'use strict';

var fs = require('fs');
var path = require('path');
var exec = require('child_process').exec;
var execSync = require('child_process').execSync;
var chalk = require('chalk');
var prompt = require('prompt');
var semver = require('semver');

// Use Yarn if available, it's much faster than the npm client.
// Return the version of yarn installed on the system, null if yarn is not available.
function getYarnVersionIfAvailable() {