code: function fetchJSMapPairs(distFiles) {
    let jsFiles = indexByBaseFilename(fetchFilePathsByType(distFiles, '/', 'js'));
    return fetchFilePathsByType(distFiles, '/', 'map').map(mapFile => {
      let baseFileName = getBaseFilename(mapFile);
      return {
        mapFile: mapFile,
        jsFile: jsFiles[baseFileName]
      };
    });
  }
docs: This function takes all of the files in a build process, find the sourcemaps and their corresponding javascript files, and returns each matching pair as on object containing both the sourcemap and javascript file paths relative to the the build directory (meaning they will start with `/assets/`)