diff -r 28a4fb793ba1 -r 70ca0e846d25 mercurial/exthelper.py
--- a/mercurial/exthelper.py	Thu Dec 27 21:46:03 2018 -0500
+++ b/mercurial/exthelper.py	Thu Dec 27 21:55:22 2018 -0500
@@ -41,6 +41,7 @@
         self.configtable = {}
         self.configitem = registrar.configitem(self.configtable)
         self.revsetpredicate = registrar.revsetpredicate()
+        self.templatekeyword = registrar.templatekeyword()
 
     def merge(self, other):
         self._uicallables.extend(other._uicallables)
@@ -48,6 +49,7 @@
         self._extcallables.extend(other._extcallables)
         self._repocallables.extend(other._repocallables)
         self.revsetpredicate._table.update(other.revsetpredicate._table)
+        self.templatekeyword._table.update(other.templatekeyword._table)
         self._commandwrappers.extend(other._commandwrappers)
         self._extcommandwrappers.extend(other._extcommandwrappers)
         self._functionwrappers.extend(other._functionwrappers)