diff -r e4d3370fa234 -r 5fb3cb7266e5 mercurial/config.py
--- a/mercurial/config.py	Mon Jun 20 09:30:03 2011 +0200
+++ b/mercurial/config.py	Mon Jun 20 10:51:37 2011 +0200
@@ -27,6 +27,9 @@
     def update(self, src):
         for k in src:
             self[k] = src[k]
+    def clear(self):
+        dict.clear(self)
+        self._list = []
     def items(self):
         return [(k, self[k]) for k in self._list]
     def __delitem__(self, key):