pr-commit-summary.yml

name: PR commit summary

on:
  pull_request:
    types: [opened, reopened, synchronize]

jobs:
  update-pr-body:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write

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

      - name: Collect commit list
        id: commits
        shell: bash
        run: |
          BASE_SHA="${{ github.event.pull_request.base.sha }}"
          HEAD_SHA="${{ github.event.pull_request.head.sha }}"

          git fetch --no-tags --prune origin "${{ github.event.pull_request.base.ref }}"

          commits="$(git log --pretty=format:'- %s' "${BASE_SHA}..${HEAD_SHA}")"

          if [ -z "$commits" ]; then
            commits="- No commits found for this pull request."
          fi

          printf '%s\n' "$commits" > /tmp/pr_commits.txt

      - name: Update PR body preserving checklist
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          REPO: ${{ github.repository }}
          PR_TITLE: ${{ github.event.pull_request.title }}
          HEAD_REF: ${{ github.event.pull_request.head.ref }}
        shell: python
        run: |
          import os
          import re
          import subprocess
          from pathlib import Path

          pr_number = os.environ['PR_NUMBER']
          repo = os.environ['REPO']
          pr_title = os.environ['PR_TITLE']
          head_ref = os.environ['HEAD_REF']

          body = subprocess.check_output(
              ['gh', 'api', f'repos/{repo}/pulls/{pr_number}', '--jq', '.body // ""'],
              text=True,
          ) or ''

          linked_task_start = '<!-- AUTO-LINKED-TASK:START -->'
          linked_task_end = '<!-- AUTO-LINKED-TASK:END -->'
          start_marker = '<!-- AUTO-COMMIT-SUMMARY:START -->'
          end_marker = '<!-- AUTO-COMMIT-SUMMARY:END -->'

          commit_lines = Path('/tmp/pr_commits.txt').read_text(encoding='utf-8').strip()
          summary_content = f"{commit_lines}"

          task_match = re.search(
              r'(?im)^\s*(?:closes|fixes|resolves)\s+#(\d+)\b',
              body,
          )
          if task_match is None:
              task_match = re.search(r'(?<!\w)#(\d+)\b', pr_title)
          if task_match is None:
              task_match = re.match(r'(\d+)(?:[-_/]|$)', head_ref)
          if task_match is None:
              task_match = re.search(r'(?<!\w)#(\d+)\b', commit_lines)

          linked_task_content = ''
          if task_match is not None:
              linked_task_content = f'Closes #{task_match.group(1)}'

          marker_pattern = re.compile(
              rf'{re.escape(start_marker)}.*?{re.escape(end_marker)}',
              flags=re.S,
          )

          replacement = f"{start_marker}\n{summary_content}\n{end_marker}"

          if marker_pattern.search(body):
              # Markers already present (e.g. from the PR template): fill in place.
              updated = marker_pattern.sub(lambda _match: replacement, body)
          else:
              # No markers found: fall back to appending the block at the end.
              cleaned = body.rstrip()
              updated = cleaned + '\n\n' + replacement + '\n' if cleaned else replacement + '\n'

          linked_task_pattern = re.compile(
              rf'{re.escape(linked_task_start)}.*?{re.escape(linked_task_end)}',
              flags=re.S,
          )
          linked_task_replacement = (
              f'{linked_task_start}\n{linked_task_content}\n{linked_task_end}'
          )

          if linked_task_pattern.search(updated):
              updated = linked_task_pattern.sub(
                lambda _match: linked_task_replacement,
                updated,
              )

          subprocess.run(
              [
                  'gh', 'api',
                  f'repos/{repo}/pulls/{pr_number}',
                  '--method', 'PATCH',
                  '--field', f'body={updated}',
              ],
              check=True,
          )

          print('PR description updated with commit summary.')