GitHub Actions Cheatsheet: Workflows, Jobs and Matrix Reference

# .github/workflows/ci.yml — typical PR + push workflow
name: CI

on:
  push:
    branches: [main]
  pull_request:
    paths-ignore: ["docs/**", "**/*.md"]

permissions: { contents: read }

concurrency:
  group: ci-${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: ${{ github.event_name == 'pull_request' }}

jobs:
  test:
    runs-on: ubuntu-latest
    timeout-minutes: 15
    strategy:
      fail-fast: false
      matrix:
        python: ["3.11", "3.12", "3.13"]

    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: ${{ matrix.python }}
          cache: pip
      - run: pip install -r requirements.txt
      - run: pytest -q --cov=src --cov-report=xml
      - uses: codecov/codecov-action@v4
        if: success()
        with:
          file: coverage.xml

# .github/workflows/deploy.yml — tag-driven deploy with OIDC + environments
name: Deploy

on:
  push:
    tags: ["v*.*.*"]

permissions:
  id-token: write          # required for OIDC -> AWS / GCP
  contents: read

jobs:
  release:
    runs-on: ubuntu-latest
    environment:
      name: production     # requires manual approval if env is gated
      url: https://api.example.com

    steps:
      - uses: actions/checkout@v4

      - uses: aws-actions/configure-aws-credentials@v4
        with:
          role-to-assume: arn:aws:iam::123:role/gha-deploy
          aws-region:     us-east-1

      - name: Build + push image
        run: |
          docker build -t $IMAGE:$GITHUB_REF_NAME .
          docker push $IMAGE:$GITHUB_REF_NAME

      - name: Deploy
        run: ./scripts/deploy.sh $GITHUB_REF_NAME
        env:
          IMAGE: 123.dkr.ecr.us-east-1.amazonaws.com/app

# .github/workflows/_test.yml — reusable: callable from other workflows
name: Test (reusable)

on:
  workflow_call:
    inputs:
      python:
        type: string
        default: "3.12"
    secrets:
      CODECOV_TOKEN:
        required: false
    outputs:
      coverage:
        description: "Coverage percent"
        value: ${{ jobs.test.outputs.cov }}

jobs:
  test:
    runs-on: ubuntu-latest
    outputs:
      cov: ${{ steps.cov.outputs.value }}
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with: { python-version: ${{ inputs.python }} }
      - run: pip install -r requirements.txt
      - run: pytest --cov=src
      - id: cov
        run: echo "value=$(coverage report --format=total)" >> "$GITHUB_OUTPUT"

# Caller: .github/workflows/ci.yml
# jobs:
#   tests:
#     uses: ./.github/workflows/_test.yml
#     with: { python: "3.13" }
#     secrets: inherit

# .github/workflows/release.yml — lint -> test -> build -> publish, in one file.
name: Release

on:
  push:
    branches: [main]
    tags:     ["v*.*.*"]

permissions:
  contents: read
  packages: write          # to push to GHCR

concurrency:
  group: release-${{ github.ref }}
  cancel-in-progress: false

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with: { python-version: "3.13", cache: pip }
      - run: pip install ruff && ruff check .

  test:
    needs: lint
    uses: ./.github/workflows/_test.yml
    with: { python: "3.13" }
    secrets: inherit

  build:
    needs: test
    if: startsWith(github.ref, 'refs/tags/v')
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: docker/setup-buildx-action@v3
      - uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - uses: docker/build-push-action@v6
        with:
          push: true
          tags: ghcr.io/${{ github.repository }}:${{ github.ref_name }}
          cache-from: type=gha
          cache-to:   type=gha,mode=max