[clang] [clang-format] Use double hyphen for multiple-letter flags (PR #100978)

[via cfe-commits]

magic-akari wrote:

> You certainly can add the double hyphen flags, but you can't remove the single ones.

There seems to be a misunderstanding. Please review the original issue. 

I did _not_ eliminate support for single hyphens in clang-format. 

What I did was modify the scripts that call clang-format, including clang-format-diff.py, clang-format-sublime.py, clang-format.el, clang-format.py, and git-clang-format. 

I updated them to use the standard flag format as specified in the clang-format help. 

The clang-format tool itself remains unchanged and continues to accept single hyphens.

https://github.com/llvm/llvm-project/pull/100978