Merge branch 'ds/reachable-topo-order'

The revision walker machinery learned to take advantage of the
commit generation numbers stored in the commit-graph file.

* ds/reachable-topo-order:
  t6012: make rev-list tests more interesting
  revision.c: generation-based topo-order algorithm
  commit/revisions: bookkeeping before refactoring
  revision.c: begin refactoring --topo-order logic
  test-reach: add rev-list tests
  test-reach: add run_three_modes method
  prio-queue: add 'peek' operation

11 files changed, 427 insertions, 39 deletions

diff --git a/commit.c b/commit.c
index d566d7e45c..bee7b7b62e 100644
--- a/commit.c
+++ b/commit.c
@@ -657,11 +657,10 @@ struct commit *pop_commit(struct commit_list **stack)
 /* count number of children that have not been emitted */
 define_commit_slab(indegree_slab, int);
 
-/* record author-date for each commit object */
 define_commit_slab(author_date_slab, timestamp_t);
 
-static void record_author_date(struct author_date_slab *author_date,
-			       struct commit *commit)
+void record_author_date(struct author_date_slab *author_date,
+			struct commit *commit)
 {
 	const char *buffer = get_commit_buffer(commit, NULL);
 	struct ident_split ident;
@@ -686,8 +685,8 @@ fail_exit:
 	unuse_commit_buffer(commit, buffer);
 }
 
-static int compare_commits_by_author_date(const void *a_, const void *b_,
-					  void *cb_data)
+int compare_commits_by_author_date(const void *a_, const void *b_,
+				   void *cb_data)
 {
 	const struct commit *a = a_, *b = b_;
 	struct author_date_slab *author_date = cb_data;
diff --git a/commit.h b/commit.h
index 8f15cfd43b..03ab19508f 100644
--- a/commit.h
+++ b/commit.h
@@ -8,6 +8,7 @@
 #include "gpg-interface.h"
 #include "string-list.h"
 #include "pretty.h"
+#include "commit-slab.h"
 
 #define COMMIT_NOT_FROM_GRAPH 0xFFFFFFFF
 #define GENERATION_NUMBER_INFINITY 0xFFFFFFFF
@@ -333,6 +334,12 @@ extern int remove_signature(struct strbuf *buf);
  */
 extern int check_commit_signature(const struct commit *commit, struct signature_check *sigc);
 
+/* record author-date for each commit object */
+struct author_date_slab;
+void record_author_date(struct author_date_slab *author_date,
+			struct commit *commit);
+
+int compare_commits_by_author_date(const void *a_, const void *b_, void *unused);
 int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused);
 int compare_commits_by_gen_then_commit_date(const void *a_, const void *b_, void *unused);
 
diff --git a/object.h b/object.h
index 0feb90ae61..796792cb32 100644
--- a/object.h
+++ b/object.h
@@ -59,7 +59,7 @@ struct object_array {
 
 /*
  * object flag allocation:
- * revision.h:               0---------10                              2526
+ * revision.h:               0---------10                              25----28
  * fetch-pack.c:             01
  * negotiator/default.c:       2--5
  * walker.c:                 0-2
@@ -78,7 +78,7 @@ struct object_array {
  * builtin/show-branch.c:    0-------------------------------------------26
  * builtin/unpack-objects.c:                                 2021
  */
-#define FLAG_BITS  27
+#define FLAG_BITS  29
 
 /*
  * The object type is stored in 3 bits.
diff --git a/prio-queue.c b/prio-queue.c
index a078451872..d3f488cb05 100644
--- a/prio-queue.c
+++ b/prio-queue.c
@@ -85,3 +85,12 @@ void *prio_queue_get(struct prio_queue *queue)
 	}
 	return result;
 }
+
+void *prio_queue_peek(struct prio_queue *queue)
+{
+	if (!queue->nr)
+		return NULL;
+	if (!queue->compare)
+		return queue->array[queue->nr - 1].data;
+	return queue->array[0].data;
+}
diff --git a/prio-queue.h b/prio-queue.h
index d030ec9dd6..682e51867a 100644
--- a/prio-queue.h
+++ b/prio-queue.h
@@ -46,6 +46,12 @@ extern void prio_queue_put(struct prio_queue *, void *thing);
  */
 extern void *prio_queue_get(struct prio_queue *);
 
