diff -r 3ef6adad4e43 -r 76021ec849c8 mercurial/dirstate.py
--- a/mercurial/dirstate.py	Sat Jun 14 16:01:24 2008 +0200
+++ b/mercurial/dirstate.py	Sun Jun 15 13:05:39 2008 +0200
@@ -186,6 +186,8 @@
         self._dirty = False
 
     def copy(self, source, dest):
+        if source == dest:
+            return
         self._dirty = True
         self._copymap[dest] = source