topfunky/google-checkout — pull request #7 by jamesotron (2012-05-17 02:36:33+00:00)
Title: Add the notification serial number to the acknowedgment_xml.

As per [the docs](https://developers.google.com/checkout/developer/Google_Checkout_XML_API_Notification_API#notification_response_handshake) Google requires the XML acknowledgment to include the serial number of the request being acknowledged.