name: Backport merged pull request

# Automates cherry-picking merged PRs onto release branches.
# - Label a merged PR with e.g. `backport release-1.17` to backport on merge.
# - Or comment `/backport release-1.17` or `/cherrypick release-1.17` on a merged PR.
# See: https://github.com/velero-io/velero/issues/9603

on:
  pull_request_target:
    types: [closed]
  issue_comment:
    types: [created]

permissions: {}

jobs:
  backport:
    name: Backport pull request
    # Exclude comments from the backport-action bot (user id 97796249) to prevent
    # recursive triggers. The bot does not post /backport commands, so startsWith
    # already blocks recursion; the id check is defense in depth.
    if: >
      github.repository == 'velero-io/velero' &&
      (
        (
          github.event_name == 'pull_request_target' &&
          github.event.pull_request.merged &&
          contains(toJSON(github.event.pull_request.labels.*.name), '"backport ')
        ) || (
          github.event_name == 'issue_comment' &&
          github.event.issue.pull_request &&
          github.event.comment.user.id != 97796249 &&
          contains(
            fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'),
            github.event.comment.author_association
          ) &&
          (
            startsWith(github.event.comment.body, '/backport') ||
            startsWith(github.event.comment.body, '/cherrypick')
          )
        )
      )
    runs-on: ubuntu-latest
    permissions:
      contents: write # push backport branches and comment
      pull-requests: write # open backport PRs
    steps:
      - name: Parse target branches from comment
        id: parse
        if: github.event_name == 'issue_comment'
        env:
          COMMENT_BODY: ${{ github.event.comment.body }}
        run: |
          # First line only; strip /backport or /cherrypick prefix.
          # Remaining text is a space-delimited list of target branches
          # (may be empty, falls back to labels).
          line=$(printf '%s' "$COMMENT_BODY" | head -n1 | tr -d '\r')
          branches=$(printf '%s' "$line" | sed -E 's|^/(backport|cherrypick)[[:space:]]*||')
          echo "branches=${branches}" >> "$GITHUB_OUTPUT"

      - uses: actions/checkout@v7
        with:
          fetch-depth: 0

      - name: Create backport pull requests
        # Pin to commit SHA: workflow has contents/pull-requests write.
        uses: korthout/backport-action@2e830a1d0b8269505846ddd407a70876913ad1f8 # v4.6.0
        with:
          # Labels like `backport release-1.17` select the target branch.
          label_pattern: '^backport ([^ ]+)$'
          # Prefer draft PRs with conflict markers over failing the job silently.
          experimental: |
            {
              "conflict_resolution": "draft_commit_conflicts"
            }
          # Empty when triggered by merge labels; set when `/backport` or `/cherrypick` includes branches.
          target_branches: ${{ steps.parse.outputs.branches }}
          github_token: ${{ secrets.GITHUB_TOKEN }}