Template of simple docker repository.
The Makefile is a simple wrapper for building and publishing docker images.
The image name IMAGE_NAME is determined from directory name. The image tag IMAGE_TAG is determined from current
git branch.
Make variables can be overridden in .env file. This is mainly used for setting REGISTRY, REGISTRY_USER,
DOCKER_BUILD_ARGS, DOCKER_RUN_ARGS or forcing IMAGE_TAG.