+/*
+ * Gain access to the "thing" that would be returned by
+ * prio_queue_get, but do not remove it from the queue.
+ */
+extern void *prio_queue_peek(struct prio_queue *);
+
 extern void clear_prio_queue(struct prio_queue *);
 
 /* Reverse the LIFO elements */
diff --git a/revision.c b/revision.c
index bdd3e7c9f1..13e0519c02 100644
--- a/revision.c
+++ b/revision.c
@@ -25,6 +25,8 @@
 #include "worktree.h"
 #include "argv-array.h"
 #include "commit-reach.h"
+#include "commit-graph.h"
+#include "prio-queue.h"
 
 volatile show_early_output_fn_t show_early_output;
 
@@ -767,8 +769,8 @@ static void commit_list_insert_by_date_cached(struct commit *p, struct commit_li
 		*cache = new_entry;
 }
 
-static int add_parents_to_list(struct rev_info *revs, struct commit *commit,
-		    struct commit_list **list, struct commit_list **cache_ptr)
+static int process_parents(struct rev_info *revs, struct commit *commit,
+			   struct commit_list **list, struct commit_list **cache_ptr)
 {
 	struct commit_list *parent = commit->parents;
 	unsigned left_flag;
@@ -807,7 +809,8 @@ static int add_parents_to_list(struct rev_info *revs, struct commit *commit,
 			if (p->object.flags & SEEN)
 				continue;
 			p->object.flags |= SEEN;
-			commit_list_insert_by_date_cached(p, list, cached_base, cache_ptr);
+			if (list)
+				commit_list_insert_by_date_cached(p, list, cached_base, cache_ptr);
 		}
 		return 0;
 	}
@@ -846,7 +849,8 @@ static int add_parents_to_list(struct rev_info *revs, struct commit *commit,
 		p->object.flags |= left_flag;
 		if (!(p->object.flags & SEEN)) {
 			p->object.flags |= SEEN;
-			commit_list_insert_by_date_cached(p, list, cached_base, cache_ptr);
+			if (list)
+				commit_list_insert_by_date_cached(p, list, cached_base, cache_ptr);
 		}
 		if (revs->first_parent_only)
 			break;
@@ -1090,7 +1094,7 @@ static int limit_list(struct rev_info *revs)
 
 		if (revs->max_age != -1 && (commit->date < revs->max_age))
 			obj->flags |= UNINTERESTING;
-		if (add_parents_to_list(revs, commit, &list, NULL) < 0)
+		if (process_parents(revs, commit, &list, NULL) < 0)
 			return -1;
 		if (obj->flags & UNINTERESTING) {
 			mark_parents_uninteresting(commit);
@@ -2468,7 +2472,7 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	if (revs->diffopt.objfind)
 		revs->simplify_history = 0;
 
-	if (revs->topo_order)
+	if (revs->topo_order && !generation_numbers_enabled(the_repository))
 		revs->limited = 1;
 
 	if (revs->prune_data.nr) {
@@ -2907,6 +2911,217 @@ static int mark_uninteresting(const struct object_id *oid,
 	return 0;
 }
 
