GitHub Actions Env & Commits

Environment

There are several ways to consume environment variables in GitHub Actions but I was unsure how to set environment variables. I have a Go build that uses -ldflags "-X main.OSVersion=${VERSION} -X main.GitCommit=${COMMIT}" to set variables in the binary that can be e.g. exported via Prometheus.

The GitCommit is straightforward as it’s one of GitHub Actions’ provided values and is just ${{ github.sha }}.

I wanted to set Version to be the value of uname --kernel-release. Since the build is using ubuntu-latest, this is easy to get but, how to set?

The solution is to use a run step:

- name: Get kernel version
  run: echo "VERSION=$(uname --kernel-release)" >> ${GITHUB_ENV}

NOTE The variable (VERSION) is set but then appended to ${GITHUB_ENV}

Then, in a following step, I can reference it as ${{ env.VERSION }}:

- name: build-push
  uses: docker/build-push-action@v2
  with:
    context: .
    file: ./Dockerfile
    build-args: |
    VERSION=${{ env.VERSION }}
    COMMIT=${{ github.sha }}
    tags: ghcr.io/${{ env.REPO }}:${{ github.sha }}
    push: true

Commits

It was non-obvious to me to understand how to commit changes made to the repo’s files during the GitHub Actions workflow. After reviewing several different posts, the following (amalgam) works:

- name: revise occurrences of the image
  run: |
    git config --local user.email "[email protected]"
    git config --local user.name "GitHub Actions"

    OLD="ghcr.io/${{ env.REPO }}:[0-9a-f]\{40\}"
    NEW="ghcr.io/${{ env.REPO }}:${{ github.sha }}"
    sed \
    --in-place \
    "s|${OLD}|${NEW}|g" \
    ./kubernetes.yaml
    git add ./kubernetes.yaml

    git commit --message "GitHub Actions update image references"
    git push origin master

That’s all!

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• GitHub Actions