revision.c: treat A...B merge bases as if manually specified

The documentation assures users that "A...B" is defined as "A B --not
$(git merge-base --all A B)". This wasn't in fact quite true, because
the calculated merge bases were not sent to add_rev_cmdline().

The main effect of this was that although

  git rev-list --ancestry-path A B --not $(git merge-base --all A B)

worked, the simpler form

  git rev-list --ancestry-path A...B

failed with a "no bottom commits" error.

Other potential users of bottom commits could also be affected by this
problem, if they examine revs->cmdline_info; I came across the issue in
my proposed history traversal refinements series.

So ensure that the calculated merge bases are sent to add_rev_cmdline(),
flagged with new 'whence' enum value REV_CMD_MERGE_BASE.

Signed-off-by: Kevin Bracey <kevin@bracey.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -915,6 +915,19 @@ static void add_rev_cmdline(struct rev_info *revs,
 	info->nr++;
 }
 
+static void add_rev_cmdline_list(struct rev_info *revs,
+				 struct commit_list *commit_list,
+				 int whence,
+				 unsigned flags)
+{
+	while (commit_list) {
+		struct object *object = &commit_list->item->object;
+		add_rev_cmdline(revs, object, sha1_to_hex(object->sha1),
+				whence, flags);
+		commit_list = commit_list->next;
+	}
+}
+
 struct all_refs_cb {
 	int all_flags;
 	int warned_bad_reflog;
@@ -1092,6 +1105,7 @@ static void prepare_show_merge(struct rev_info *revs)
 	add_pending_object(revs, &head->object, "HEAD");
 	add_pending_object(revs, &other->object, "MERGE_HEAD");
 	bases = get_merge_bases(head, other, 1);
+	add_rev_cmdline_list(revs, bases, REV_CMD_MERGE_BASE, UNINTERESTING);
 	add_pending_commit_list(revs, bases, UNINTERESTING);
 	free_commit_list(bases);
 	head->object.flags |= SYMMETRIC_LEFT;
@@ -1179,6 +1193,9 @@ int handle_revision_arg(const char *arg_, struct rev_info *revs, int flags, unsi
 
 			if (symmetric) {
 				exclude = get_merge_bases(a, b, 1);
+				add_rev_cmdline_list(revs, exclude,
+						     REV_CMD_MERGE_BASE,
+						     flags_exclude);
 				add_pending_commit_list(revs, exclude,
 							flags_exclude);
 				free_commit_list(exclude);

revision.h

@@ -35,6 +35,7 @@ struct rev_cmdline_info {
 			REV_CMD_PARENTS_ONLY,
 			REV_CMD_LEFT,
 			REV_CMD_RIGHT,
+			REV_CMD_MERGE_BASE,
 			REV_CMD_REV
 		} whence;
 		unsigned flags;

t/t6019-rev-list-ancestry-path.sh

@@ -81,7 +81,7 @@ test_expect_success 'rev-list F...I' '
 	test_cmp expect actual
 '
 
-test_expect_failure 'rev-list --ancestry-path F...I' '
+test_expect_success 'rev-list --ancestry-path F...I' '
 	for c in F H I; do echo $c; done >expect &&
 	git rev-list --ancestry-path --format=%s F...I |
 	sed -e "/^commit /d" |