I have been dealing with a strange heisen-bug with my Zettelkasten notes where occasionally a note will wind up with the wrong (or mixed) line endings after it has been updated by a script that inserts backlinks within the notes. I say heisen-bug since I can’t reproduce it and I’m not 100% confident that it is the script that is triggering this problem.
The symptom of this problem is when the file is open in Emacs, you see ugly “^M” characters at the end of each-line. The easiest way to fix this is by running the following command:
M-x replace-string RET C-q C-m RET RET
Breaking it down, we are calling the replace-string function in Emacs and when prompted to enter the string to search for type C-q C-m. Typing C-q allows us to enter the literal ^M character. Finally, we hit RET when prompted for the replacement text and that should result in all the wrong line-endings being removed.
Tested with: Emacs 26.3 on Windows 10.