backport-fixup.yml

# Fixes up Mergify-created backport PRs to include necessary labels and other
# information for release notes generation

name: Backport Fixup

on:
  pull_request:
    types: [opened]
  workflow_dispatch:
    inputs:
      pr:
        description: 'Number of the Pull Request to Fixup'
        require: true

permissions:
  pull-requests: write
  contents: write

jobs:
  resolve_prs:
    name: Resolve PRs
    runs-on: ubuntu-22.04
    # If triggering PR actually is a backport, then original_pr will be set
    outputs:
        backport_pr: ${{ steps.backport.outputs.pr }}
        original_pr: ${{ steps.original.outputs.pr }}

    steps:
      - uses: actions/checkout@v3
      - name: Figure out backport PR number
        id: backport
        run: |
          if [[ -z "${{ inputs.pr }}" ]]; then
            echo "pr=${{ github.event.number }}" >> "$GITHUB_OUTPUT"
          else
            echo "pr=${{ inputs.pr }}" >> "$GITHUB_OUTPUT"
          fi
      - name: Figure out original PR number (if one exists)
        id: original
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          BP_PR=${{ steps.backport.outputs.pr }}
          TITLE=$(gh pr view --json title --jq '.title' $BP_PR)
          if [[ "$TITLE" =~ \(backport\ #([0-9]+)\) ]]; then
            echo "pr=${BASH_REMATCH[1]}" >> "$GITHUB_OUTPUT"
          else
            echo "$BP_PR is not a backport PR!" >> $GITHUB_STEP_SUMMARY
          fi

  fixup_backport:
    name: Fixup the backport PR
    runs-on: ubuntu-22.04
    needs: [resolve_prs]
    if: ${{ needs.resolve_prs.outputs.original_pr }}

    steps:
      - uses: actions/checkout@v3
      - name: Copy over labels
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          BP_PR=${{ needs.resolve_prs.outputs.backport_pr }}
          ORIG_PR=${{ needs.resolve_prs.outputs.original_pr }}

          # Long line but the paste joining must be done right away or we run into issues with spaces in labels
          LABELS=$(gh pr view --json labels --jq '.labels | .[].name | select(. != "Backported")' $ORIG_PR | paste -sd "," -)
          gh pr edit $BP_PR --add-label "$LABELS"
      - name: Copy over body
        env:
          GH_TOKEN: ${{ github.token }}
        run: |
          BP_PR=${{ needs.resolve_prs.outputs.backport_pr }}
          ORIG_PR=${{ needs.resolve_prs.outputs.original_pr }}

          gh pr view --json body --jq '.body' $ORIG_PR > orig_body.txt
          gh pr view --json body --jq '.body' $BP_PR > bp_body.txt

          if grep -q '# Original PR Body' bp_body.txt; then
            # Copy BP PR body but remove original PR body from bottom
            sed '/# Original PR Body/q' bp_body.txt > new_bp_body.txt
            echo "" >> new_bp_body.txt
          else
            cp bp_body.txt new_bp_body.txt
            echo -e "\n----\n\n# Original PR Body\n" >> new_bp_body.txt
          fi

          cat orig_body.txt >> new_bp_body.txt

          gh pr edit $BP_PR --body-file new_bp_body.txt