You can create a global gitignore in your home directory. I have ‘.<myname>’ ignored there, so if I ever create a directory with that name I know it’s contents won’t go into source control. That way I don’t have to edit the repositories gitignore with me-specific stuff.
You wouldn't have to edit the actual repositories gitignore anyways. Every checkout of a repo comes with a .git/info/exclude file, which acts like a local additional gitignore file.
