check-release-notes.yml

# A check that runs on release-please PRs that checks the `release-notes.md` 
# file to make sure it exists and that it's contents are different from the 
# previous release.

# Outcomes:
#  - Makes sure that we don't forget to update `release-notes.md` before 
#    published a release
  
# Steps:
# - Looks at the contents of `release-notes.md` from the last tag, and fails 
#   if the contents have not changed in a commit since

name: Check Release Notes

on:
  pull_request:
    types: [opened, synchronize]
    branches:
      - main

permissions:
  contents: read

jobs:
  check-release-notes:
    runs-on: ubuntu-latest
    if: |
      github.event.pull_request.head.ref == 'release-please--branches--main' &&
      startsWith(github.event.pull_request.title, 'chore(main): release')

    steps:
      - name: Checkout the PR
        uses: actions/checkout@v4
        with:
          ref: ${{ github.event.pull_request.base.ref }}
          fetch-depth: 0

      - name: Fetch all tags and branches
        run: git fetch --all --tags

      - name: Find previous release tag
        id: previous_release
        run: |
          previous_tag=$(git describe --tags `git rev-list --tags --max-count=1`)
          echo "previous_tag=$previous_tag" >> $GITHUB_ENV

      - name: Diff release-notes.md
        id: check_release_notes
        run: |
          if [ ! -f release-notes.md ]; then
            echo "release-notes.md file does not exist. Failing the workflow."
            exit 1
          fi

          previous_tag=${{ env.previous_tag }}
          if ! git diff $previous_tag HEAD --name-only | grep -q "^release-notes.md$"; then
            echo "release-notes.md file was not updated since the previous release. Failing the workflow."
            exit 1
          fi

          echo "release-notes.md file has been updated since the previous release. Well done!"