diff -r 2dd1cbee569d -r 293930a1fa0a mercurial/templatekw.py
--- a/mercurial/templatekw.py	Fri Sep 05 19:54:26 2014 +0200
+++ b/mercurial/templatekw.py	Mon Sep 08 20:12:58 2014 +0900
@@ -26,6 +26,8 @@
     def __call__(self):
         for x in self.values:
             yield x
+    def __len__(self):
+        return len(self.values)
 
 def showlist(name, values, plural=None, element=None, **args):
     if not element: