I think it is a relevant thing:

Idea link: http://groups.drupal.org/node/20472

Official proposal : http://groups.drupal.org/node/20605

I commented on the proposal node telling them about this module.

I suppose that this proposal (diffing) is the logical ancestor of checkout module - maybe we should merge this new functionality into checkout...

PS Are there existing contribs except checkout that address the same features?