[wyuenho]

I'm pretty sure you can already do that with some scripting. Just write a git alias, say git edit, which will run the work tree copy through your favorite formatter to a temp file and send that temp file to your editor, and a commit hook to rename all the temp files back to the original and format them back to whatever the canonical format is. You can also configure your git diff and stash etc to make them aware of the temp file naming convention. You might even be able to write a script to generate all these aliases. There are some annoying details such as needing a separate command to temporarily move the temp files to the work tree to give your IDE a hand, but totally doable. It's going to take maybe a few weeks of work, but doable for a single person.