--- a/mercurial/revset.py	Thu Mar 06 09:41:47 2014 -0800
+++ b/mercurial/revset.py	Fri Mar 14 09:07:59 2014 -0700
@@ -2490,6 +2490,11 @@
         return self._contained(x) and not (self._hiddenrevs and rev in
                 self._hiddenrevs)
 
+    def __nonzero__(self):
+        for r in self:
+            return True
+        return False
+
     def __and__(self, x):
         if isinstance(x, baseset):
             x = x.set()