[PATCH 1 of 3] registrar: add templatekeyword to mark a function as template keyword (API)

[Yuya Nishihara]

On Sun, 13 Mar 2016 22:57:56 +0900, FUJIWARA Katsunori wrote:
>     # code for portability >>>>
>     try:
>         from mercurial import registrar
>         if not util.safehasattr(registrar, 'templatekeyword'):
>             raise ImportError()
> 
>         templatekeyword = registrar.templatekeyword()
>         loadkeyword = lambda registrarobj: None # nop
>     except ImportError:
>         # registrar.templatekeyword isn't available = loading by old hg
> 
>         # minimum copy from registrar._funcregistrarbase
>         class _funcregistrarbase(object):
>             ....
> 
>         templatekeyword = _funcregistrarbase()
>         templatekeyword._docformat = ":%s: %s"
> 
>         # minimum copy from templatekw.loadkeyword
>         def loadkeyword(registrarobj):
>             from mercurial import templatekw
>             for name, func in registrarobj._table.iteritems():
>                 templatekw.keywords[name] = func
>     # <<<< code for portability

or simply use noop decorator:

    _registrarloaded = False
    try:
        from mercurial import registrar
        templatekeyword = registrar.templatekeyword()
        _registrarloaded = True
    except (ImportError, AttributeError):
        def templatekeyword(decl):
            return lambda func: func

    def extsetup(ui):
        if not _registrarloaded:
            templatekw.keywords['foo'] = kwfoo