worry about
+			 * this object anymore.
+			 */
+			from->objects[i].item->flags |= assign_flag;
+			continue;
+		}
+
+		list[nr_commits] = (struct commit *)from_one;
+		if (repo_parse_commit(the_repository, list[nr_commits]) ||
+		    commit_graph_generation(list[nr_commits]) < min_generation) {
+			result = 0;
+			goto cleanup;
+		}
+
+		nr_commits++;
+	}
+
+	QSORT(list, nr_commits, compare_commits_by_gen);
+
+	for (i = 0; i < nr_commits; i++) {
+		/* DFS from list[i] */
+		struct commit_list *stack = NULL;
+
+		list[i]->object.flags |= assign_flag;
+		commit_list_insert(list[i], &stack);
+
+		while (stack) {
+			struct commit_list *parent;
+
+			if (stack->item->object.flags & (with_flag | RESULT)) {
+				pop_commit(&stack);
+				if (stack)
+					stack->item->object.flags |= RESULT;
+				continue;
+			}
+
+			for (parent = stack->item->parents; parent; parent = parent->next) {
+				if (parent->item->object.flags & (with_flag | RESULT))
+					stack->item->object.flags |= RESULT;
+
+				if (!(parent->item->object.flags & assign_flag)) {
+					parent->item->object.flags |= assign_flag;
+
+					if (repo_parse_commit(the_repository, parent->item) ||
+					    parent->item->date < min_commit_date ||
+					    commit_graph_generation(parent->item) < min_generation)
+						continue;
+
+					commit_list_insert(parent->item, &stack);
+					break;
+				}
+			}
+
+			if (!parent)
+				pop_commit(&stack);
+		}
+
+		if (!(list[i]->object.flags & (with_flag | RESULT))) {
+			result = 0;
+			goto cleanup;
+		}
+	}
+
+cleanup:
+	clear_commit_marks_many(nr_commits, list, RESULT | assign_flag);
+	free(list);
+
+	for (i = 0; i < from->nr; i++) {
+		struct object *from_one = from->objects[i].item;
+
+		if (from_one)
+			from_one->flags &= ~assign_flag;
+	}
+
+	return result;
+}
+
+int can_all_from_reach(struct commit_list *from, struct commit_list *to,
+		       int cutoff_by_min_date)
+{
+	struct object_array from_objs = OBJECT_ARRAY_INIT;
+	time_t min_commit_date = cutoff_by_min_date ? from->item->date : 0;
+	struct commit_list *from_iter = from, *to_iter = to;
+	int result;
+	timestamp_t min_generation = GENERATION_NUMBER_INFINITY;
+
+	while (from_iter) {
+		add_object_array(&from_iter->item->object, NULL, &from_objs);
+
+		if (!repo_parse_commit(the_repository, from_iter->item)) {
+			timestamp_t generation;
+			if (from_iter->item->date < min_commit_date)
+				min_commit_date = from_iter->item->date;
+
+			generation = commit_graph_generation(from_iter->item);
+			if (generation < min_generation)
+				min_generation = generation;
+		}
+
+		from_iter = from_iter->next;
+	}
+
+	while (to_iter) {
+		if (!repo_parse_commit(the_repository, to_iter->item)) {
+			timestamp_t generation;
+			if (to_iter->item->date < min_commit_date)
+				min_commit_date = to_iter->item->date;
+
+			generation = commit_graph_generation(to_iter->item);
+			if (generation < min_generation)
+				min_generation = generation;
+		}
+
+		to_iter->item->object.flags |= PARENT2;
+
+		to_iter = to_iter->next;
+	}
+
+	result = can_all_from_reach_with_flag(&from_objs, PARENT2, PARENT1,
+					      min_commit_date, min_generation);
+
+	while (from) {
+		clear_commit_marks(from->item, PARENT1);
+		from = from->next;
+	}
+
+	while (to) {
