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

[Campbell Barton via cfe-commits]

https://github.com/ideasman42 commented:

Works well on Linux, generally seems fine although I still think it's worth considering splitting out "getting-changes" into a separate shared code-base to avoid dealing with details of calling diff for different version control system here.

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