name: Backport to older releases
on:
  push:
    branches:
    - main

jobs:

  backport:
    name: Backport change to branch ${{ matrix.branch }}
    continue-on-error: true
    strategy:
      fail-fast: false
      matrix:
        branch: [ 'release-1.0', 'release-0.28', 'release-0.27' ]

    runs-on: ubuntu-20.04

    steps:
    - name: Check out code
      uses: actions/checkout@v1
      with:
        fetch-depth: 0
    - name: Create a cherry-pick PR
      run: |
        if ! git diff --quiet HEAD^ HEAD -- vendor/libgit2; then
          echo '::warning::Skipping cherry-pick since it is a vendored libgit2 bump'
          exit 0
        fi

        BRANCH_NAME="cherry-pick-${{ github.run_id }}-${{ matrix.branch }}"

        # Setup usernames and authentication
        git config --global user.name "${{ github.actor }}"
        git config --global user.email "${{ github.actor }}@users.noreply.github.com"
        cat <<- EOF > $HOME/.netrc
        machine github.com
        login ${{ github.actor }}
        password ${{ secrets.GITHUB_TOKEN }}
        machine api.github.com
        login ${{ github.actor }}
        password ${{ secrets.GITHUB_TOKEN }}
        EOF
        chmod 600 $HOME/.netrc

        # Create the cherry-pick commit and create the PR for it.
        git checkout "${{ matrix.branch }}"
        git switch -c "${BRANCH_NAME}"
        git cherry-pick -x "${{ github.sha }}"
        git push --set-upstream origin "${BRANCH_NAME}"
        GITHUB_TOKEN="${{ secrets.GITHUB_TOKEN }}" gh pr create \
          --base "${{ matrix.branch }}" \
          --title "$(git --no-pager show --format="%s" --no-patch HEAD)" \
          --body "$(git --no-pager show --format="%b" --no-patch HEAD)"