fix signing

.gitea/workflows/docker-builder.yml

@@ -231,8 +231,16 @@ jobs:
         with:
           name: sbom
           path: sbom.spdx.json
-
+          
+      - name: Install cosign
+        run: |
+          curl -sSfL https://github.com/sigstore/cosign/releases/latest/download/cosign-linux-amd64 \
+            -o /usr/local/bin/cosign
+          chmod +x /usr/local/bin/cosign
       
       - name: Sign image
-        run: cosign sign --key ${{ secrets.COSIGN_KEY }} ${IMAGE_NAME}:v${VERSION}
+        if: env.IS_TAG == 'true'
+        run: |
+          cosign sign --key ${{ secrets.COSIGN_KEY }} ${IMAGE_NAME}:${VERSION}
+