Diffoscope is a diff utility which recursively unpacks archives, ISOs, etc., transforming a wide variety of files into human-readable forms before comparison instead of simply showing the raw difference in hexadecimal.

I recently added a progress bar when diffoscope is run on a terminal:

https://i.imgur.com/LDe4FNS.gif

Note that as diffoscope can, at any point, encounter an archive or format that requires unpacking, the progress will always be approximate and may even appear to go "backwards".

The implementation, available in version 61, is simple (see #1, #2, #3 & #4) but takes into account of a number of subtleties by using context managers to correctly track the state throughout.