docs: @Nullable
    public String prefixedCommitId() {
      if (abbreviatedObjectId.isPresent()) {
        String name = abbreviatedObjectId.get().name();
        return gPrefixedCommitId(name);
  
      } else if (commitId.isPresent()) {
        String name = commitId.get().name();
        return gPrefixedCommitId(name);
  
      } else {
        return null;
      }
    }