private String joinTail(String[] parts) {
        StringBuilder builder = new StringBuilder();
        for (int i = 1;i < parts.length; i++) {
            builder.append(parts[i]);
            if (i < parts.length - 1) {
                builder.append("/");
            }
        }
        return builder.toString();
    }
Create an image name with a tag. If a tag is provided (i.e. is not null) then this tag is used.
Otherwise the tag of the provided name is used (if any).

@param fullName The fullname of the image in Docker format. I
@param givenTag tag to use. Can be null in which case the tag specified in fullName is used.
src/main/java/io/fabric8/maven/docker/util/ImageName.java