Function exists

packages/generator-react-server/test/app.js:95–102

(filename, dir)

});

function exists(filename, dir) {
	filename = path.join(dir, filename);
	return new Promise((resolve) => {
		fs.access(filename, fs.F_OK, (err) => {
			resolve(!err);
		});
	});
}

function readFile(filename, dir) {
	filename = path.join(dir, filename);