suppress errors on missing UNINTERESTING links

When we are traversing commit parents along the
UNINTERESTING side of a revision walk, we do not care if
the parent turns out to be missing. That lets us limit
traversals using unreachable and possibly incomplete
sections of history. However, we do still print error
messages about the missing commits; this patch suppresses
the error, as well.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

revision.c

@@ -807,7 +807,7 @@ static int add_parents_to_list(struct rev_info *revs, struct commit *commit,
 			parent = parent->next;
 			if (p)
 				p->object.flags |= UNINTERESTING;
-			if (parse_commit(p) < 0)
+			if (parse_commit_gently(p, 1) < 0)
 				continue;
 			if (p->parents)
 				mark_parents_uninteresting(p);