code: public static NFSFileVec make(File f) {
      Futures fs = new Futures();
      NFSFileVec nfs = make(f, fs);
      fs.blockForPending();
      return nfs;
    }
docs: Make a new NFSFileVec key which holds the filename implicitly.  This name
  is used by the Chunks to load data on-demand.  Blocking
  @return  A NFSFileVec mapped to this file.