changelog-check.yml

name: Changelog Fragment Check

on:
  pull_request:
    branches: 
      - main
      - 'release/v**'
      - 'maint/**'

permissions:
  contents: read
  pull-requests: write

jobs:
  check-fragment:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
        with:
          fetch-depth: 0 # Ensure full history is fetched

      - name: Check for changelog fragment
        env:
          PR_TITLE: ${{ github.event.pull_request.title }}
          HEAD_REF: ${{ github.head_ref }}
        run: |
          # Fetch the base branch explicitly to ensure it's available for comparison
          git fetch origin ${{ github.base_ref }}

          # --- EXEMPTION FOR RELEASE BRANCH MERGES ---
          # Release branches already contain changelog fragments from development
          # Skip fragment check for PRs from release/* branches to main
          if [[ "$HEAD_REF" =~ ^release/ ]]; then
            echo "✓ Release branch PR, fragment check skipped (fragments already in branch history)"
            exit 0
          fi
          # --- END RELEASE BRANCH EXEMPTION ---

          # Compare the head of the PR (current HEAD) with the base branch's remote tracking ref
          # This compares the changes introduced by the PR branch relative to its base.
          # Use --diff-filter=A to only consider added files for fragment check
          CHANGED_FILES=$(git diff --name-only --diff-filter=A origin/${{ github.base_ref }}...HEAD)

          # Debugging: Print the diff command and its output
          echo "Executing: git diff --name-only --diff-filter=A origin/${{ github.base_ref }}...HEAD"
          echo "Changed files (added only): $CHANGED_FILES"

          # --- EXEMPTION FOR CHANGELOG BUILD PRS ---
          # Check if PR title indicates a changelog update (e.g., "docs: update CHANGELOG")
          # This exempts PRs that are specifically for building the changelog (which remove fragments)
          if [[ "$PR_TITLE" =~ ^docs:\ update\ CHANGELOG ]]; then
            echo "✓ PR title indicates changelog update, fragment check skipped"
            exit 0
          fi
          # --- END EXEMPTION ---
          
          # Check if any changelog fragment was added
          if echo "$CHANGED_FILES" | grep -q "^changelog.d/[0-9].*\.md$"; then
            echo "✓ Changelog fragment found"
            exit 0
          fi
          
          # Check if this is an internal change (exempt from fragment requirement)
          if echo "$CHANGED_FILES" | grep -qE "^(tests/|docs/|\.github/)"; then
            echo "✓ Internal change, fragment not required"
            exit 0
          fi
          
          # Check if PR is marked as trivial
          if [[ "$PR_TITLE" =~ \[trivial\] ]]; then
            echo "✓ PR marked as trivial, fragment not required"
            exit 0
          fi
          
          echo "✗ Missing changelog fragment"
          echo "Please add a changelog fragment in changelog.d/"
          echo "Example: changelog.d/${{ github.event.number }}.fixed.md"
          echo ""
          echo "Fragment types:"
          echo "  - added.md      - New features"
          echo "  - fixed.md      - Bug fixes"
          echo "  - changed.md    - Behavior changes"
          echo "  - deprecated.md - Deprecations"
          echo "  - removed.md    - Removed features"
          echo "  - security.md   - Security fixes"
          echo ""
          echo "If this PR does not need a changelog entry, add [trivial] to the title."
          exit 1