Add fs.join

spec/stdlib/fs-spec.coffee

@@ -11,6 +11,12 @@ describe "fs", ->
         expect(fs.directory(require.resolve('fixtures/dir'))).toBe require.resolve('fixtures/dir/')
         expect(fs.directory(require.resolve('fixtures/dir/'))).toBe require.resolve('fixtures/dir/')
 
+  describe ".join(paths...)", ->
+    it "concatenates the given paths with the directory seperator", ->
+      expect(fs.join('a')).toBe 'a'
+      expect(fs.join('a', 'b', 'c')).toBe 'a/b/c'
+      expect(fs.join('/a/b/', 'c', 'd')).toBe '/a/b/c/d'
+      expect(fs.join('a', 'b/c/', 'd/')).toBe 'a/b/c/d/'
 
   describe ".async", ->
     describe ".listFiles(directoryPath, recursive)", ->

src/stdlib/fs.coffee

@@ -35,6 +35,11 @@ module.exports =
   exists: (path) ->
     OSX.NSFileManager.defaultManager.fileExistsAtPath_isDirectory path, null
 
+  join: (paths...) ->
+    return paths[0] if paths.length == 1
+    [first, rest...] = paths
+    first.replace(/\/?$/, "/") + @join(rest...)
+
   # Returns true if the file specified by path exists and is a
   # directory.
   isDirectory: (path) ->