+define_commit_slab(indegree_slab, int);
+define_commit_slab(author_date_slab, timestamp_t);
+
+struct topo_walk_info {
+	uint32_t min_generation;
+	struct prio_queue explore_queue;
+	struct prio_queue indegree_queue;
+	struct prio_queue topo_queue;
+	struct indegree_slab indegree;
+	struct author_date_slab author_date;
+};
+
+static inline void test_flag_and_insert(struct prio_queue *q, struct commit *c, int flag)
+{
+	if (c->object.flags & flag)
+		return;
+
+	c->object.flags |= flag;
+	prio_queue_put(q, c);
+}
+
+static void explore_walk_step(struct rev_info *revs)
+{
+	struct topo_walk_info *info = revs->topo_walk_info;
+	struct commit_list *p;
+	struct commit *c = prio_queue_get(&info->explore_queue);
+
+	if (!c)
+		return;
+
+	if (parse_commit_gently(c, 1) < 0)
+		return;
+
+	if (revs->sort_order == REV_SORT_BY_AUTHOR_DATE)
+		record_author_date(&info->author_date, c);
+
+	if (revs->max_age != -1 && (c->date < revs->max_age))
+		c->object.flags |= UNINTERESTING;
+
+	if (process_parents(revs, c, NULL, NULL) < 0)
+		return;
+
+	if (c->object.flags & UNINTERESTING)
+		mark_parents_uninteresting(c);
+
+	for (p = c->parents; p; p = p->next)
+		test_flag_and_insert(&info->explore_queue, p->item, TOPO_WALK_EXPLORED);
+}
+
+static void explore_to_depth(struct rev_info *revs,
+			     uint32_t gen_cutoff)
+{
+	struct topo_walk_info *info = revs->topo_walk_info;
+	struct commit *c;
+	while ((c = prio_queue_peek(&info->explore_queue)) &&
+	       c->generation >= gen_cutoff)
+		explore_walk_step(revs);
+}
+
+static void indegree_walk_step(struct rev_info *revs)
+{
+	struct commit_list *p;
+	struct topo_walk_info *info = revs->topo_walk_info;
+	struct commit *c = prio_queue_get(&info->indegree_queue);
+
+	if (!c)
+		return;
+
+	if (parse_commit_gently(c, 1) < 0)
+		return;
+
+	explore_to_depth(revs, c->generation);
+
+	for (p = c->parents; p; p = p->next) {
+		struct commit *parent = p->item;
+		int *pi = indegree_slab_at(&info->indegree, parent);
+
+		if (*pi)
+			(*pi)++;
+		else
+			*pi = 2;
+
+		test_flag_and_insert(&info->indegree_queue, parent, TOPO_WALK_INDEGREE);
+
+		if (revs->first_parent_only)
+			return;
+	}
+}
+
+static void compute_indegrees_to_depth(struct rev_info *revs,
+				       uint32_t gen_cutoff)
+{
+	struct topo_walk_info *info = revs->topo_walk_info;
+	struct commit *c;
+	while ((c = prio_queue_peek(&info->indegree_queue)) &&
+	       c->generation >= gen_cutoff)
+		indegree_walk_step(revs);
+}
+
+static void init_topo_walk(struct rev_info *revs)
+{
+	struct topo_walk_info *info;
+	struct commit_list *list;
+	revs->topo_walk_info = xmalloc(sizeof(struct topo_walk_info));
+	info = revs->topo_walk_info;
+	memset(info, 0, sizeof(struct topo_walk_info));
+
+	init_indegree_slab(&info->indegree);
+	memset(&info->explore_queue, 0, sizeof(info->explore_queue));
+	memset(&info->indegree_queue, 0, sizeof(info->indegree_queue));
+	memset(&info->topo_queue, 0, sizeof(info->topo_queue));
+
+	switch (revs->sort_order) {
+	default: /* REV_SORT_IN_GRAPH_ORDER */
+		info->topo_queue.compare = NULL;
+		break;
+	case REV_SORT_BY_COMMIT_DATE:
+		info->topo_queue.compare = compare_commits_by_commit_date;
+		break;
+	case REV_SORT_BY_AUTHOR_DATE:
+		init_author_date_slab(&info->author_date);
+		info->topo_queue.compare = compare_commits_by_author_date;
+		info->topo_queue.cb_data = &info->author_date;
+		break;
+	}
+
+	info->explore_queue.compare = compare_commits_by_gen_then_commit_date;
