[PATCH 3 of 4 RFC] revset: added __nonzero__ method to lazyset

[Lucas Moscovicz]

# HG changeset patch
# User Lucas Moscovicz <lmoscovicz at fb.com>
# Date 1392920138 28800
#      Thu Feb 20 10:15:38 2014 -0800
# Node ID 44ca956d656db4e57add5e815dfd0aaaec57c6b9
# Parent  20cac5a92843ff52c2c4d0af45505cf9a303086b
revset: added __nonzero__ method to lazyset

Now it doesn't have to go through all the set and can return lazily as soon as
it finds one element.

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2143,6 +2143,11 @@
     def extend(self, x):
         self.append(x)
 
+    def __nonzero__(self):
+        for r in self:
+            return True
+        return False
+
     def __len__(self):
         # Basic implementation to be changed in future patches.
         l = baseset([r for r in self])