backport.yml

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

jobs:
  collect-backport-targets:
    name: Collect Backport Targets
    runs-on: ubuntu-latest
    outputs:
      target_branches_json: ${{ steps.collect-targets.outputs.target_branches_json }}
    # Only react to merged PRs for security reasons.
    # See https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows#pull_request_target.
    if: >
      github.event.pull_request.merged
      && (
        (
          github.event.action == 'closed'
          && contains(join(github.event.pull_request.labels.*.name, ','), 'backport ')
        )
        || (
          github.event.action == 'labeled'
          && contains(github.event.label.name, 'backport ')
        )
      )
    steps:
      - name: Collect Backport Labels (Labeled Event)
        if: github.event.action == 'labeled'
        env:
          BACKPORT_LABEL: ${{ github.event.label.name }}
        run: |
          rm -f /tmp/backport-labels.sorted.txt
          if echo "${BACKPORT_LABEL}" | grep -Eq '^backport [0-9]+\.[0-9]+$'; then
            echo "${BACKPORT_LABEL}" > /tmp/backport-labels.sorted.txt
          else
            echo "Label '${BACKPORT_LABEL}' does not match expected format 'backport x.y'."
            exit 1
          fi

      - name: Collect Backport Labels (Closed Event)
        if: github.event.action == 'closed'
        run: |
          rm -f /tmp/backport-labels.sorted.txt
          jq -r '.pull_request.labels[].name | select(test("^backport [0-9]+\\.[0-9]+$"))' "${GITHUB_EVENT_PATH}" \
            | sort -u \
            > /tmp/backport-labels.sorted.txt
          if [ ! -s /tmp/backport-labels.sorted.txt ]; then
            echo "No backport labels found for this merged PR."
            exit 1
          fi

      - name: Collect Target Branches
        id: collect-targets
        run: |
          TARGET_BRANCHES_JSON=$(awk '{ print $NF }' /tmp/backport-labels.sorted.txt | jq -R -s -c 'split("\n") | map(select(length > 0))')
          echo "target_branches_json=${TARGET_BRANCHES_JSON}" >> "$GITHUB_OUTPUT"

  backport:
    name: Backport (${{ matrix.target_branch }})
    needs: collect-backport-targets
    if: needs.collect-backport-targets.outputs.target_branches_json != '' && needs.collect-backport-targets.outputs.target_branches_json != '[]'
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false
      matrix:
        target_branch: ${{ fromJSON(needs.collect-backport-targets.outputs.target_branches_json || '[]') }}
    permissions:
      contents: write
      id-token: write
    steps:
      - uses: DataDog/dd-octo-sts-action@96a25462dbcb10ebf0bfd6e2ccc917d2ab235b9a # v1.0.4
        id: octo-sts
        with:
          scope: DataDog/dd-trace-py
          policy: self.backport.create-pr

      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
        with:
          persist-credentials: false
          fetch-depth: 0

      - name: Execute Backport
        id: create-commit
        env:
          TARGET_BRANCH: ${{ matrix.target_branch }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
        run: |
          git config --global user.name "${GITHUB_ACTOR}"
          git config --global user.email "${GITHUB_ACTOR}@users.noreply.github.com"

          MERGE_COMMIT=$(git rev-parse HEAD)
          WORKTREE=".worktrees/backport-${TARGET_BRANCH}"
          BACKPORT_BRANCH="backport-${PR_NUMBER}-to-${TARGET_BRANCH}"

          echo "Backporting ${MERGE_COMMIT} to ${TARGET_BRANCH}"
          git worktree add ${WORKTREE} ${TARGET_BRANCH}
          cd ${WORKTREE}
          git branch -D ${BACKPORT_BRANCH} || true
          git switch --create ${BACKPORT_BRANCH}

          echo "Cherrypicking"
          set +e
          CHERRYPICK_OUT=$(git cherry-pick -x --mainline 1 ${MERGE_COMMIT} 2>&1)
          CHERRYPICK_STATUS=$?
          set -e
          echo "Cherrypicking complete"
          echo "${CHERRYPICK_STATUS}"
          if [ "${CHERRYPICK_STATUS}" -ne 0 ]; then
            echo "Cherry-pick failed for ${TARGET_BRANCH}:"
            echo "${CHERRYPICK_OUT}"
            git cherry-pick --abort || true
            cd "${GITHUB_WORKSPACE}"
            git worktree remove -f ${WORKTREE}
            exit 1
          fi

          echo "branch=${BACKPORT_BRANCH}" >> "$GITHUB_OUTPUT"
          echo "branch-from=$(git rev-parse ${TARGET_BRANCH})" >> "$GITHUB_OUTPUT"
          echo "commit=$(git rev-parse HEAD)" >> "$GITHUB_OUTPUT"
          echo "target-branch=${TARGET_BRANCH}" >> "$GITHUB_OUTPUT"

      - name: Push Commit
        uses: DataDog/commit-headless@05d7b7ee023e2c7d01c47832d420c2503cd416f3 # action/v2.0.3
        with:
          branch: ${{ steps.create-commit.outputs.branch }}
          head-sha: ${{ steps.create-commit.outputs.branch-from }}
          target: "DataDog/dd-trace-py"
          create-branch: true
          command: push
          commits: ${{ steps.create-commit.outputs.commit }}
          force: true

      - name: Create PR
        env:
          PR_TITLE: ${{ github.event.pull_request.title }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          TARGET_BRANCH: ${{ steps.create-commit.outputs.target-branch }}
          BACKPORT_BRANCH: ${{ steps.create-commit.outputs.branch }}
          GH_TOKEN: ${{ steps.octo-sts.outputs.token }}
        run: |
          set +e
          EXISTING_PR=$(gh pr list --state open --base ${TARGET_BRANCH} --head ${BACKPORT_BRANCH} --json number --jq '.[0].number' 2>&1)
          GH_PR_LIST_STATUS=$?
          set -e
          if [ "${GH_PR_LIST_STATUS}" -ne 0 ]; then
            echo "Failed to query existing backport PR for ${TARGET_BRANCH}:"
            echo "${EXISTING_PR}"
            exit 1
          fi
          if [ -z "${EXISTING_PR}" ]; then
            set +e
            CREATE_OUT=$(gh pr create \
              --title "${PR_TITLE} [backport ${TARGET_BRANCH}]" \
              --body "Backport #${PR_NUMBER} to ${TARGET_BRANCH}" \
              --base ${TARGET_BRANCH} \
              --head ${BACKPORT_BRANCH} 2>&1)
            GH_PR_CREATE_STATUS=$?
            set -e
            if [ "${GH_PR_CREATE_STATUS}" -ne 0 ]; then
              echo "Failed to create backport PR for ${TARGET_BRANCH}:"
              echo "${CREATE_OUT}"
              exit 1
            fi
          else
            echo "Backport PR already exists for ${TARGET_BRANCH}: #${EXISTING_PR}"
          fi