diff -r 5a84a453b503 -r d3712209921d mercurial/templater.py
--- a/mercurial/templater.py	Mon Oct 05 10:43:16 2015 -0600
+++ b/mercurial/templater.py	Thu Oct 08 23:24:38 2015 +0900
@@ -227,8 +227,6 @@
             v = ''
     if callable(v):
         return v(**mapping)
-    if isinstance(v, types.GeneratorType):
-        v = list(v)
     return v
 
 def buildtemplate(exp, context):