Add Ability to List All Branches From External Repo

[awhisler]

I have a use case where we are running a pipeline that runs QA testing automation but sometimes, based on new requirements, I want the ref to change if there is an existing branch out there with the same name as the current repo

Workflow goes as follow:

1. On PR on a front end framework, the github action is triggered and it checks out an external repo, clones it, and brings it to this repo
2. But whenever I need to make a change on the automation to accommodate new requirements, I add a branch with the same name as the front end repo
3. So what I want to be able to do is list all the branches in this remote repo so that I can say 'if one of these branches matches the current branch, use that branch as the ref' and if not, just use main

I saw there was a fetch-depth property but looking at the documentation, I don't exactly see how I can list this history or access the list