code: public String getNameWithoutTag(String optionalRegistry) {
          StringBuilder ret = new StringBuilder();
          if (registry != null || optionalRegistry != null) {
              ret.append(registry != null ? registry : optionalRegistry).append("/");
          }
          ret.append(repository);
          return ret.toString();
      }
docs: Get the full name of this image like {@link #getNameWithoutTag()} does, but allow
  an optional registry. This registry is used when this image does not already
  contain a registry.
  
  @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>)