# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2014-08-15 22:57:50
# Node ID baecf4e1b7d02f62b368515bf07f5239b10ab9b9
# Parent  f713de1d391664614add55577d71e9b52ff328a7

ancestors: add a __nonzero__ method

This allows using the object in a conditional the same way we can use list.

diff --git a/mercurial/ancestor.py b/mercurial/ancestor.py
--- a/mercurial/ancestor.py
+++ b/mercurial/ancestor.py
@@ -246,6 +246,14 @@ class lazyancestors(object):
         else:
             self._containsseen = set()
 
+    def __nonzero__(self):
+        """False if the set is empty, True otherwise."""
+        try:
+            iter(self).next()
+            return True
+        except StopIteration:
+            return False
+
     def __iter__(self):
         """Generate the ancestors of _initrevs in reverse topological order.