configitems: extract the logic to build a registrar on any configtable

Having the logic available independently from the mapping used is a necessary
step toward extensions support.

mercurial/configitems.py

@@ -1,50 +1,57 b''
 # configitems.py - centralized declaration of configuration option
 #
 #  Copyright 2017 Pierre-Yves David <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
+import functools
+
 from . import (
     error,
 )
 
 class configitem(object):
     """represent a known config item
 
     :section: the official config section where to find this item,
        :name: the official name within the section,
     :default: default value for this item,
     """
 
     def __init__(self, section, name, default=None):
         self.section = section
         self.name = name
         self.default = default
 
 coreitems = {}
 
-def coreconfigitem(*args, **kwargs):
+def _register(configtable, *args, **kwargs):
     item = configitem(*args, **kwargs)
-    section = coreitems.setdefault(item.section, {})
+    section = configtable.setdefault(item.section, {})
     if item.name in section:
         msg = "duplicated config item registration for '%s.%s'"
         raise error.ProgrammingError(msg % (item.section, item.name))
     section[item.name] = item
 
 # Registering actual config items
 
+def getitemregister(configtable):
+    return functools.partial(_register, configtable)
+
+coreconfigitem = getitemregister(coreitems)
+
 coreconfigitem('patch', 'fuzz',
     default=2,
 )
 coreconfigitem('ui', 'clonebundleprefers',
     default=[],
 )
 coreconfigitem('ui', 'interactive',
     default=None,
 )
 coreconfigitem('ui', 'quiet',
     default=False,
 )