Enforce Unix line endings for Clang/LLVM/MLIR projects

[jurahul]

Change top-level and LLVM/MLIR/Clang .clang-format files to enforce Unix line ending.

[jurahul]

This is a follow on to the coding standard change and the discussion on https://discourse.llvm.org/t/llvm-source-file-line-endings/81388/16.

With this, folks attempting to commit C/C++ files with non-unix line endings will see a clang-format failure in GitHub CI. Currently enabling it for just clang/llvm/mlir projects, but if this seems reasonable and sticks, we can potentially incorporate it into the LLVM pre-defined style in clang-format.

[jurahul]

@bogner to see if this is ok for a folks using Windows predominantly.

[nikic]

LGTM, but someone working on Windows should confirm. This will be good for the CI checks, but I'm not sure if this will negatively affect people's local checkouts.

[jh7370]

Windows developer here, LGTM. I have most of my tree with \n line endings and haven't seen any negative impacts.

What happens to the files that specifically require \r\n endings for test purposes? Are these going to get mis-formatted/flagged as incorrect by clang-format?

[jurahul]

Thanks for confirming that Windows side is fine. I assume clang-format runs only on C/C++ source files, so other files like .bat or .py should be unaffected by this change. Additionally, in my test PR #161257 I had modified a .cpp file under llvm/test and it did not complain, because llvm/test/.clang-format has DisableFormat: true. The same is true for clang/test/.clang-format. mlir/test does not have a .clang-format as the .cpp/.h file in there are true source files that are built as a part of the build and are not test inputs.

[jh7370]

Thanks for confirming that Windows side is fine. I assume clang-format runs only on C/C++ source files, so other files like .bat or .py should be unaffected by this change. Additionally, in my test PR #161257 I had modified a .cpp file under llvm/test and it did not complain, because llvm/test/.clang-format has DisableFormat: true. The same is true for clang/test/.clang-format. mlir/test does not have a .clang-format as the .cpp/.h file in there are true source files that are built as a part of the build and are not test inputs.

Thanks, sounds good to me.