backport-on-label.yml

name: Backport on Label
on:
  pull_request:
    types:
      - closed

jobs:
  detect:
    name: Detect backport labels
    runs-on: ubuntu-latest
    if: >-
      github.event.pull_request.merged == true &&
      contains(toJSON(github.event.pull_request.labels.*.name), 'backport-release-')
    outputs:
      branches: ${{ steps.detect.outputs.branches }}
    steps:
      - name: Extract target branches from labels
        id: detect
        env:
          LABELS_JSON: ${{ toJSON(github.event.pull_request.labels.*.name) }}
        run: |
          set -euo pipefail
          branches=()

          for label in $(echo "$LABELS_JSON" | jq -r '.[]'); do
            if [[ "$label" =~ ^backport-(release-[0-9]+\.[0-9]+)$ ]]; then
              branches+=("\"${BASH_REMATCH[1]}\"")
            fi
          done

          if [[ ${#branches[@]} -eq 0 ]]; then
            echo "branches=[]" >> "$GITHUB_OUTPUT"
          else
            echo "branches=[$(IFS=,; echo "${branches[*]}")]" >> "$GITHUB_OUTPUT"
          fi

  backport:
    name: Backport to ${{ matrix.target_branch }}
    needs: detect
    if: needs.detect.outputs.branches != '[]'
    permissions:
      contents: write
      pull-requests: write
    strategy:
      fail-fast: false
      matrix:
        target_branch: ${{ fromJSON(needs.detect.outputs.branches) }}
    uses: ./.github/workflows/backport.yml
    with:
      branch_name: ${{ matrix.target_branch }}
      pr_number: ${{ github.event.pull_request.number }}
    secrets: inherit