namespace: use registrar to add template keyword

Prepares for switching to the new API.

mercurial/namespaces.py

@@ -2,6 +2,7 b' from __future__ import absolute_import'
 
 from .i18n import _
 from . import (
+    registrar,
     templatekw,
     util,
 )
@@ -87,11 +88,11 b' class namespaces(object):'
 
         # we only generate a template keyword if one does not already exist
         if namespace.name not in templatekw.keywords:
+            templatekeyword = registrar.templatekeyword(templatekw.keywords)
+            @templatekeyword(namespace.name)
             def generatekw(**args):
                 return templatekw.shownames(namespace.name, **args)
 
-            templatekw.keywords[namespace.name] = generatekw
-
     def singlenode(self, repo, name):
         """
         Return the 'best' node for the given name. Best means the first node