backport.yml

name: Backport

on:
  pull_request_target:
    types: ["labeled", "closed"]

permissions:
  contents: write
  pull-requests: write

jobs:
  backport:
    name: Backport PR
    runs-on: ubuntu-latest
    # Only run for merged PRs that are not themselves backports (avoid loops).
    if: |
      github.event.pull_request.merged == true &&
      !(contains(github.event.pull_request.labels.*.name, 'backport'))
    steps:
      - name: Check for version labels
        id: check-labels
        env:
          LABELS: ${{ join(github.event.pull_request.labels.*.name, ' ') }}
        run: |
          for label in $LABELS; do
            if echo "$label" | grep -qE '^v[0-9]+\.[0-9]+\.[0-9]+'; then
              echo "Found version label: $label"
              echo "has_version_label=true" >> "$GITHUB_OUTPUT"
              exit 0
            fi
          done
          echo "No version label matching vN.N.N found — nothing to backport."
          echo "has_version_label=false" >> "$GITHUB_OUTPUT"

      - name: Backport Action
        id: backport
        if: steps.check-labels.outputs.has_version_label == 'true'
        uses: sorenlouv/backport-github-action@v10.2.0
        continue-on-error: true
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}

      - name: Info log
        if: steps.backport.outcome == 'success'
        run: cat ~/.backport/backport.info.log

      - name: Check for real failures
        if: steps.backport.outcome == 'failure'
        run: |
          cat ~/.backport/backport.debug.log
          if grep -q '"code":"no-branches-exception"' ~/.backport/backport.debug.log 2>/dev/null; then
            echo "No target branches matched the version labels — nothing to backport. This is OK."
            exit 0
          fi
          echo "::error::Backport failed with a real error"
          exit 1

      - name: Enable auto-merge on backport PRs
        if: >-
          steps.backport.outcome == 'success' &&
          contains(github.event.pull_request.labels.*.name, 'auto-backport')
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          REPO: ${{ github.repository }}
        run: |
          # Extract created PR numbers from the backport info log.
          PR_NUMBERS=$(grep -oE '"pullRequestNumber":[0-9]+' ~/.backport/backport.info.log \
            | grep -oE '[0-9]+' || true)
          if [ -z "$PR_NUMBERS" ]; then
            echo "No backport PRs found in log. Skipping auto-merge."
            exit 0
          fi
          for pr in $PR_NUMBERS; do
            echo "Enabling auto-merge (squash) on PR #$pr"
            gh pr merge "$pr" --repo "$REPO" --auto --squash || \
              echo "::warning::Could not enable auto-merge on #$pr (is auto-merge enabled in repo settings?)"
          done

  remove-backport-pending:
    name: Remove backport-pending label
    runs-on: ubuntu-latest
    # Run when a backport PR is merged or closed.
    if: |
      github.event.pull_request.merged == true &&
      contains(github.event.pull_request.labels.*.name, 'backport')
    steps:
      - name: Check if all backports are complete
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          PR_TITLE: ${{ github.event.pull_request.title }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          REPO: ${{ github.repository }}
        run: |
          # Backport PR titles follow the pattern: [9.2] Original title (#1234)
          ORIGINAL_PR=$(echo "$PR_TITLE" | grep -oE '\(#[0-9]+\)' | tail -1 | tr -d '(#)')
          if [ -z "$ORIGINAL_PR" ]; then
            echo "Could not extract original PR number from title: $PR_TITLE"
            exit 0
          fi
          echo "Original PR: #$ORIGINAL_PR"
          echo "Just-merged backport PR: #$PR_NUMBER"

          HAS_LABEL=$(gh pr view "$ORIGINAL_PR" --repo "$REPO" --json labels \
            --jq '[.labels[].name] | if index("backport-pending") then "true" else "false" end')
          if [ "$HAS_LABEL" != "true" ]; then
            echo "Original PR #$ORIGINAL_PR does not have backport-pending label. Nothing to do."
            exit 0
          fi

          # Count open backport PRs, excluding the just-merged PR (API eventual consistency).
          OPEN_BACKPORTS=$(gh pr list --repo "$REPO" --label backport --state open \
            --json number,title \
            --jq "[.[] | select(.number != ${PR_NUMBER}) | select(.title | test(\"\\\\(#${ORIGINAL_PR}\\\\)\"))] | length")
          echo "Open backport PRs remaining: $OPEN_BACKPORTS"

          if [ "$OPEN_BACKPORTS" -eq 0 ]; then
            echo "All backport PRs are merged/closed. Removing backport-pending label from #$ORIGINAL_PR."
            gh pr edit "$ORIGINAL_PR" --repo "$REPO" --remove-label "backport-pending"
          else
            echo "Still $OPEN_BACKPORTS open backport PR(s). Keeping backport-pending label on #$ORIGINAL_PR."
          fi