Don't recurse into parents marked uninteresting.

revision.c:make_parents_uninteresting() is exponential with the number
of merges in the tree. That's fine -- unless some other part of git
already has pulled the whole commit tree into memory ...

Signed-off-by: Junio C Hamano <junkio@cox.net>

revision.c

@@ -82,6 +82,7 @@ void mark_parents_uninteresting(struct commit *commit)
 
 	while (parents) {
 		struct commit *commit = parents->item;
+		if (!(commit->object.flags & UNINTERESTING)) {
 			commit->object.flags |= UNINTERESTING;
 
 			/*
@@ -94,6 +95,7 @@ void mark_parents_uninteresting(struct commit *commit)
 			 */
 			if (commit->parents)
 				mark_parents_uninteresting(commit);
+		}
 
 		/*
 		 * A missing commit is ok iff its parent is marked