--- a/mercurial/templater.py	Sat Aug 20 18:15:19 2016 +0900
+++ b/mercurial/templater.py	Fri Aug 19 18:26:04 2016 +0900
@@ -960,6 +960,9 @@
                 return True
         except error.RevlogError:
             return False
+        except error.WdirUnsupported:
+            # single 'ff...' match
+            return True
 
     shortest = node
     startlength = max(6, minlength)