mercurial/context.py

--- a/mercurial/context.py	Mon Oct 16 13:10:55 2017 -0700
+++ b/mercurial/context.py	Fri Oct 13 12:34:22 2017 -0700
@@ -2098,6 +2098,9 @@
         self._parent = parent
         self._path = path
 
+    def cmp(self, fctx):
+        return self.data() != fctx.data()
+
     def ctx(self):
         return self._parent