code: public String getFullName(String optionalRegistry) {
          String fullName = getNameWithoutTag(optionalRegistry);
          if (tag != null) {
              fullName = fullName +  ":" + tag;
          }
          if(digest != null) {
              fullName = fullName + "@" + digest;
          }
          return fullName;
      }
docs: 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>).