--- a/mercurial/registrar.py	Mon Apr 03 20:55:55 2017 +0900
+++ b/mercurial/registrar.py	Mon Apr 03 21:22:39 2017 +0900
@@ -234,7 +234,7 @@
 
         templatefunc = registrar.templatefunc()
 
-        @templatefunc('myfunc(arg1, arg2[, arg3])')
+        @templatefunc('myfunc(arg1, arg2[, arg3])', argspec='arg1 arg2 arg3')
         def myfuncfunc(context, mapping, args):
             '''Explanation of this template function ....
             '''
@@ -242,6 +242,10 @@
 
     The first string argument is used also in online help.
 
+    If optional 'argspec' is defined, the function will receive 'args' as
+    a dict of named arguments. Otherwise 'args' is a list of positional
+    arguments.
+
     'templatefunc' instance in example above can be used to
     decorate multiple functions.
 
@@ -252,3 +256,6 @@
     Otherwise, explicit 'templater.loadfunction()' is needed.
     """
     _getname = _funcregistrarbase._parsefuncdecl
+
+    def _extrasetup(self, name, func, argspec=None):
+        func._argspec = argspec