+		clear_commit_marks(to->item, PARENT2);
+		to = to->next;
+	}
+
+	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;
+	timestamp_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++) {
+		timestamp_t generation;
+		struct commit *c = *item;
+
+		repo_parse_commit(the_repository, c);
+		generation = commit_graph_generation(c);
+		if (generation < min_generation)
+			min_generation = 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;
+			repo_parse_commit(the_repository, 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;
+
+			repo_parse_commit(the_repository, p);
+
+			if (commit_graph_generation(p) < min_generation)
+				continue;
+
+			if (p->object.flags & PARENT2)
+				continue;
+
+			p->object.flags |= PARENT2;
+			prio_queue_put(&queue, p);
+		}
+	}
+
+	clear_prio_queue(&queue);
+
+	clear_commit_marks_many(nr_to, to, PARENT1);
+	clear_commit_marks_many(nr_from, from, PARENT2);
+
+	return found_commits;
+}
+
+define_commit_slab(bit_arrays, struct bitmap *);
+static struct bit_arrays bit_arrays;
+
+static void insert_no_dup(struct prio_queue *queue, struct commit *c)
+{
+	if (c->object.flags & PARENT2)
+		return;
+	prio_queue_put(queue, c);
+	c->object.flags |= PARENT2;
+}
+
+static struct bitmap *get_bit_array(struct commit *c, int width)
+{
+	struct bitmap **bitmap = bit_arrays_at(&bit_arrays, c);
+	if (!*bitmap)
+		*bitmap = bitmap_word_alloc(width);
+	return *bitmap;
+}
+
+static void free_bit_array(struct commit *c)
+{
+	struct bitmap **bitmap = bit_arrays_at(&bit_arrays, c);
+	if (!*bitmap)
+		return;
+	bitmap_free(*bitmap);
+	*bitmap = NULL;
+}
+
+void ahead_behind(struct repository *r,
+		  struct commit **commits, size_t commits_nr,
+		  struct ahead_behind_count *counts, size_t counts_nr)
+{
+	struct prio_queue queue = { .compare = compare_commits_by_gen_then_commit_date };
+	size_t width = DIV_ROUND_UP(commits_nr, BITS_IN_EWORD);
+
+	if (!commits_nr || !counts_nr)
+		return;
+
+	for (size_t i = 0; i < counts_nr; i++) {
+		counts[i].ahead = 0;
+		counts[i].behind = 0;
+	}
+
+	ensure_generations_valid(r, commits, commits_nr);
+
+	init_bit_arrays(&bit_arrays);
+
+	for (size_t i = 0; i < commits_nr; i++) {
+		struct commit *c = commits[i];
+		struct bitmap *bitmap = get_bit_array(c, width);
+
+		bitmap_set(bitmap, i);
+		insert_no_dup(&queue, c);
+	}
+
+	while (queue_has_nonstale(&queue)) {
+		struct commit *c = prio_queue_get(&queue);
+		struct commit_list *p;
+		struct bitmap *bitmap_c = get_bit_array(c, width);
+
+		for (size_t i = 0; i < counts_nr; i++) {
+			int reach_from_tip = !!bitmap_get(bitmap_c, counts[i].tip_index);
+			int reach_from_base = !!bitmap_get(bitmap_c, counts[i].base_index);
+
+			if (reach_from_tip ^ reach_from_base) {
+				if (reach_from_base)
+					counts[i].behind++;
+				else
+					counts[i].ahead++;
+			}
+		}
+
+		for (p = c->parents; p; p = p->next) {
+			struct bitmap *bitmap_p;
+
+			repo_parse_commit(r, p->item);
+
+			bitmap_p = get_bit_array(p->item, width);
+			bitmap_or(bitmap_p, bitmap_c);
+
+			/*
+			 * If this parent is reachable from every starting
+			 * commit, then none of its ancestors can contribute
+			 * to the ahead/behind count. Mark it as STALE, so
+			 * we can stop the walk when every commit in the
+			 * queue is STALE.
