[clang] [clang][NFC] Trim license header comments to 81 characters (PR #82919)

[Balazs Benics via cfe-commits]

steakhal wrote:

I did some grepping.
Inside the `clang` project:
`^/+=(.*)/(.*)...$`: 297 files
`^/+=([^\n/]*)\.(h|cpp)([^\n/]*)...$`: 1766 files

This suggests to me that indeed, absolute paths are the used way fewer times.

https://github.com/llvm/llvm-project/pull/82919