release.yml

# This workflow automatically creates a draft release with the same title and body as the release PR
# as soon as that PR is merged into `main`.
name: Release

# Only execute when a release branch has been merged into "main".
on:
  pull_request:
    types:
      - closed
    branches:
      - main

jobs:

  # Automatically prepare a draft release following a successful merge into `main`.
  prepare-release:
    if: github.event.pull_request.merged == true
    name: Prepare release
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2

      - name: Determine the release version
        id: parse-version
        env:
          # This looks scary, but it's a PCRE regular expression that parses the version number
          # from a branch name based on semver.
          #
          # Reference and examples of matched patterns: https://regexr.com/6jfqu
          pattern: '(?:^|\/)v?\.?\K(\d+\.\d+\.\d+(-[0-9A-Za-z-]+(?:\.\d+)?)?(\+(?:\.?[0-9A-Za-z-]+)+)?)$'
        run: |
          version=$(grep -oP "${{ env.pattern }}" <<< "${{ github.event.pull_request.head.ref }}")
          echo "::set-output name=version::$version"
          echo "Parsed version: '${version}'"

      - name: Publish the draft release
        id: publish
        uses: ncipollo/release-action@v1
        with:
          token: ${{ secrets.GITHUB_TOKEN }}
          tag: "v${{ steps.parse-version.outputs.version }}"
          name: ${{ github.event.pull_request.title }}
          body: ${{ github.event.pull_request.body }}
          draft: true

      - name: Release details
        run: |
          echo "Draft release has been published: ${{ steps.publish.outputs.html_url }}"