Hi,

Currently --list-different only prints the filenames of files that aren't formatted. It would be great to add an option to print out a diff between current and formatted source.

Maybe an extra option like --list-different --diff that would affect the way --list-different works. I believe in any case --list-different runs formatter on the source code, so it shouldn't be too hard to run it through some diff tool and output a nicely colored code to console.