code: function filter(options, includes, root, filepath, stat) {
    var paths = path.relative(root, filepath).split(path.sep);
    // always include test/tests directory when running jpm test
    if (options.command === "test") {
      if (/^tests?$/.test(paths[0])) {
        if (paths.length === 1 && stat.isDirectory()) {
          return true;
        }
        if (paths.length > 1) {
          return true;
        }
      }
    }
    return includes.indexOf(filepath) !== -1;
  }
docs: Filter for deciding what is included in a xpi based on a list of included files