'Return a zsh "action" string for the given argument
@return: C{str}'

def getAction(self, longname):

    if (longname in self.optActions):
        if callable(self.optActions[longname]):
            action = self.optActions[longname]()
        else:
            action = self.optActions[longname]
        return action._shellCode(longname, usage._ZSH)
    if (longname in self.paramNameToDefinition):
        return (':%s:_files' % (longname,))
    return ''
