auto-sync-prs.yml

name: Auto-Sync PR Branches
on:
  push:
    branches: [main]
  workflow_dispatch:

permissions:
  contents: write
  pull-requests: write

jobs:
  sync:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v7
        with:
          fetch-depth: 0

      - name: List open PRs targeting main
        id: prs
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          gh api repos/${{ github.repository }}/pulls \
            --jq '[.[] | select(.base.ref == "main" and .state == "open") | {number, headRef: .head.ref, headRepo: .head.repo.full_name, mergeable: .mergeable}]' \
            > open_prs.json
          echo "count=$(jq length open_prs.json)" >> $GITHUB_OUTPUT
          echo "Found $(jq length open_prs.json) open PR(s)"

      - name: Merge main into each same-repo PR
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          COUNT=$(jq length open_prs.json)
          for i in $(seq 0 $((COUNT - 1))); do
            PR=$(jq ".[$i]" open_prs.json)
            NUM=$(echo "$PR" | jq -r '.number')
            HEAD_REF=$(echo "$PR" | jq -r '.headRef')
            HEAD_REPO=$(echo "$PR" | jq -r '.headRepo')
            MERGEABLE=$(echo "$PR" | jq -r '.mergeable')

            echo "--- PR #$NUM ($HEAD_REF) ---"

            # Skip fork PRs (cannot push to fork branches)
            if [ "$HEAD_REPO" != "${{ github.repository }}" ]; then
              echo "  SKIP: fork PR — cannot push to $HEAD_REPO"
              continue
            fi

            # Skip conflicting PRs
            if [ "$MERGEABLE" = "CONFLICTING" ]; then
              echo "  SKIP: has merge conflicts"
              gh pr comment "$NUM" --repo ${{ github.repository }} \
                --body "⚠️ **Auto-sync skipped** — this PR has merge conflicts with main. Please resolve them manually."
              continue
            fi

            # Attempt merge
            git fetch origin "$HEAD_REF"
            if git checkout "$HEAD_REF" 2>/dev/null; then
              if git merge origin/main --no-edit 2>&1; then
                git push origin "HEAD:$HEAD_REF"
                echo "  ✅ Merged main into #$NUM"
              else
                git merge --abort 2>/dev/null
                echo "  ❌ Merge failed for #$NUM (may have conflicts now)"
                gh pr comment "$NUM" --repo ${{ github.repository }} \
                  --body "⚠️ **Auto-sync failed** — main could not be automatically merged into this branch. Please rebase manually."
              fi
            else
              echo "  ❌ Could not checkout $HEAD_REF"
            fi

            # Return to main for next iteration
            git checkout main 2>/dev/null
          done