Best way to get buffer changes in a program?

[Thorsten Jolitz]

Hi List, 

there are many ways to track and visualize changes in Emacs (see
e.g. http://www.emacswiki.org/emacs/TrackChanges). 

However, I would like to get non-interactively a list of lines (or
positions) in the buffer that changed after the last command - how to I
do that? Is is somehow possible to determine in a program that calls
other functions that insert text which new lines have been inserted (when
a buffer increased in size after a command was executed)?

Thanks in advance for any hints.

-- 
cheers,
Thorsten