WebDevStudios/Custom-Metaboxes-and-Fields-for-WordPress — pull request #611 by nikolov-tmw (2014-07-04 20:35:20+00:00)
Title: #588 - Add support for meta diffs

I've added two more arrays that contain the old and new values for all fields saved from within the metabox.
This is especially useful if you need to create a diff between the two states of the post meta - for instance when you have to send an email with a summary of the changes.

Looking forward to any comments/suggestions.