+	info->indegree_queue.compare = compare_commits_by_gen_then_commit_date;
+
+	info->min_generation = GENERATION_NUMBER_INFINITY;
+	for (list = revs->commits; list; list = list->next) {
+		struct commit *c = list->item;
+
+		if (parse_commit_gently(c, 1))
+			continue;
+
+		test_flag_and_insert(&info->explore_queue, c, TOPO_WALK_EXPLORED);
+		test_flag_and_insert(&info->indegree_queue, c, TOPO_WALK_INDEGREE);
+
+		if (c->generation < info->min_generation)
+			info->min_generation = c->generation;
+
+		*(indegree_slab_at(&info->indegree, c)) = 1;
+
+		if (revs->sort_order == REV_SORT_BY_AUTHOR_DATE)
+			record_author_date(&info->author_date, c);
+	}
+	compute_indegrees_to_depth(revs, info->min_generation);
+
+	for (list = revs->commits; list; list = list->next) {
+		struct commit *c = list->item;
+
+		if (*(indegree_slab_at(&info->indegree, c)) == 1)
+			prio_queue_put(&info->topo_queue, c);
+	}
+
+	/*
+	 * This is unfortunate; the initial tips need to be shown
+	 * in the order given from the revision traversal machinery.
+	 */
+	if (revs->sort_order == REV_SORT_IN_GRAPH_ORDER)
+		prio_queue_reverse(&info->topo_queue);
+}
+
+static struct commit *next_topo_commit(struct rev_info *revs)
+{
+	struct commit *c;
+	struct topo_walk_info *info = revs->topo_walk_info;
+
+	/* pop next off of topo_queue */
+	c = prio_queue_get(&info->topo_queue);
+
+	if (c)
+		*(indegree_slab_at(&info->indegree, c)) = 0;
+
+	return c;
+}
+
+static void expand_topo_walk(struct rev_info *revs, struct commit *commit)
+{
+	struct commit_list *p;
+	struct topo_walk_info *info = revs->topo_walk_info;
+	if (process_parents(revs, commit, NULL, NULL) < 0) {
+		if (!revs->ignore_missing_links)
+			die("Failed to traverse parents of commit %s",
+			    oid_to_hex(&commit->object.oid));
+	}
+
+	for (p = commit->parents; p; p = p->next) {
+		struct commit *parent = p->item;
+		int *pi;
+
+		if (parse_commit_gently(parent, 1) < 0)
+			continue;
+
+		if (parent->generation < info->min_generation) {
+			info->min_generation = parent->generation;
+			compute_indegrees_to_depth(revs, info->min_generation);
+		}
+
+		pi = indegree_slab_at(&info->indegree, parent);
+
+		(*pi)--;
+		if (*pi == 1)
+			prio_queue_put(&info->topo_queue, parent);
+
+		if (revs->first_parent_only)
+			return;
+	}
+}
+
 int prepare_revision_walk(struct rev_info *revs)
 {
 	int i;
@@ -2943,11 +3158,13 @@ int prepare_revision_walk(struct rev_info *revs)
 		commit_list_sort_by_date(&revs->commits);
 	if (revs->no_walk)
 		return 0;
-	if (revs->limited)
+	if (revs->limited) {
 		if (limit_list(revs) < 0)
 			return -1;
-	if (revs->topo_order)
-		sort_in_topological_order(&revs->commits, revs->sort_order);
+		if (revs->topo_order)
+			sort_in_topological_order(&revs->commits, revs->sort_order);
+	} else if (revs->topo_order)
+		init_topo_walk(revs);
 	if (revs->line_level_traverse)
 		line_log_filter(revs);
 	if (revs->simplify_merges)
@@ -2964,7 +3181,7 @@ static enum rewrite_result rewrite_one(struct rev_info *revs, struct commit **pp
 	for (;;) {
 		struct commit *p = *pp;
 		if (!revs->limited)
-			if (add_parents_to_list(revs, p, &revs->commits, &cache) < 0)
+			if (process_parents(revs, p, &revs->commits, &cache) < 0)
 				return rewrite_one_error;
 		if (p->object.flags & UNINTERESTING)
 			return rewrite_one_ok;
@@ -3272,6 +3489,8 @@ static struct commit *get_revision_1(struct rev_info *revs)
 
