Support --fix argument on changed lines

[ilaner]

When executing riff with --fix flag, it will fix the code in all lines and not only on changed lines.
Basically we can revert ruff changes (using git) on all unchanged lines.

[dorschw]

Interesting idea, thanks

Could be challenging as I'm not certain that fixes always replace one line with one line (e.g. there could be a fix that changes a line into more than one, or vice versa)