add additional step for tag value

Author: jarededwards

.github/workflows/publish.yaml

@@ -18,10 +18,14 @@ jobs:
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - 
+        name: Get the version
+        id: get_version
+        run: echo ::set-output name=VERSION::$(echo $GITHUB_REF | cut -d / -f 3)
       -
         name: Build and push
         id: docker_build
         uses: docker/build-push-action@v2
         with:
           push: true
-          tags: kubefirst/nebulous:${GITHUB_REF##*/}
+          tags: kubefirst/nebulous:${{ steps.get_version.outputs.VERSION }}