Add upstream sync script

Author: Fudster

.github/workflows/upsteam-sync.yml

@@ -0,0 +1,44 @@
+name: Sync with upstream
+on:
+  schedule:
+    - cron: '0 6 * * *'  # Run daily at 6 AM UTC
+  workflow_dispatch:  # Allow manual trigger
+
+jobs:
+  sync:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          token: ${{ secrets.GITHUB_TOKEN }}
+      
+      - name: Add upstream remote
+        run: git remote add upstream https://github.com/supabase/realtime
+      
+      - name: Fetch upstream and origin
+        run: |
+          git fetch upstream
+          git fetch origin
+      
+      - name: Check for changes
+        id: check
+        run: |
+          # Check if upstream branch exists and compare, otherwise compare with HEAD
+          if git rev-parse --verify origin/upstream >/dev/null 2>&1; then
+            if git diff --quiet origin/upstream upstream/main; then
+              echo "changes=false" >> $GITHUB_OUTPUT
+            else
+              echo "changes=true" >> $GITHUB_OUTPUT
+            fi
+          else
+            # First time running, upstream branch doesn't exist yet
+            echo "changes=true" >> $GITHUB_OUTPUT
+          fi
+      
+      - name: Sync if changes exist
+        if: steps.check.outputs.changes == 'true'
+        run: |
+          git checkout -B upstream
+          git merge upstream/main
+          git push origin upstream