update action

.gitea/workflows/github_mirror.yaml

@@ -14,6 +14,13 @@ jobs:
     runs-on: main
     steps:
 
+      - name: Init repo
+        run: |
+          git init
+          git remote add origin "${GT_SERVER_URL}/${GT_REPO}.git"
+          git fetch --depth=1 origin main
+          git checkout -b main FETCH_HEAD
+
       - name: Add GitHub remote
         env:
           GH_USER: ${{ secrets.GH_USER }}