From 2cc42f78929ba1815853be181d3b16da7c05f811 Mon Sep 17 00:00:00 2001
From: =?utf8?q?=C5=81ukasz=20Langa?= <lukasz@langa.pl>
Date: Sat, 9 Jun 2018 19:49:20 -0700
Subject: [PATCH] Don't mark subtrees as changed that were already marked.

---
 blib2to3/pytree.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/blib2to3/pytree.py b/blib2to3/pytree.py
index b24866e..61df2b6 100644
--- a/blib2to3/pytree.py
+++ b/blib2to3/pytree.py
@@ -132,6 +132,8 @@ class Base(object):
         return node.lineno
 
     def changed(self):
+        if self.was_changed:
+            return
         if self.parent:
             self.parent.changed()
         self.was_changed = True
-- 
2.39.5