When operating on a local clone of repo and not on the main branch, for example:

navigate to google-cloud-python and create a test branch, then run:

LIBRARIAN_GITHUB_TOKEN=$(gh auth token) librarian generate -api=google/cloud/hypercomputecluster/v1beta -library=google-cloud-hypercomputecluster -push

It's branch is ignored, and eventually raises a PR against main branch. see comment

I think the desired behavior should be creating PR against test branch, equivalent to providing -branch=test when letting Librarian fetch repo from remote.

To fix, we likely want to check the current branch if opening a repo from dir and set branch accordingly.

Or, alternatively if we don't want to support branches on local repo dirs, then we should document and add a check to fail early.