Checkout folked branch but pull request's github.event.pull_request.base.sha is synced with origin repo's main branch, not folked repo's main branch.

[AllyW]

I checkout a test-branch from a folked repo of a repo, and then make a pull request to the original repo's main branch.

But pull request's github.event.pull_request.base.sha is shown as original repo's head commit of main branch, not folked repo's head commit of main branch (original main branch's head commit might have changed cause someone may have merged some code into it, so folked repo's main branch is behind the original repo main branch).

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[cory-miller]

This is working as intended (it also it not related to actions/checkout).

If you open a PR against the original repository, then the "base" is the original repository.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests
https://docs.github.com/en/webhooks/webhook-events-and-payloads#pull_request