backport-to-develop.yml

name: Automatic Backport to Develop

on:
  pull_request:
    types: [closed]
    branches: [main]

permissions:
  contents: read
  pull-requests: write
  issues: write

jobs:
  create-backport-pr:
    # Only run if the PR was actually merged (not just closed)
    if: github.event.pull_request.merged == true
    runs-on: ubuntu-latest
    
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Get merged branch name
        id: get-branch
        env:
          BRANCH_NAME: ${{ github.event.pull_request.head.ref }}
          HEAD_REPO: ${{ github.event.pull_request.head.repo.full_name }}
        run: |
          # Get the head branch name and repo from the merged PR
          echo "branch-name=$BRANCH_NAME" >> $GITHUB_OUTPUT
          echo "head-repo=$HEAD_REPO" >> $GITHUB_OUTPUT
          echo "Merged branch: $BRANCH_NAME from $HEAD_REPO"

      - name: Check if branch exists
        id: check-branch
        env:
          HEAD_REF: ${{ steps.get-branch.outputs.branch-name }}
          HEAD_REPO: ${{ steps.get-branch.outputs.head-repo }}
        run: |
          # Check if the branch still exists on the fork remote
          if git ls-remote "https://github.com/${HEAD_REPO}.git" "refs/heads/${HEAD_REF}" | grep -q "refs/heads/${HEAD_REF}"; then
            echo "branch-exists=true" >> $GITHUB_OUTPUT
            echo "Branch $HEAD_REF exists in $HEAD_REPO and can be used for backport"
          else
            echo "branch-exists=false" >> $GITHUB_OUTPUT
            echo "Branch $HEAD_REF no longer exists in $HEAD_REPO, cannot create backport PR"
          fi

      - name: Create backport PR
        if: steps.check-branch.outputs.branch-exists == 'true'
        uses: actions/github-script@v7
        env:
          BRANCH_NAME: ${{ steps.get-branch.outputs.branch-name }}
          ORIGINAL_PR_NUMBER: ${{ github.event.pull_request.number }}
          ORIGINAL_PR_TITLE: ${{ github.event.pull_request.title }}
          ORIGINAL_PR_BODY: ${{ github.event.pull_request.body }}
          ORIGINAL_PR_AUTHOR: ${{ github.event.pull_request.user.login }}
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          script: |
            const branchName = process.env.BRANCH_NAME;
            const originalPrNumber = process.env.ORIGINAL_PR_NUMBER;
            const originalPrTitle = process.env.ORIGINAL_PR_TITLE;
            const originalPrBody = process.env.ORIGINAL_PR_BODY || '';
            const originalPrAuthor = process.env.ORIGINAL_PR_AUTHOR;

            // Create the backport PR
            try {
              const response = await github.rest.pulls.create({
                owner: context.repo.owner,
                repo: context.repo.repo,
                title: `[Backport] ${originalPrTitle}`,
                head: branchName,
                base: 'develop',
                body: `## Automatic Backport\n\nThis is an automatic backport of PR #${originalPrNumber} by @${originalPrAuthor} to the \`develop\` branch.\n\n### Original PR Details:\n${originalPrBody}\n\n---\n*This PR was created automatically when #${originalPrNumber} was merged into \`main\`.*`,
                maintainer_can_modify: true
              });
              
              console.log(`✅ Successfully created backport PR #${response.data.number}`);
              console.log(`🔗 PR URL: ${response.data.html_url}`);
              
              // Add labels to the backport PR
              await github.rest.issues.addLabels({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: response.data.number,
                labels: ['backport', 'automated']
              });
              
            } catch (error) {
              console.error('❌ Failed to create backport PR:', error.message);
              
              // Check if it's a conflict or other specific error
              if (error.message.includes('No commits between')) {
                console.log('ℹ️ The branch is already up to date with develop - no backport needed');
              } else if (
                error.status === 422 &&
                error.response &&
                Array.isArray(error.response.data?.errors) &&
                error.response.data.errors.some(e =>
                  e.message && e.message.includes('A pull request already exists')
                )
              ) {
                console.log('ℹ️ A pull request already exists for this branch to develop');
              } else {
                // Re-throw for other errors to fail the workflow
                throw error;
              }
            }

      - name: Handle missing branch
        if: steps.check-branch.outputs.branch-exists == 'false'
        run: |
          echo "⚠️ Cannot create backport PR because the source branch no longer exists."
          echo "This typically happens when the branch was deleted after merging."
          echo "If a backport to develop is needed, it should be done manually."