namespaces: add __iter__ and iteritems methods

Iterating over all the namespaces is a common operation, naturally, so we add
those methods now. Since we are using a sorted dictionary, this method just
calls the underlying __iter__ or iteritems method.

mercurial/namespaces.py

@@ -49,6 +49,12 b' class namespaces(object):'
         """returns the namespace object"""
         return self._names[namespace]
 
+    def __iter__(self):
+        return self._names.__iter__()
+
+    def iteritems(self):
+        return self._names.iteritems()
+
     def addnamespace(self, namespace, order=None):
         """register a namespace