namespaces: add __getitem__ property

Since the namespaces object uses an underlying (sorted) dictionary to store the
namespaces, it makes sense to expose this to naturally gain access to those
namespaces.

mercurial/namespaces.py

@@ -42,6 +42,10 b' class namespaces(object):'
                lambda repo, node: [repo[node].branch()])
         self.addnamespace(n)
 
+    def __getitem__(self, namespace):
+        """returns the namespace object"""
+        return self._names[namespace]
+
     def addnamespace(self, namespace, order=None):
         """register a namespace