[PATCH] revset: fix infinite recursion if called with __len__ first

[Maciej Fijalkowski]

# HG changeset patch
# User Maciej Fijalkowski <fijall at gmail.com>
# Date 1459435465 -7200
#      Thu Mar 31 16:44:25 2016 +0200
# Node ID eaaeff1b98571b90ec71614c75126e64e98c004b
# Parent  ff0d3b6b287f89594bd8d0308fe2810d2a18ea01
revset: fix infinite recursion if called with __len__ first

The problem here is simple - set(x) can (but doesn't have to) call
__len__ first. If we do that, __len__ calls set which calls __len__
again and we end up with inifinite recursion that gets swallowed and
gets interesting results. Call it properly on the subset instead,
fixes test-bisect2.t on PyPy

diff -r ff0d3b6b287f -r eaaeff1b9857 mercurial/revset.py
--- a/mercurial/revset.py	Tue Mar 29 12:29:00 2016 -0500
+++ b/mercurial/revset.py	Thu Mar 31 16:44:25 2016 +0200
@@ -3020,7 +3020,7 @@
 
     def __len__(self):
         # Basic implementation to be changed in future patches.
-        l = baseset([r for r in self])
+        l = baseset([r for r in self._subset if self._condition(r)])
         return len(l)
 
     def sort(self, reverse=False):