mercurial/revset.py

--- a/mercurial/revset.py	Fri Mar 14 09:18:14 2014 -0700
+++ b/mercurial/revset.py	Thu Mar 13 19:12:36 2014 -0700
@@ -2392,6 +2392,11 @@
             self._genlist = baseset(self._iterator())
         return self._genlist
 
+    def filter(self, condition):
+        if self._ascending is not None:
+            return orderedlazyset(self, condition, ascending=self._ascending)
+        return lazyset(self, condition)
+
     def _iterator(self):
         """Iterate over both collections without repeating elements