[OS X Emacs] Emacs for revisions/Track Changes?

[Carsten Bormann]

I think you will be interested in the concept of revision control systems.
Emacs has a lot of very well thought out support for those, including a way to call "ediff" mode using "ediff-revisions".

Learn more about revision control systems (version control systems, source code control systems, ...) at
http://en.wikipedia.org/wiki/Revision_control

The most popular current-generation version control system is git.
Find a great introduction at:
http://git-scm.com/book

Also still popular is the previous-generation system subversion.
http://svnbook.red-bean.com/

Grüße, Carsten