Jo Liss joliss

helpers.copyPreserveSync (would need API change to do symlinks instead; possibly still optimizable without symlinks)
walkSync
helpers.hashTree (note: also duplicates stat calls with walkSync)
mkdir/mkdirp (probably unnecessary calls here)
rimraf via quick-temp via broccoli-writer (new API would move this from writer into core, but rimraf call is still necessary)
perhaps some suprising CPU sinks, like hashing crypto, path module, etc.

Breaking down what merge-trees spends time on, on a set of 500 small files:

walkSync 6 ms
pathManipulation 7 ms      <------- string stuff, doesn't hit file system
mkdir 1 ms
copy 71 ms     <------- clearly unacceptable, and gets much worse with big image files
mergeTotal 86 ms

	// === Identifier rewriting for the ES6 module transpiler ===

	// Proposal for minifier-friendly ES6 module transpiler output.
	// This is for cases where we don't require any existing module
	// format (AMD, CommonJS) and just want to emit a blackbox IIFE
	// that uses modules internally. Those cases are Ember's normal
	// global distribution (ember.min.js), as well as ES5 generated
	// by the upcoming ember-cli ES6 stack.

	// Do you all think this could work?

	~3607 bytes min.gz overhead from these kinds of declarations:

	define('somemod', ...
	...
	var rewatch = __dependency6__.rewatch; <-------------
	var finishChains = __dependency7__.finishChains; <-------------
	...

	There are 793 such lines, thus adding about 4.5 bytes in .min.gz size each.

	#!/bin/bash

	(
	echo "(function() {"
	for i in {0..9999}; do
	echo "
	var var$i = 1
	var read$i = function() {
	// Prevent inlining by feigning recursion
	if (!var$i) read$i()

	var outerVars = 10000
	var iterations = 100000

	src = ''
	src += '(function() {'
	for (var i = 0; i < outerVars / 3; i++) {
	src += ' var num' + i + ' = 1\n'
	src += ' var read' + i + ' = function() {\n'
	// Prevent inlining by feigning recursion
	src += ' if (!num' + i + ') read' + i + '()\n'

	#!/usr/bin/env node

	var fs = require('fs')
	var rimraf = require('rimraf')

	fs.mkdirSync('x')

	var string = ''
	for (var i = 0; i < 100; i++) {
	string += '1234567890'

	fs.mkdirSync('testdir')

	var obj = {
	'foo.txt': 'foo.txt contents',
	'subdir': {
	'bar.txt': 'bar.txt contents',
	}
	}

	writeSync('testdir', obj) // write foo.txt and subdir/bar.txt to disk

	[broccoli-filter] Copy time in TranspilerFilter: 23ms
	[broccoli-filter] Copy time in TranspilerFilter: 111ms <--------

	Slowest Trees \| Total
	-------------------------------+----------------
	TranspilerFilter \| 204ms <--------- probably this one - 50%?
	Concat \| 117ms
	TreeMerger \| 114ms
	TreeMerger \| 105ms

	###
	*= require jquery
	*= require underscore
	###