ci: use shell checkout on minimal runner

.gitea/workflows/container.yml

@@ -18,11 +18,17 @@ jobs:
       - name: Install build tools
         run: |
           apt-get update
-          DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends ca-certificates curl docker.io jq
+          DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends ca-certificates curl docker.io git jq
           rm -rf /var/lib/apt/lists/*
 
       - name: Check out repository
-        uses: actions/checkout@v4
+        shell: bash
+        run: |
+          set -euo pipefail
+          git init .
+          git remote add origin "${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}.git"
+          git fetch --depth=1 origin "${GITHUB_SHA}"
+          git checkout --detach FETCH_HEAD
 
       - name: Resolve upstream dependency versions
         shell: bash