Comment by FrenchyJiby

Yes-anding this to say:

For per-user gitignore, one can set the following config in ~/.gitconfig:

    # System-wide gitignore file
    # To avoid in-repo repetition for system-specifc garbage files
    [core]
        excludesfile = ~/.config/git/gitignore

Then your file at ~/.config/git/gitignore can be a normal format, and not need to be stored in repo. Perfect for system files (.DS_Store...) or editor swap files etc.