GitHub Actions: Expressions, Contexts, Variables, and Outputs

- run: echo "Ref is ${{ github.ref }}"

# Read metadata from the current workflow run.

env:
  APP_ENV: ${{ vars.APP_ENV }}

# Read configuration values from the `vars` context.

strategy:
  matrix: ${{ fromJson(needs.prepare.outputs.matrix) }}

# Convert JSON text into a matrix object.

if: contains(github.event.pull_request.labels.*.name, 'deploy-preview')

# Use `contains()` in workflow conditions.

echo "IMAGE_TAG=${GITHUB_SHA}" >> "$GITHUB_ENV"

# Append to `GITHUB_ENV` to persist a variable in the current job.

echo "version=1.2.3" >> "$GITHUB_OUTPUT"

# Append to `GITHUB_OUTPUT` to expose a named output.

- id: version
  run: echo "value=1.2.3" >> "$GITHUB_OUTPUT"

- run: echo "Version is ${{ steps.version.outputs.value }}"

# Use the `steps` context to consume a step output.

jobs:
  prepare:
    runs-on: ubuntu-latest
    outputs:
      version: ${{ steps.meta.outputs.version }}
    steps:
      - id: meta
        run: echo "version=1.2.3" >> "$GITHUB_OUTPUT"

  deploy:
    needs: prepare
    runs-on: ubuntu-latest
    steps:
      - run: echo "Deploying ${{ needs.prepare.outputs.version }}"

# Pass values between jobs through `needs`.

{
  echo 'notes<<EOF'
  cat CHANGELOG.md
  echo 'EOF'
} >> "$GITHUB_OUTPUT"

# Preserve newlines in an output variable.