This repo es for demonstration purposes only. It only goes to show that you can add anyone to a repo as a collaborator, even without them having to know about it. You can find the details about this implementation in my blog post in Spanish here. In that article, you will be able to find out how to configure automatic signing of your commits in your machine.
Linus Torvalds is not a collaborator of this repo, but appears as such on the side bar.