extensions/gulp/src/main.ts/FolderDetector/hasGulpfile
class FolderDetector:	private async hasGulpfile(root: string): Promise<boolean | undefined> {

		for (const filename of await fs.promises.readdir(root)) {

			const ext = path.extname(filename);
			if (ext !== '.js' && ext !== '.mjs' && ext !== '.cjs' && ext !== '.ts') {
				continue;
			}

			if (!exists(filename)) {
				continue;
			}

			const basename = path.basename(filename, ext).toLowerCase();
			if (basename === 'gulpfile') {
				return true;
			}
			if (basename === 'gulpfile.esm') {
				return true;
			}
			if (basename === 'gulpfile.babel') {
				return true;
			}
		}

		return false;
	}