message: build: fix container publish
diff: read -r -p "Do you have master checked out with most recent changes? [y/N] " response
  if [[ $response =~ ^([yY][eE][sS]|[yY])$ ]]
  then
  - TAG="$(git rev-parse master)"
  + export TAG="$(git rev-parse master)"
  docker-machine start default
  eval $(docker-machine env default)
  ./docker_build.sh
  