[clang-tools-extra] [clang] [llvm] Accept /branch: and /cherry-pick: commands (PR #80838)

[Shourya Goel via cfe-commits]

Sh0g0-1758 wrote:

I hope the number of commits can be overlooked. Ran into some rebasing issues. Added a PR summary for the merge commit. 

https://github.com/llvm/llvm-project/pull/80838