Make repo sync a pull operation

The action was defined as a push operation before

Author: rlazo

.github/workflows/private-mirror-sync.yml

@@ -1,19 +1,22 @@
 name: Private Mirror Sync
 
-concurrency:
-  group: ${{ github.workflow }}
-  cancel-in-progress: true
-
 on:
-  push:
-    branches:
-      - main
+  workflow_dispatch:
+  schedule:
+    - cron: '0 2 * * *'
 
 jobs:
   sync:
-    if: github.repository == 'firebase/firebase-android-sdk'
+    if: github.repository == 'FirebasePrivate/firebase-android-sdk'
     runs-on: ubuntu-latest
     steps:
+      - uses: actions/[email protected]
+        with:
+          repository: firebase/firebase-android-sdk
+          ref: main
+          fetch-depth: 0
+          submodules: true
+
       - uses: actions/[email protected]
         with:
           fetch-depth: 0