context: add __contains__, __getitem__, and __iter__

mercurial/context.py

@@ -60,6 +60,18 b' class changectx(object):'
         else:
             raise AttributeError, name
 
+    def __contains__(self, key):
+        return key in self._manifest
+
+    def __getitem__(self, key):
+        return self.filectx(key)
+
+    def __iter__(self):
+        a = self._manifest.keys()
+        a.sort()
+        for f in a:
+            return f
+
     def changeset(self): return self._changeset
     def manifest(self): return self._manifest