harden update script and add bats CI coverage

.gitea/workflows/commit.yaml

@@ -8,10 +8,14 @@ jobs:
   test:
     runs-on: debian-latest
     steps:
-      - name: Show Debian version
-        run: cat /etc/os-release
-      - name: Test Deployment
-        run: echo "Deployment test"
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Install Bats
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y bats
+      - name: Run Shell Tests
+        run: bats tests/shell/git_update.bats
 
   deploy:
     runs-on: self-hosted