fix: add checkout step

.gitea/workflows/ci.yml

@@ -4,4 +4,9 @@ jobs:
   test:
     runs-on: ubuntu-latest
     steps:
+      - name: Checkout
+        run: |
+          git clone https://${{ gitea.server }}/${{ gitea.repository }} .
+          git checkout ${{ gitea.sha }}
+
       - run: echo "CI passed"