 		if (revs->reflog_info)
 			commit = next_reflog_entry(revs->reflog_info);
+		else if (revs->topo_walk_info)
+			commit = next_topo_commit(revs);
 		else
 			commit = pop_commit(&revs->commits);
 
@@ -3293,7 +3512,9 @@ static struct commit *get_revision_1(struct rev_info *revs)
 
 			if (revs->reflog_info)
 				try_to_simplify_commit(revs, commit);
-			else if (add_parents_to_list(revs, commit, &revs->commits, NULL) < 0) {
+			else if (revs->topo_walk_info)
+				expand_topo_walk(revs, commit);
+			else if (process_parents(revs, commit, &revs->commits, NULL) < 0) {
 				if (!revs->ignore_missing_links)
 					die("Failed to traverse parents of commit %s",
 						oid_to_hex(&commit->object.oid));
diff --git a/revision.h b/revision.h
index 0d2abc2d36..7987bfcd2e 100644
--- a/revision.h
+++ b/revision.h
@@ -32,6 +32,9 @@
 #define TRACK_LINEAR	(1u<<26)
 #define ALL_REV_FLAGS	(((1u<<11)-1) | NOT_USER_GIVEN | TRACK_LINEAR)
 
+#define TOPO_WALK_EXPLORED	(1u<<27)
+#define TOPO_WALK_INDEGREE	(1u<<28)
+
 #define DECORATE_SHORT_REFS	1
 #define DECORATE_FULL_REFS	2
 
@@ -64,6 +67,8 @@ struct rev_cmdline_info {
 #define REVISION_WALK_NO_WALK_SORTED 1
 #define REVISION_WALK_NO_WALK_UNSORTED 2
 
+struct topo_walk_info;
+
 struct rev_info {
 	/* Starting list */
 	struct commit_list *commits;
@@ -270,6 +275,8 @@ struct rev_info {
 	const char *break_bar;
 
 	struct revision_sources *sources;
+
+	struct topo_walk_info *topo_walk_info;
 };
 
 int ref_excluded(struct string_list *, const char *path);
diff --git a/t/helper/test-prio-queue.c b/t/helper/test-prio-queue.c
index 9807b649b1..5bc9c46ea5 100644
--- a/t/helper/test-prio-queue.c
+++ b/t/helper/test-prio-queue.c
@@ -22,14 +22,24 @@ int cmd__prio_queue(int argc, const char **argv)
 	struct prio_queue pq = { intcmp };
 
 	while (*++argv) {
-		if (!strcmp(*argv, "get"))
-			show(prio_queue_get(&pq));
-		else if (!strcmp(*argv, "dump")) {
-			int *v;
-			while ((v = prio_queue_get(&pq)))
-			       show(v);
-		}
-		else {
+		if (!strcmp(*argv, "get")) {
+			void *peek = prio_queue_peek(&pq);
+			void *get = prio_queue_get(&pq);
+			if (peek != get)
+				BUG("peek and get results do not match");
+			show(get);
+		} else if (!strcmp(*argv, "dump")) {
+			void *peek;
+			void *get;
+			while ((peek = prio_queue_peek(&pq))) {
+				get = prio_queue_get(&pq);
+				if (peek != get)
+					BUG("peek and get results do not match");
+				show(get);
+			}
+		} else if (!strcmp(*argv, "stack")) {
+			pq.compare = NULL;
+		} else {
 			int *v = malloc(sizeof(*v));
 			*v = atoi(*argv);
 			prio_queue_put(&pq, v);
diff --git a/t/t0009-prio-queue.sh b/t/t0009-prio-queue.sh
index e56dfce668..3941ad2528 100755
--- a/t/t0009-prio-queue.sh
+++ b/t/t0009-prio-queue.sh
@@ -47,4 +47,18 @@ test_expect_success 'notice empty queue' '
 	test_cmp expect actual
 '
 
+cat >expect <<'EOF'
+3
+2
+6
+4
+5
+1
+8
+EOF
+test_expect_success 'stack order' '
+	test-tool prio-queue stack 8 1 5 4 6 2 3 dump >actual &&
+	test_cmp expect actual
+'
+
 test_done
diff --git a/t/t6012-rev-list-simplify.sh b/t/t6012-rev-list-simplify.sh
index b5a1190ffe..a10f0df02b 100755
--- a/t/t6012-rev-list-simplify.sh
+++ b/t/t6012-rev-list-simplify.sh
@@ -12,6 +12,22 @@ unnote () {
 	git name-rev --tags --stdin | sed -e "s|$OID_REGEX (tags/\([^)]*\)) |\1 |g"
 }
 
