swinton/README.md

## README.md

      
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    Verified commits made easy with GitHub Actions


So you want to commit changes generated by a GitHub Actions workflow back to your repo, and have that commit signed automatically?
Here's one way this is possible, using the REST API, the auto-generated GITHUB_TOKEN, and the GitHub CLI, gh, which is pre-installed on GitHub's hosted Actions runners.
You don't have to configure the git client, just add a step like the one below... Be sure to edit FILE_TO_COMMIT and DESTINATION_BRANCH to suit your needs.
    # Use the REST API to commit changes, so we get automatic commit signing
    - name: Commit changes
      env:
        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        FILE_TO_COMMIT: data.csv
        DESTINATION_BRANCH: data
      run: |
        export TODAY=$( date -u '+%Y-%m-%d' )
        export MESSAGE="chore: regenerate $FILE_TO_COMMIT for $TODAY"
        export SHA=$( git rev-parse $DESTINATION_BRANCH:$FILE_TO_COMMIT )
        export CONTENT=$( base64 -i $FILE_TO_COMMIT )
        gh api --method PUT /repos/:owner/:repo/contents/$FILE_TO_COMMIT \
          --field message="$MESSAGE" \
          --field content="$CONTENT" \
          --field encoding="base64" \
          --field branch="$DESTINATION_BRANCH" \
          --field sha="$SHA"
Caveats

Because of the underlying REST API, only 1 file can be committed at a time.
Notes

This is made possible because GitHub automatically signs commits from bots over the REST API. Since the GITHUB_TOKEN is a bot token, this also applies to commits from GitHub Actions.
See this blog post from 2019 for more details: https://github.blog/2019-08-15-commit-signing-support-for-bots-and-other-github-apps/