Create backport PRs automatically (#3558)

# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.

# SPDX-License-Identifier: Apache-2.0

name: Open a backport PR to merge the release branch into main

on:

  # automatically called by release.yml

  workflow_dispatch:

  # can also be manually triggered when a patch fix is merged into the release branch and needs to be back-ported

  workflow_call:

    secrets:

      RELEASE_AUTOMATION_BOT_PAT:

        required: true

env:

  release_branch: smithy-rs-release-1.x.y

jobs:

  create-backport-pull-request:

    runs-on: ubuntu-latest

    steps:

    - name: Checkout

      uses: actions/checkout@v4

      with:

        token: ${{ secrets.RELEASE_AUTOMATION_BOT_PAT }}

    - name: Prepare backport branch

      id: backport-branch

      run: |

        # This step assumes the merge runs cleanly without conflicts, which should be the case when

        # this workflow is called by the release workflow right after a release tag has been created.

        git config --local user.name "AWS SDK Rust Bot"

        git config --local user.email "aws-sdk-rust-primary@amazon.com"

        git fetch

        git checkout origin/main

        backport_branch="merge-${{ env.release_branch }}-to-main-$(date +%s)"

        git checkout -b "${backport_branch}"

        git merge "origin/${{ env.release_branch }}" -m 'Merge remote-tracking branch "origin/${{ env.release_branch }}" into "merge-${{ env.release_branch }}-to-main"'

        git push origin HEAD

        echo "branch_name=${backport_branch}" > $GITHUB_OUTPUT

    - name: Create pull request

      env:

        GITHUB_TOKEN: ${{ secrets.RELEASE_AUTOMATION_BOT_PAT }}

      run: |

        gh pr create \

          --title "Merge ${{ env.release_branch }} into main" \

          --body "Merge it with \`gh pr merge --admin --merge\` or manually merge it with the merge commit (not squash merge)." \

          --base main \

          --head ${{ steps.backport-branch.outputs.branch_name }} \

          --label "needs-sdk-review" \

          --draft

        # a manual PR to edit the current CHANGELOG.next.toml file and remove the released entries.

        git -c 'user.name=AWS SDK Rust Bot' -c 'user.email=aws-sdk-rust-primary@amazon.com' commit CHANGELOG.next.toml --message "Remove released entries from \`CHANGELOG.next.toml\`"

        git push origin main

  open-backport-pull-request:

    name: Open backport pull request to merge the release branch back to main

    needs:

    - trim-changelog-next-on-main

    # See https://github.com/actions/runner/issues/2205#issuecomment-1381988186 for details on the workaround

    if: inputs.dry_run == false && always() && needs.trim-changelog-next-on-main.result == 'success'

    uses: ./.github/workflows/backport-pull-request.yml

    secrets:

      RELEASE_AUTOMATION_BOT_PAT: ${{ secrets.RELEASE_AUTOMATION_BOT_PAT }}