I have this two liner as part of my post-os-install setup script:

    curl -fsSL https://www.toptal.com/developers/gitignore/api/linux > ~/.gitignore
    git config --global core.excludesFile ~/.gitignore

Assuming your global config is ~/.config/git/config, you can download it to ~/.config/git/ignore and not need the overriding explicit excludesFile.