Renaming a branch in GitHub

I just renamed my local branch using

git branch -m oldname newname

but this only renames the local version of the branch. How can I rename the one on GitHub?

Branch Rename is now available through GitHub API

You can rename a branch with the GitHub REST API.

And you can easily run API commands via the gh CLI all like this:

gh api "repos/{owner}/{repo}/branches/{branch}/rename" -f new_name={newBranch}