[clang] [emacs][clang-format] Add elisp API for clang-format on git diffs (PR #112792)

[Luke Lau via cfe-commits]

lukel97 wrote:

Just a heads up I've been using this locally for a bit now and it's been great, thanks for working on this. Haven't run into any issues so far.

https://github.com/llvm/llvm-project/pull/112792