+			 */
+			if (bitmap_popcount(bitmap_p) == commits_nr)
+				p->item->object.flags |= STALE;
+
+			insert_no_dup(&queue, p->item);
+		}
+
+		free_bit_array(c);
+	}
+
+	/* STALE is used here, PARENT2 is used by insert_no_dup(). */
+	repo_clear_commit_marks(r, PARENT2 | STALE);
+	clear_bit_arrays(&bit_arrays);
+	clear_prio_queue(&queue);
+}
+
+struct commit_and_index {
+	struct commit *commit;
+	unsigned int index;
+	timestamp_t generation;
+};
+
+static int compare_commit_and_index_by_generation(const void *va, const void *vb)
+{
+	const struct commit_and_index *a = (const struct commit_and_index *)va;
+	const struct commit_and_index *b = (const struct commit_and_index *)vb;
+
+	if (a->generation > b->generation)
+		return 1;
+	if (a->generation < b->generation)
+		return -1;
+	return 0;
+}
+
+void tips_reachable_from_bases(struct repository *r,
+			       struct commit_list *bases,
+			       struct commit **tips, size_t tips_nr,
+			       int mark)
+{
+	struct commit_and_index *commits;
+	size_t min_generation_index = 0;
+	timestamp_t min_generation;
+	struct commit_list *stack = NULL;
+
+	if (!bases || !tips || !tips_nr)
+		return;
+
+	/*
+	 * Do a depth-first search starting at 'bases' to search for the
+	 * tips. Stop at the lowest (un-found) generation number. When
+	 * finding the lowest commit, increase the minimum generation
+	 * number to the next lowest (un-found) generation number.
+	 */
+
+	CALLOC_ARRAY(commits, tips_nr);
+
+	for (size_t i = 0; i < tips_nr; i++) {
+		commits[i].commit = tips[i];
+		commits[i].index = i;
+		commits[i].generation = commit_graph_generation(tips[i]);
+	}
+
+	/* Sort with generation number ascending. */
+	QSORT(commits, tips_nr, compare_commit_and_index_by_generation);
+	min_generation = commits[0].generation;
+
+	while (bases) {
+		repo_parse_commit(r, bases->item);
+		commit_list_insert(bases->item, &stack);
+		bases = bases->next;
+	}
+
+	while (stack) {
+		int explored_all_parents = 1;
+		struct commit_list *p;
+		struct commit *c = stack->item;
+		timestamp_t c_gen = commit_graph_generation(c);
+
+		/* Does it match any of our tips? */
+		for (size_t j = min_generation_index; j < tips_nr; j++) {
+			if (c_gen < commits[j].generation)
+				break;
+
+			if (commits[j].commit == c) {
+				tips[commits[j].index]->object.flags |= mark;
+
+				if (j == min_generation_index) {
+					unsigned int k = j + 1;
+					while (k < tips_nr &&
+					       (tips[commits[k].index]->object.flags & mark))
+						k++;
+
+					/* Terminate early if all found. */
+					if (k >= tips_nr)
+						goto done;
+
+					min_generation_index = k;
+					min_generation = commits[k].generation;
+				}
+			}
+		}
+
+		for (p = c->parents; p; p = p->next) {
+			repo_parse_commit(r, p->item);
+
+			/* Have we already explored this parent? */
+			if (p->item->object.flags & SEEN)
+				continue;
+
+			/* Is it below the current minimum generation? */
+			if (commit_graph_generation(p->item) < min_generation)
+				continue;
+
+			/* Ok, we will explore from here on. */
+			p->item->object.flags |= SEEN;
+			explored_all_parents = 0;
+			commit_list_insert(p->item, &stack);
+			break;
+		}
+
+		if (explored_all_parents)
+			pop_commit(&stack);
+	}
+
+done:
+	free(commits);
+	repo_clear_commit_marks(r, SEEN);
+}