+#
+# Create a test repo with interesting commit graph:
+#
+# A--B----------G--H--I--K--L
+#  \  \           /     /
+#   \  \         /     /
+#    C------E---F     J
+#        \_/
+#
+# The commits are laid out from left-to-right starting with
+# the root commit A and terminating at the tip commit L.
+#
+# There are a few places where we adjust the commit date or
+# author date to make the --topo-order, --date-order, and
+# --author-date-order flags produce different output.
+
 test_expect_success setup '
 	echo "Hi there" >file &&
 	echo "initial" >lost &&
@@ -21,10 +37,18 @@ test_expect_success setup '
 
 	git branch other-branch &&
 
+	git symbolic-ref HEAD refs/heads/unrelated &&
+	git rm -f "*" &&
+	echo "Unrelated branch" >side &&
+	git add side &&
+	test_tick && git commit -m "Side root" &&
+	note J &&
+	git checkout master &&
+
 	echo "Hello" >file &&
 	echo "second" >lost &&
 	git add file lost &&
-	test_tick && git commit -m "Modified file and lost" &&
+	test_tick && GIT_AUTHOR_DATE=$(($test_tick + 120)) git commit -m "Modified file and lost" &&
 	note B &&
 
 	git checkout other-branch &&
@@ -63,13 +87,6 @@ test_expect_success setup '
 	test_tick && git commit -a -m "Final change" &&
 	note I &&
 
-	git symbolic-ref HEAD refs/heads/unrelated &&
-	git rm -f "*" &&
-	echo "Unrelated branch" >side &&
-	git add side &&
-	test_tick && git commit -m "Side root" &&
-	note J &&
-
 	git checkout master &&
 	test_tick && git merge --allow-unrelated-histories -m "Coolest" unrelated &&
 	note K &&
@@ -103,14 +120,24 @@ check_result () {
 	check_outcome success "$@"
 }
 
-check_result 'L K J I H G F E D C B A' --full-history
+check_result 'L K J I H F E D C G B A' --full-history --topo-order
+check_result 'L K I H G F E D C B J A' --full-history
+check_result 'L K I H G F E D C B J A' --full-history --date-order
+check_result 'L K I H G F E D B C J A' --full-history --author-date-order
 check_result 'K I H E C B A' --full-history -- file
 check_result 'K I H E C B A' --full-history --topo-order -- file
 check_result 'K I H E C B A' --full-history --date-order -- file
+check_result 'K I H E B C A' --full-history --author-date-order -- file
 check_result 'I E C B A' --simplify-merges -- file
+check_result 'I E C B A' --simplify-merges --topo-order -- file
+check_result 'I E C B A' --simplify-merges --date-order -- file
+check_result 'I E B C A' --simplify-merges --author-date-order -- file
 check_result 'I B A' -- file
 check_result 'I B A' --topo-order -- file
+check_result 'I B A' --date-order -- file
+check_result 'I B A' --author-date-order -- file
 check_result 'H' --first-parent -- another-file
+check_result 'H' --first-parent --topo-order -- another-file
 
 check_result 'E C B A' --full-history E -- lost
 test_expect_success 'full history simplification without parent' '
diff --git a/t/t6600-test-reach.sh b/t/t6600-test-reach.sh
index a0c64e617a..b24d850036 100755
--- a/t/t6600-test-reach.sh
+++ b/t/t6600-test-reach.sh
@@ -56,18 +56,22 @@ test_expect_success 'setup' '
 	git config core.commitGraph true
 '
 
-test_three_modes () {
+run_three_modes () {
 	test_when_finished rm -rf .git/objects/info/commit-graph &&
-	test-tool reach $1 <input >actual &&
+	"$@" <input >actual &&
 	test_cmp expect actual &&
 	cp commit-graph-full .git/objects/info/commit-graph &&
-	test-tool reach $1 <input >actual &&
+	"$@" <input >actual &&
 	test_cmp expect actual &&
 	cp commit-graph-half .git/objects/info/commit-graph &&
-	test-tool reach $1 <input >actual &&
+	"$@" <input >actual &&
 	test_cmp expect actual
 }
 
+test_three_modes () {
+	run_three_modes test-tool reach "$@"
+}
+
 test_expect_success 'ref_newer:miss' '
 	cat >input <<-\EOF &&
 	A:commit-5-7
@@ -265,6 +269,90 @@ test_expect_success 'commit_contains:miss' '
 	test_three_modes commit_contains --tag
 '
 
