Discover and report which repository branch corresponds to github.repository's github.sha.
This is necessary for a release action because release actions are driven by a tag, which means that github.ref_name reports the tag rather than the corresponding branch.
| Input | Description |
|---|---|
| token | GitHub Personal Access Token with which to query the REST API |
| Output | Description |
|---|---|
| branch | name of the branch whose tip is github.sha, or empty string |
| relnotes | for a tag build, if the branch has a Pull Request, the release notes from the PR description |