`create_pull_request` doesn't check out branch when called from `pull_request` event

[georeith]

Describe the bug
create_pull_request does not check out the correct branch when called from an action triggered by pull_request events, this means it runs on your main branch and attempts to PR any changes on main that aren't on your PR too.

The issue is that GITHUB_REF doesn't refer to the branch name on an action triggered via pull_request event it looks like: refs/pull/{pr_number}/merge.

github-action/entrypoint.sh

Line 233 in 6ed209d

git checkout "${GITHUB_REF#refs/heads/}"

It should instead use ${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}.

source