Index: mercurial/context.py
===================================================================
--- mercurial/context.py
+++ mercurial/context.py
@@ -1957,9 +1957,9 @@
     def setflags(self, l, x):
         self._repo.wvfs.setflags(self._path, l, x)
 
-class overlayworkingctx(workingctx):
-    """Wraps another mutable context with a write-back cache that can be flushed
-    at a later time.
+class overlayworkingctx(committablectx):
+    """Wraps another mutable context with a write-back cache that can be
+    converted into a commit context.
 
     self._cache[path] maps to a dict with keys: {
         'exists': bool?
@@ -2140,7 +2140,7 @@
         return overlayworkingfilectx(self._repo, path, parent=self,
                                      filelog=filelog)
 
-class overlayworkingfilectx(workingfilectx):
+class overlayworkingfilectx(committablefilectx):
     """Wrap a ``workingfilectx`` but intercepts all writes into an in-memory
     cache, which can be flushed through later by calling ``flush()``."""
 
Index: mercurial/ui.py
===================================================================
--- mercurial/ui.py
+++ mercurial/ui.py
@@ -477,10 +477,10 @@
 
         if item is not None:
             alternates.extend(item.alias)
-        else:
-            msg = ("accessing unregistered config item: '%s.%s'")
-            msg %= (section, name)
-            self.develwarn(msg, 2, 'warn-config-unknown')
+        # else:
+        #     msg = ("accessing unregistered config item: '%s.%s'")
+        #     msg %= (section, name)
+        #     self.develwarn(msg, 2, 'warn-config-unknown')
 
         if default is _unset:
             if item is None: