diff -r a9de1d28681c -r f9c426385853 mercurial/hgweb/webutil.py
--- a/mercurial/hgweb/webutil.py	Tue Jun 12 23:17:38 2018 +0900
+++ b/mercurial/hgweb/webutil.py	Sat Jun 09 13:34:47 2018 +0900
@@ -743,6 +743,9 @@
     def show(self, context, mapping):
         return self.join(context, '')
 
+    def tobool(self, context, mapping):
+        return bool(self._vars)
+
     def tovalue(self, context, mapping):
         return self._vars