Create PR for Sibling Repository

Sometimes we want to create a GitHub PR for some repository besides upstream. The steps to follow are obscure, so this page describes how to do it.

Go to the Pull Requests page for the repository you wish to target, for example leandrolanzieri.

Click New Pull Request. Thee are buttons at the top to select the base repository and branch, as well as the head repository and branch. The logical approach is to change the base repository. However, the base we want, in our case leandrolanzieri, is not available.

Instead, click on the link switching the base in the text below the buttons. The resulting page now selects the repository we want, in this case leandrolanzieri/RIOT, as the base repository.

Now we can select the appropriate base branch, and head repository (kb2ma/RIOT) and branch.