Refactor r() into utils

lib/utils.js

@@ -1,4 +1,6 @@
 'use strict'
+import { resolve, sep } from 'path'
+import _ from 'lodash'
 
 export function encodeHtml (str) {
   return str.replace(/</g, '&lt;').replace(/>/g, '&gt;')
@@ -74,3 +76,24 @@ export function chainFn (base, fn) {
     fn.apply(this, arguments)
   }
 }
+
+function wp (p) {
+  /* istanbul ignore if */
+  if (/^win/.test(process.platform)) {
+    p = p.replace(/\\/g, '\\\\')
+  }
+  return p
+}
+
+const reqSep = /\//g
+const sysSep = _.escapeRegExp(sep)
+const normalize = string => string.replace(reqSep, sysSep)
+
+export function r () {
+  let args = Array.from(arguments)
+  if (_.last(args).includes('~')) {
+    return wp(_.last(args))
+  }
+  args = args.map(normalize)
+  return wp(resolve.apply(null, args))
+}