+test_expect_success 'rev-list: basic topo-order' '
+	git rev-parse \
+		commit-6-6 commit-5-6 commit-4-6 commit-3-6 commit-2-6 commit-1-6 \
+		commit-6-5 commit-5-5 commit-4-5 commit-3-5 commit-2-5 commit-1-5 \
+		commit-6-4 commit-5-4 commit-4-4 commit-3-4 commit-2-4 commit-1-4 \
+		commit-6-3 commit-5-3 commit-4-3 commit-3-3 commit-2-3 commit-1-3 \
+		commit-6-2 commit-5-2 commit-4-2 commit-3-2 commit-2-2 commit-1-2 \
+		commit-6-1 commit-5-1 commit-4-1 commit-3-1 commit-2-1 commit-1-1 \
+	>expect &&
+	run_three_modes git rev-list --topo-order commit-6-6
+'
+
+test_expect_success 'rev-list: first-parent topo-order' '
+	git rev-parse \
+		commit-6-6 \
+		commit-6-5 \
+		commit-6-4 \
+		commit-6-3 \
+		commit-6-2 \
+		commit-6-1 commit-5-1 commit-4-1 commit-3-1 commit-2-1 commit-1-1 \
+	>expect &&
+	run_three_modes git rev-list --first-parent --topo-order commit-6-6
+'
+
+test_expect_success 'rev-list: range topo-order' '
+	git rev-parse \
+		commit-6-6 commit-5-6 commit-4-6 commit-3-6 commit-2-6 commit-1-6 \
+		commit-6-5 commit-5-5 commit-4-5 commit-3-5 commit-2-5 commit-1-5 \
+		commit-6-4 commit-5-4 commit-4-4 commit-3-4 commit-2-4 commit-1-4 \
+		commit-6-3 commit-5-3 commit-4-3 \
+		commit-6-2 commit-5-2 commit-4-2 \
+		commit-6-1 commit-5-1 commit-4-1 \
+	>expect &&
+	run_three_modes git rev-list --topo-order commit-3-3..commit-6-6
+'
+
+test_expect_success 'rev-list: range topo-order' '
+	git rev-parse \
+		commit-6-6 commit-5-6 commit-4-6 \
+		commit-6-5 commit-5-5 commit-4-5 \
+		commit-6-4 commit-5-4 commit-4-4 \
+		commit-6-3 commit-5-3 commit-4-3 \
+		commit-6-2 commit-5-2 commit-4-2 \
+		commit-6-1 commit-5-1 commit-4-1 \
+	>expect &&
+	run_three_modes git rev-list --topo-order commit-3-8..commit-6-6
+'
+
+test_expect_success 'rev-list: first-parent range topo-order' '
+	git rev-parse \
+		commit-6-6 \
+		commit-6-5 \
+		commit-6-4 \
+		commit-6-3 \
+		commit-6-2 \
+		commit-6-1 commit-5-1 commit-4-1 \
+	>expect &&
+	run_three_modes git rev-list --first-parent --topo-order commit-3-8..commit-6-6
+'
+
+test_expect_success 'rev-list: ancestry-path topo-order' '
+	git rev-parse \
+		commit-6-6 commit-5-6 commit-4-6 commit-3-6 \
+		commit-6-5 commit-5-5 commit-4-5 commit-3-5 \
+		commit-6-4 commit-5-4 commit-4-4 commit-3-4 \
+		commit-6-3 commit-5-3 commit-4-3 \
+	>expect &&
+	run_three_modes git rev-list --topo-order --ancestry-path commit-3-3..commit-6-6
+'
+
+test_expect_success 'rev-list: symmetric difference topo-order' '
+	git rev-parse \
+		commit-6-6 commit-5-6 commit-4-6 \
+		commit-6-5 commit-5-5 commit-4-5 \
+		commit-6-4 commit-5-4 commit-4-4 \
+		commit-6-3 commit-5-3 commit-4-3 \
+		commit-6-2 commit-5-2 commit-4-2 \
+		commit-6-1 commit-5-1 commit-4-1 \
+		commit-3-8 commit-2-8 commit-1-8 \
+		commit-3-7 commit-2-7 commit-1-7 \
+	>expect &&
+	run_three_modes git rev-list --topo-order commit-3-8...commit-6-6
+'
+
 test_expect_success 'get_reachable_subset:all' '
 	cat >input <<-\EOF &&
 	X:commit-9-1