name: Sync default branches

on:
  push:
    branches:
      - main
      - master
  pull_request:
    paths:
      - .github/workflows/sync-default-branches.yml

permissions: {}

defaults:
  run:
    shell: bash -xeuo pipefail {0}

concurrency:
  group: "sync-default-branches-${{ github.ref }}"
  cancel-in-progress: true

jobs:
  sync:
    runs-on: ubuntu-latest
    permissions:
      contents: write
    steps:
      - name: Configure Git user
        uses: Homebrew/actions/git-user-config@main
        with:
          username: github-actions[bot]

      - name: Determine source and target branches
        id: branches
        run: |
          if [[ "${GITHUB_REF_NAME}" == "main" ]]; then
            target="master"
            source="main"
          else
            target="main"
            source="master"
          fi
          echo "target=${target}" >> "$GITHUB_OUTPUT"
          echo "source=${source}" >> "$GITHUB_OUTPUT"

      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          fetch-depth: 0
          persist-credentials: true

      - name: Setup target branch
        run: |
          git checkout "${TARGET_BRANCH}" || git checkout -b "${TARGET_BRANCH}"
          git reset --hard "origin/${SOURCE_BRANCH}"
        env:
          SOURCE_BRANCH: ${{ steps.branches.outputs.source }}
          TARGET_BRANCH: ${{ steps.branches.outputs.target }}

      - name: Push target branch
        if: github.ref == 'refs/heads/main' || github.ref == 'refs/heads/master'
        run: git push origin "${TARGET_BRANCH}" --force-with-lease
        env:
          TARGET_BRANCH: ${{ steps.branches.outputs.target }}