change checkout to version 4 (#64)

Author: aOelschlager

.github/workflows/gitlab-mirror.yml

@@ -9,7 +9,9 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
     - name: Mirror + trigger CI
       uses: SvanBoxel/gitlab-mirror-and-ci-action@master
       with: