[clang] [clang-tools-extra] [llvm] [clang-format] Add support for BasedOnStyle referencing an arbitrary file (PR #107312)

[kadir çetinkaya via llvm-commits]

kadircet wrote:

I am not sure if it's best to push a new command line flag to all other tools that use clang-format as a library.

Have you considered any other alternatives that can self-contain this in clang-format? e.g can we just treat paths as relative to current `.clang-format` file ?

https://github.com/llvm/llvm-project/pull/107312