safer login

.github/workflows/package.yaml

@@ -46,13 +46,12 @@ jobs:
       - name: Build Docker Image
         run: docker build --tag $IMAGE_NAME --label "runnumber=${GITHUB_RUN_ID}" docker/
 
-      - name: Log in to registry
-        run: |
-          if [[ ${{ github.ref }} == 'refs/head/master' ]]; then
-            echo "${{ secrets.GITHUB_TOKEN }}" | docker login ghcr.io -u $ --password-stdin
-          else
-            echo "Skipped on PRs"
-          fi
+      - name: login to GitHub Container Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Push image
         run: |