Add backmerge release workflow to automate merging changes from release/13.2 to main

.github/workflows/README.md

@@ -99,3 +99,26 @@ When you comment on a PR (not an issue), the workflow will automatically push ch
 ### Concurrency
 
 The workflow uses concurrency groups based on the issue/PR number to prevent race conditions when multiple commands are issued on the same issue.
+
+## Backmerge Release Workflow
+
+The `backmerge-release.yml` workflow automatically creates PRs to merge changes from `release/13.2` back into `main`.
+
+### Schedule
+
+Runs daily at 00:00 UTC (4pm PT during standard time, 5pm PT during daylight saving time). Can also be triggered manually via `workflow_dispatch`.
+
+### Behavior
+
+1. **Change Detection**: Checks if `release/13.2` has commits not in `main`
+2. **PR Creation**: If changes exist, creates a PR to merge `release/13.2` → `main`
+3. **Auto-merge**: Enables GitHub's auto-merge feature, so the PR merges automatically once approved
+4. **Conflict Handling**: If merge conflicts occur, creates an issue instead of a PR
+
+### Assignees
+
+PRs and conflict issues are automatically assigned to @joperezr and @radical.
+
+### Manual Trigger
+
+To trigger manually, go to Actions → "Backmerge Release to Main" → "Run workflow".

.github/workflows/backmerge-release.yml

@@ -0,0 +1,152 @@
+name: Backmerge Release to Main
+
+on:
+  schedule:
+    - cron: '0 0 * * *'  # Runs daily at 00:00 UTC (16:00 PST / 17:00 PDT)
+  workflow_dispatch:      # Allow manual trigger
+
+permissions:
+  contents: write
+  pull-requests: write
+  issues: write
+
+jobs:
+  backmerge:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    if: ${{ github.repository_owner == 'dotnet' }}
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
+        with:
+          fetch-depth: 0  # Full history needed for merge
+
+      - name: Check for changes to backmerge
+        id: check
+        run: |
+          git fetch origin main release/13.2
+          BEHIND_COUNT=$(git rev-list --count origin/main..origin/release/13.2)
+          echo "behind_count=$BEHIND_COUNT" >> $GITHUB_OUTPUT
+          if [ "$BEHIND_COUNT" -gt 0 ]; then
+            echo "changes=true" >> $GITHUB_OUTPUT
+            echo "Found $BEHIND_COUNT commits in release/13.2 not in main"
+          else
+            echo "changes=false" >> $GITHUB_OUTPUT
+            echo "No changes to backmerge - release/13.2 is up-to-date with main"
+          fi
+
+      - name: Attempt merge and create branch
+        if: steps.check.outputs.changes == 'true'
+        id: merge
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+          git checkout origin/main
+          git checkout -b backmerge/release-13.2-to-main
+
+          # Attempt the merge
+          if git merge origin/release/13.2 --no-edit; then
+            echo "merge_success=true" >> $GITHUB_OUTPUT
+            git push origin backmerge/release-13.2-to-main --force
+            echo "Merge successful, branch pushed"
+          else
+            echo "merge_success=false" >> $GITHUB_OUTPUT
+            git merge --abort
+            echo "Merge conflicts detected"
+          fi
+
+      - name: Create Pull Request
+        if: steps.check.outputs.changes == 'true' && steps.merge.outputs.merge_success == 'true'
+        id: create-pr
+        uses: dotnet/actions-create-pull-request@e8d799aa1f8b17f324f9513832811b0a62f1e0b1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          head: backmerge/release-13.2-to-main
+          base: main
+          title: "[Automated] Backmerge release/13.2 to main"
+          labels: area-engineering-systems
+          body: |
+            ## Automated Backmerge
+
+            This PR merges changes from `release/13.2` back into `main`.
+
+            **Commits to merge:** ${{ steps.check.outputs.behind_count }}
+
+            This PR was created automatically to keep `main` up-to-date with release branch changes.
+            Once approved, it will auto-merge.
+
+            ---
+            *This PR was generated by the [backmerge-release](${{ github.server_url }}/${{ github.repository }}/actions/workflows/backmerge-release.yml) workflow.*
+
+      - name: Add assignees and enable auto-merge
+        if: steps.create-pr.outputs.pull-request-number
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh pr edit ${{ steps.create-pr.outputs.pull-request-number }} --add-assignee joperezr,radical
+          gh pr merge ${{ steps.create-pr.outputs.pull-request-number }} --auto --merge
+
+      - name: Create issue for merge conflicts
+        if: steps.check.outputs.changes == 'true' && steps.merge.outputs.merge_success == 'false'
+        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea  # v7.0.1
+        with:
+          script: |
+            const workflowRunUrl = `${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`;
+
+            // Check if there's already an open issue for this
+            const existingIssues = await github.rest.issues.listForRepo({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              state: 'open',
+              labels: 'backmerge-conflict',
+              creator: 'github-actions[bot]'
+            });
+
+            if (existingIssues.data.length > 0) {
+              console.log(`Existing backmerge conflict issue found: #${existingIssues.data[0].number}`);
+              // Add a comment to the existing issue
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: existingIssues.data[0].number,
+                body: `⚠️ Merge conflicts still exist.\n\n**Workflow run:** ${workflowRunUrl}\n\nPlease resolve the conflicts manually.`
+              });
+              return;
+            }
+
+            // Create a new issue
+            const issueBody = [
+              '## Backmerge Conflict',
+              '',
+              'The automated backmerge from `release/13.2` to `main` failed due to merge conflicts.',
+              '',
+              '### What to do',
+              '',
+              '1. Checkout main and attempt the merge locally:',
+              '   ```bash',
+              '   git checkout main',
+              '   git pull origin main',
+              '   git merge origin/release/13.2',
+              '   ```',
+              '2. Resolve the conflicts',
+              '3. Push the merge commit or create a PR manually',
+              '',
+              '### Details',
+              '',
+              `**Workflow run:** ${workflowRunUrl}`,
+              '**Commits to merge:** ${{ steps.check.outputs.behind_count }}',
+              '',
+              '---',
+              `*This issue was created automatically by the [backmerge-release](${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/workflows/backmerge-release.yml) workflow.*`
+            ].join('\n');
+
+            await github.rest.issues.create({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              title: '[Backmerge] Merge conflicts between release/13.2 and main',
+              body: issueBody,
+              assignees: ['joperezr', 'radical'],
+              labels: ['area-engineering-systems', 'backmerge-conflict']
+            });

.github/workflows/ci.yml

@@ -43,6 +43,7 @@ jobs:
             eng/pipelines/.*
             eng/test-configuration.json
             \.github/workflows/apply-test-attributes.yml
+            \.github/workflows/backmerge-release.yml
             \.github/workflows/backport.yml
             \.github/workflows/dogfood-comment.yml
             \.github/workflows/generate-api-diffs.yml