Quote variables when interpolated

Author: errordeveloper

.travis.yml

@@ -13,15 +13,15 @@ before_install:
   - make test-image deps
 
 env:
-  - GROUP=${FORK-:weaveworksdemos} COMMIT=$TRAVIS_COMMIT TAG=$TRAVIS_TAG REPO=front-end;
+  - GROUP="${FORK-:weaveworksdemos}" COMMIT="${TRAVIS_COMMIT}" TAG="${TRAVIS_TAG}" REPO=front-end;
 
 script:
   - make test
 
 after_success:
   - set -e
-  - if [ -z "$DOCKER_PASS" ]; then echo "Build triggered by external PR. Skipping docker push" && exit 0; fi
-  - docker login -u $DOCKER_USER -p $DOCKER_PASS;
+  - if [ -z "${DOCKER_PASS}" ]; then echo "Build triggered by external PR. Skipping docker push" && exit 0; fi
+  - docker login -u "${DOCKER_USER}" -p "${DOCKER_PASS}";
   - ./scripts/build.sh
   - ./test/container.sh
   - ./scripts/push.sh