public String getFullName(String optionalRegistry) {
        String fullName = getNameWithoutTag(optionalRegistry);
        if (tag != null) {
            fullName = fullName +  ":" + tag;
        }
        if(digest != null) {
            fullName = fullName + "@" + digest;
        }
        return fullName;
    }
Get the full name of this image like {@link #getFullName(String)} does, but allow
an optional registry. This registry is used when this image does not already
contain a registry. If no tag was provided in the initial name, <code>latest</code> is used.

@param optionalRegistry optional registry to use when this image does not provide
                        a registry. Can be null in which case no optional registry is used*
@return full name with original registry (if set) or optional registry (if not <code>null</code>).
src/main/java/io/fabric8/maven/docker/util/ImageName.java