module AbstractController::Callbacks::ClassMethods

* except - The callback should be run for all actions except this action
* only - The callback should be run only for this action
==== Options

:if => proc {|c| c.action_name == "index" }.
The basic idea is that :only => :index gets converted to
:unless and :if options of ActiveSupport::Callbacks.
If :only or :except are used, convert the options into the

def _normalize_callback_options(options)
  _normalize_callback_option(options, :only, :if)
  _normalize_callback_option(options, :except, :unless)
end