code: function scan (basePath, targetPath, sourceCode)
    {
      var match;
      while ((match = MATCH_URLS.exec (sourceCode))) {
        var url = match[2];
        if (!url.match (/^http/i) && url[0] !== '/') { // Skip absolute URLs
          var absSrcPath = path.resolve (basePath, url)
            , absDestPath = path.resolve (targetPath, options.targetDir, url)
            , relDestPath = path.relative (targetPath, absDestPath);
          if (relDestPath[0] === '.')
            return util.warn ('Relative asset url falls outside the build folder: <cyan>%</cyan>%', url, util.NL);
          if (exportedAssets[absDestPath]) // skip already exported asset
            continue;
          else exportedAssets[absDestPath] = true;
          var absTargetFolder = path.dirname (absDestPath);
          grunt.file.mkdir (absTargetFolder);
          if (options.symlink)
            fs.symlinkSync (absSrcPath, absDestPath);
          else grunt.file.copy (absSrcPath, absDestPath);
        }
      }
    }
docs: -------------------------------------------------------------------------------------------------------------------- PRIVATE -------------------------------------------------------------------------------------------------------------------- 
  Scans a stylesheet for asset URL references and copies the assets to the build folder.
  @private
  @param {string} basePath
  @param {string} targetPath
  @param {string} sourceCode