How do you do the nice line-by-line (or section-by-section) before/after handling in a CLI tool?

Start with a clean git (even if you're just committing WIP locally). Run the tool. See the diffs in your IDE. They show up immediately in IntelliJ; use the "commit" pane. Same as if I had edited a bunch of files.

Works fine.

It has an external editor option (which I havent tried) the cli interface by default is pretty bad for medium to large code changes.