Heres a handy script I wrote this morning, how do you easily see the differences between your mytheme_function override template.php entries and the original theme_function in the sites/all/modules, modules/, includes/ ?

It's bash to the rescue.

This script builds an index file of known themed functions, extracts your existing declared function and the theme_function from the original and your template file then uses 'diff' to show the difference in side-by-side format! awesome

This could be used to diff your existing functions in template.php with a freshly upgraded install to see how the new theme function differs from your existing template.php so you know what todo to make for a clean upgrade!

Check the attached file, dont forget to chmod +x the bash script and run it from within drupal's basedir

ie (the output is a lot tidier on your console!)

download the drupal bash script here