code: function setOptions(opts) {
    opts = opts || {};
  
    if ((!opts.src || !opts.dest) && opts._.length < 2) {
      var msg = 'please let me know your "src" and "dest" path. \n--> run "assets-bundler -h" for more info.';
      console.error(msg);
      if (opts.parent === 'cmd') process.exit(1);
    }
  
    if (!opts.src && opts._.length >= 2) opts.src = opts._[0];
    if (!opts.dest && opts._.length >= 2) opts.dest = opts._[1];
  
    opts.env = opts.env || process.env.NODE_ENV || defaultEnv;
    if (opts.env === 'dev') opts.env = 'development';
    if (opts.env === 'prod') opts.env = 'production';
  
    debug('options', opts);
    return opts;
  }
docs: /*
  private helper functions