Hi,
Running mix format on larger projects can be slow since it checks every file. I don't think there is currently a way to run it on changed files only. Users could run `mix format $(git diff --name-only)` to achieve that but I am wondering whether it might be worth also adding this as a flag directly to mix format.
I am not sure how this would be implemented. Since the elixir compiler only compiles changed files maybe we could leverage the same code?
I would be happy to take a look at this if this proposal is accepted.
Best regards,
Dario