buzz/.github/workflows/sync-release-changelog.yml

name: Sync Release PR Changelog

on:
  push:
    branches: [main]

# Serialize successive main pushes — each run generates the correct changelog.
concurrency:
  group: sync-release-changelog
  cancel-in-progress: false

permissions:
  contents: write
  pull-requests: write

jobs:
  sync:
    name: Sync changelog on open release PR
    runs-on: ubuntu-latest
    steps:
      - name: Find open release PR
        id: find-pr
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          set -euo pipefail

          # Filter to same-repo PRs only (exclude forks) with version-bump/<semver> branches.
          PRS=$(gh pr list \
            --repo block/sprout \
            --state open \
            --base main \
            --limit 100 \
            --json number,headRefName,headRepository \
            --jq '[.[] |
              select(.headRepository.nameWithOwner == "block/sprout") |
              select(.headRefName | test("^version-bump/[0-9]+\\.[0-9]+\\.[0-9]+(-[0-9A-Za-z.-]+)?$"))
            ]')

          COUNT=$(echo "$PRS" | jq 'length')

          if [[ "$COUNT" -eq 0 ]]; then
            echo "No open release PR found — nothing to sync"
            echo "found=false" >> "$GITHUB_OUTPUT"
            exit 0
          fi

          if [[ "$COUNT" -gt 1 ]]; then
            echo "::error::Multiple open release PRs found — cannot auto-sync. Resolve manually."
            echo "$PRS" | jq -r '.[].headRefName'
            exit 1
          fi

          BRANCH=$(echo "$PRS" | jq -r '.[0].headRefName')
          NUMBER=$(echo "$PRS" | jq -r '.[0].number')
          VERSION="${BRANCH#version-bump/}"

          echo "found=true" >> "$GITHUB_OUTPUT"
          echo "branch=$BRANCH" >> "$GITHUB_OUTPUT"
          echo "number=$NUMBER" >> "$GITHUB_OUTPUT"
          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
          echo "Found release PR #${NUMBER} (${BRANCH})"

      - name: Generate GitHub App token
        if: steps.find-pr.outputs.found == 'true'
        id: app-token
        uses: actions/create-github-app-token@v3
        with:
          client-id: ${{ vars.RELEASE_APP_CLIENT_ID }}
          private-key: ${{ secrets.RELEASE_APP_PRIVATE_KEY }}

      - name: Check out release PR branch
        if: steps.find-pr.outputs.found == 'true'
        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
        with:
          ref: ${{ steps.find-pr.outputs.branch }}
          fetch-depth: 0
          fetch-tags: true
          token: ${{ steps.app-token.outputs.token }}

      - name: Regenerate changelog section
        if: steps.find-pr.outputs.found == 'true'
        env:
          VERSION: ${{ steps.find-pr.outputs.version }}
          PR_NUMBER: ${{ steps.find-pr.outputs.number }}
          GH_TOKEN: ${{ steps.app-token.outputs.token }}
        run: |
          set -euo pipefail

          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
          git config user.name "github-actions[bot]"

          # Refresh origin/main so the log range reflects what's actually on main now.
          git fetch origin main

          # Most recent release tag reachable from origin/main (i.e., the previous release).
          # Using origin/main — not HEAD — so the release commit on this PR branch is excluded.
          LAST_TAG=$(git describe --tags --abbrev=0 --match 'v[0-9]*' origin/main 2>/dev/null || echo "")

          if [[ -z "$LAST_TAG" ]]; then
            NEW_ENTRIES="Initial release"
          else
            # Entries since the last tag up to current main tip, excluding merge commits.
            # Upper bound is origin/main, NOT HEAD, so release/sync commits on this PR
            # branch never appear in the changelog.
            NEW_ENTRIES=$(git log "${LAST_TAG}..origin/main" --oneline --no-merges || echo "")
          fi

          echo "Changelog range: ${LAST_TAG:-<beginning>}..origin/main"
          echo "New entries:"
          echo "${NEW_ENTRIES:-  (none)}"

          # Locate the ## v<VERSION> section in CHANGELOG.md.
          START=$(grep -n "^## v${VERSION}$" CHANGELOG.md | head -1 | cut -d: -f1)
          if [[ -z "$START" ]]; then
            echo "::error::Section '## v${VERSION}' not found in CHANGELOG.md — cannot sync"
            exit 1
          fi

          # Line number of the next ## v section after our section (may be empty if last).
          NEXT=$(awk -v start="$START" 'NR > start && /^## v[0-9]/{print NR; exit}' CHANGELOG.md)

          TMPFILE=$(mktemp)

          # Lines before the version section (the "# Changelog" header block).
          if [[ "$START" -gt 1 ]]; then
            head -n $((START - 1)) CHANGELOG.md >> "$TMPFILE"
          fi

          # Write the refreshed version section.
          printf '## v%s\n\n' "$VERSION" >> "$TMPFILE"
          if [[ -n "$NEW_ENTRIES" ]]; then
            printf '%s\n' "$NEW_ENTRIES" >> "$TMPFILE"
          else
            printf 'No changes.\n' >> "$TMPFILE"
          fi
          printf '\n' >> "$TMPFILE"

          # Append the remainder of the changelog (previous releases).
          if [[ -n "$NEXT" ]]; then
            tail -n "+${NEXT}" CHANGELOG.md >> "$TMPFILE"
          fi

          mv "$TMPFILE" CHANGELOG.md

          # Skip commit if nothing changed.
          if git diff --quiet CHANGELOG.md; then
            echo "Changelog already up to date — nothing to commit"
            exit 0
          fi

          git add CHANGELOG.md
          git commit -m "chore(release): sync changelog for v${VERSION}"
          git push origin "HEAD:refs/heads/version-bump/${VERSION}"

          # Update the PR body with the refreshed commit list.
          if [[ -n "$LAST_TAG" ]]; then
            PR_HEADER="### Changes since ${LAST_TAG}:"$'\n\n'"${NEW_ENTRIES}"
          else
            PR_HEADER="Initial release."
          fi
          PR_BODY="## Release v${VERSION}"$'\n\n'"${PR_HEADER}"$'\n\n'"**To release:** merge this PR. The tag and build will happen automatically."

          gh pr edit "$PR_NUMBER" --body "$PR_BODY"
          echo "Changelog synced and PR #${PR_NUMBER} body updated"