file-contents-sorter changes all newlines to unix-style '\n'

[Maetveis]

The file-contents-sorter hook replaces all windows-style newlines '\r\n' with linefeed '\n'.

This is especially confusing when using the hook in a git repository with core.autocrlf activated (the default in git for windows, and also used by windows GitHub runners). In this case the hook always fails (and replaces the newlines), but git shows no diff at all, due to line normalization.
This particular case can be worked around by setting gitattributes, but IMO the hook shouldn't be modifying line separators (mixed-line-ending can be used for that).