check_crlf.py

#!/usr/bin/env python3

import subprocess
import os
from typing import Iterable

def main() -> int:
    any_failed = False
    for file_name in get_text_files():
        if is_file_crlf(file_name):
            print(f"::error file={file_name},title=File contains CRLF line endings::The file '{file_name}' was committed with CRLF new lines. Please make sure your git client is configured correctly and you are not uploading files directly to GitHub via the web interface.")
            any_failed = True

    return 1 if any_failed else 0


def get_text_files() -> Iterable[str]:
    # https://stackoverflow.com/a/24350112/4678631
    process = subprocess.run(
        ["git", "grep", "--cached", "-Il", ""],
        check=True,
        encoding="utf-8",
        stdout=subprocess.PIPE)

    for x in process.stdout.splitlines():
        yield x.strip()

def is_file_crlf(path: str) -> bool:
    if '\\' in path:
        print(f"File {path} contains a backslash in its name.")
        return True

    with open(path, "rb") as f:
        for line in f:
            if line.endswith(b"\r\n"):
                return True

    return False

exit(main())