Please add an option to exclude file lists differences

This bug was originally reported by Mike Hommey (mh+reportbug@glandium.org) in Debian bug #879010:

It's usually more convenient to give tarballs than to extract them and
pass directories to diffoscope. But then the difference between the two
containers are displayed, while one might not care about those
differences. It might actually be true with directories too, where
differences about file stats might be shown that are otherwise unwanted.

I tried --exclude "file list" as suggested on irc, but that didn't work.

An option that allows to ignore at least the first-level of file lists
would be useful.