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Commit data for GitHub Actions

How to get correct git commit information when using GitHub Actions
Running tests using GitHub Actions can generate confusing git information. For example, instead of the last commit message (or pull request title), one can see something like:
Merge de7282540ac30ee4e32a0b1fede4f6391b4cc321 into fa58941d8a807b83ec5a3e5bfb83418ce12173c7
Also, the branch name becomes refs/pull/12/merge instead of the expected branch name. Why is that happening?
That happens when your GitHub Actions workflow is triggered by pull_request.
It changes the behaviour of @actions/checkout - it creates a new merge commit, which is created from merging the base to the head.
  • it performs git checkout to github.ref environment variable
  • it sets the git ref to refs/remotes/pull/##/merge
  • it sets the commit SHA to an arbitrary value that is different from the commit that triggered the workflow
To change the default behaviour and checkout the triggering commit, use the following @actions/checkout configuration
- uses: actions/checkout@v2
ref: ${{ github.event.pull_request.head.sha }}
Read more about GitHub Actions and pull_request (by