_classic-buildpack-prepare-release.yml

name: _classic-buildpack-prepare-release

on:
  workflow_call:
    inputs:
      custom_update_command:
        description: An additional command to run before changes are committed, which can make use of the env vars EXISTING_VERSION and NEW_VERSION.
        type: string
        required: false

defaults:
  run:
    # Setting an explicit bash shell ensures GitHub Actions enables pipefail mode too,
    # rather than only error on exit (improving failure UX when pipes are used). See:
    # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsshell
    shell: bash

jobs:
  prepare-release:
    name: Prepare Release
    runs-on: pub-hk-ubuntu-24.04-ip
    steps:
      # We use our GitHub App's access token instead of GITHUB_TOKEN since otherwise other
      # workflows (such as CI) won't automatically run on any PRs opened by this workflow:
      # https://docs.github.com/en/actions/using-workflows/triggering-a-workflow#triggering-a-workflow-from-a-workflow
      - name: Generate access token for Linguist GitHub App
        uses: actions/create-github-app-token@v1
        id: generate-token
        with:
          app-id: ${{ vars.LINGUIST_GH_APP_ID }}
          # Note: The calling workflow must enable secrets inheritance for this variable to be accessible:
          # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idsecretsinherit
          private-key: ${{ secrets.LINGUIST_GH_PRIVATE_KEY }}

      - name: Checkout
        uses: actions/checkout@v4
        with:
          # We always want the version bump/changelog and resultant PR to target main, not the branch of the workflow_dispatch.
          ref: main
          # Tags are not fetched by default, but we need them to determine the existing buildpack version.
          fetch-tags: true
          # Force a full clone, otherwise fetch-tags doesn't actually fetch any tags:
          # https://github.com/actions/checkout/issues/1471
          fetch-depth: 0
          token: ${{ steps.generate-token.outputs.token }}

      - name: Determine existing tagged version
        id: existing-version
        run: echo "version=$(git tag --list 'v*' --sort '-version:refname' | head --lines 1 | tr --delete 'v')" >> "${GITHUB_OUTPUT}"

      - name: Calculate new version
        id: new-version
        run: echo "version=$(( ${{ steps.existing-version.outputs.version }} + 1 ))" >> "${GITHUB_OUTPUT}"

      - name: Update changelog
        run: |
          EXISTING_VERSION='${{ steps.existing-version.outputs.version }}'
          NEW_VERSION='${{ steps.new-version.outputs.version }}'
          DATE_TODAY="$(date --utc --iso-8601)"
          UNRELEASED_URL="https://github.com/${{ github.repository }}/compare/v${NEW_VERSION}...main"
          NEW_VERSION_URL="https://github.com/${{ github.repository }}/compare/v${EXISTING_VERSION}...v${NEW_VERSION}"

          sed --in-place --regexp-extended \
            --expression "s~(^## \[Unreleased\])$~\1\n\n\n## [v${NEW_VERSION}] - ${DATE_TODAY}~" \
            --expression "s~(^\[unreleased\]:) .*$~\1 ${UNRELEASED_URL}\n[v${NEW_VERSION}]: ${NEW_VERSION_URL}~" \
            CHANGELOG.md

      - name: Run custom update command
        if: inputs.custom_update_command != ''
        run: ${{ inputs.custom_update_command }}
        env:
          EXISTING_VERSION: ${{ steps.existing-version.outputs.version }}
          NEW_VERSION: ${{ steps.new-version.outputs.version }}

      - name: Generate list of unreleased commits
        id: unreleased-commits
        # See https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#multiline-strings
        run: |
          {
            echo 'commits<<COMMITS_LIST_END'
            git log --topo-order --reverse --format='- %s' v${{ steps.existing-version.outputs.version }}...main
            echo COMMITS_LIST_END
          } >> "${GITHUB_OUTPUT}"

      - name: Create pull request
        id: pr
        uses: peter-evans/create-pull-request@v7.0.5
        with:
          token: ${{ steps.generate-token.outputs.token }}
          title: Prepare release v${{ steps.new-version.outputs.version }}
          body: |
            Commits since the last release:
            ${{ steps.unreleased-commits.outputs.commits }}

            For the full diff, see the compare view:
            https://github.com/${{ github.repository }}/compare/v${{ steps.existing-version.outputs.version }}...main
          commit-message: Prepare release v${{ steps.new-version.outputs.version }}
          branch: prepare-release
          delete-branch: true
          committer: ${{ vars.LINGUIST_GH_APP_USERNAME }} <${{ vars.LINGUIST_GH_APP_EMAIL }}>
          author: ${{ vars.LINGUIST_GH_APP_USERNAME }} <${{ vars.LINGUIST_GH_APP_EMAIL }}>
      - name: PR link for GitHub summary
        if: ${{ steps.pr.outputs.pull-request-number }}
        run: echo '## PR [#${{ steps.pr.outputs.pull-request-number }}](${{ steps.pr.outputs.pull-request-url }}) ${{ steps.pr.outputs.pull-request-operation }}' >> "$GITHUB_STEP_SUMMARY"

      - name: Enable pull request auto-merge
        if: steps.pr.outputs.pull-request-operation == 'created'
        run: gh pr merge --auto --squash "${{ steps.pr.outputs.pull-request-number }}"
        env:
          GH_TOKEN: ${{ steps.generate-token.outputs.token }}