context: move equivalent renamed() implementations to superclass

Now that renamed() in workingfilectx and in overlayfilectx are written
in terms of copysource(), they are functionally identical and can be
reused.

Differential Revision: https://phab.mercurial-scm.org/D6010

mercurial/context.py

@@ -1664,6 +1664,12 b' class committablefilectx(basefilectx):'
         # linked to self._changectx no matter if file is modified or not
         return self.rev()
 
+    def renamed(self):
+        path = self.copysource()
+        if not path:
+            return None
+        return path, self._changectx._parents[0]._manifest.get(path, nullid)
+
     def parents(self):
         '''return parent filectxs, following copies if necessary'''
         def filenode(ctx, path):
@@ -1700,11 +1706,6 b' class workingfilectx(committablefilectx)'
 
     def data(self):
         return self._repo.wread(self._path)
-    def renamed(self):
-        rp = self.copysource()
-        if not rp:
-            return None
-        return rp, self._changectx._parents[0]._manifest.get(rp, nullid)
     def copysource(self):
         return self._repo.dirstate.copied(self._path)
 
@@ -2146,12 +2147,6 b' class overlayworkingfilectx(committablef'
     def lexists(self):
         return self._parent.exists(self._path)
 
-    def renamed(self):
-        path = self.copysource()
-        if not path:
-            return None
-        return path, self._changectx._parents[0]._manifest.get(path, nullid)
-
     def copysource(self):
         return self._parent.copydata(self._path)