code: public Zips addFile(File file, FileFilter filter) {
      return this.addFile(file, false, filter);
    }
docs: Adds a file entry. If given file is a dir, adds it and all subfiles recursively.
  Adding takes precedence over removal of entries.
  
  @param file file to add.
  @param filter a filter to accept files for adding, null means all files are accepted
  @return this Zips for fluent api