support for tikz externalize

make copy of main file as output.tex for tikz externalize

test/unit/coffee/TikzManager.coffee

@@ -0,0 +1,65 @@
+SandboxedModule = require('sandboxed-module')
+sinon = require('sinon')
+require('chai').should()
+modulePath = require('path').join __dirname, '../../../app/js/TikzManager'
+
+describe 'TikzManager', ->
+	beforeEach ->
+		@TikzManager = SandboxedModule.require modulePath, requires:
+			"fs": @fs = {}
+			"logger-sharelatex": @logger = {log: () ->}
+
+	describe "needsOutputFile", ->
+		it "should return true if there is a usepackage{tikz}", ->
+			@TikzManager.needsOutputFile("main.tex", [
+				{ path: 'foo.tex' },
+				{ path: 'main.tex', content:'foo \\usepackage{tikz}' }
+			]).should.equal true
+
+		it "should return true if there is a usepackage{pgf}", ->
+			@TikzManager.needsOutputFile("main.tex", [
+				{ path: 'foo.tex'},
+				{ path: 'main.tex', content:'foo \\usepackage{pgf}' }
+			]).should.equal true
+
+		it "should return false if there is no usepackage{tikz} or {pgf}", ->
+			@TikzManager.needsOutputFile("main.tex", [
+				{ path: 'foo.tex' },
+				{ path: 'main.tex', content:'foo \\usepackage{bar}' }
+			]).should.equal false
+
+		it "should return false if there is already an output.tex file", ->
+			@TikzManager.needsOutputFile("main.tex", [
+				{ path: 'foo.tex' },
+				{ path: 'main.tex' },
+				{ path: 'output.tex' }
+			]).should.equal false
+
+	describe "injectOutputFile", ->
+		beforeEach ->
+			@rootDir = "/mock"
+			@filename = "filename.tex"
+			@callback = sinon.stub()
+			@content = '''
+				\\documentclass{article}
+				\\usepackage{tikz}
+				\\begin{document}
+				Hello world
+				\\end{document}
+			'''
+			@fs.readFile = sinon.stub().callsArgWith(2, null, @content)
+			@fs.writeFile = sinon.stub().callsArg(3)
+			@TikzManager.injectOutputFile @rootDir, @filename, @callback
+
+		it "should read the file", ->
+			@fs.readFile
+				.calledWith("#{@rootDir}/#{@filename}", "utf8")
+				.should.equal true
+
+		it "should write out the same file as output.tex", ->
+			@fs.writeFile
+				.calledWith("#{@rootDir}/output.tex", @content, {flag: 'wx'})
+				.should.equal true
+
+		it "should call the callback", ->
+			@callback.called.should.equal true