Only push images built from master

.circleci/config.yml

@@ -10,5 +10,11 @@ jobs:
       - run: go get github.com/golang/dep/cmd/dep
       - run: dep ensure
       - run: make
-      - run: docker login -u "$DOCKER_USER" -p "$DOCKER_PASS" quay.io
-      - run: make publish-image
+
+      - deploy:
+          name: Maybe push master images
+          command: |
+            if [ -z "${CIRCLE_TAG}" -a "${CIRCLE_BRANCH}" == "master" ]; then
+              docker login -u "$DOCKER_USER" -p "$DOCKER_PASS" quay.io
+              make publish-image
+            fi