This repository shows how to use commitlint in a GitHub Action to check commit-messages of commits in pull-requests.
See the commitlint.yml for the complete workflow.
Check in the Action tab or the closed pull requests to see the status (successful/failed) of the actions.
The straight-forward solution is to use the --to and --from arguments of commitlint with the SHA-1 values instead of the branch names or relative references. On the one hand, this reliably solves the problem of unknown revisions or paths in the working tree. On the other hand, only commits in scope of the PR will be checked. As a sidenote: GitHub uses the same references (SHA-1) for the ad-hoc merge that is being checked-out.
We need the base-SHA as well as the head-SHA. In a GitHub action those values are available in the pull-request object of the event in the github-context.
The the actual linting can be done with the following command:
npx commitlint --from ${{ github.event.pull_request.base.sha }} --to ${{ github.event.pull_request.head.sha }} --verbose