Related: my favorite viewer is diff2html-cli which lets you see the diff in your browser:

https://diff2html.xyz/

I recently implemented a diff driver as part of git-dogs. The integration part Claude one-shotted. The actual diffing was a bit more work though.

Mine is token based: https://replicated.wiki/blog/img/difflet.png

The set of git tools itself, very much in development: https://github.com/gritzko/git-dogs