Use file contents instead of md5 to determine disk change

spec/app/buffer-spec.coffee

@@ -3,7 +3,7 @@ Buffer = require 'buffer'
 fs = require 'fs'
 _ = require 'underscore'
 
-describe 'Buffer', ->
+fdescribe 'Buffer', ->
   [filePath, fileContents, buffer] = []
 
   beforeEach ->
@@ -95,7 +95,7 @@ describe 'Buffer', ->
       runs ->
         expect(changeHandler).not.toHaveBeenCalled()
 
-    describe "when the buffer's memory contents are the same as the *previous* disk contents", ->
+    describe "when the buffer is in an unmodified state before the on-disk change", ->
       it "changes the memory contents of the buffer to match the new disk contents and triggers a 'change' event", ->
         changeHandler = jasmine.createSpy('changeHandler')
         buffer.on 'change', changeHandler

src/app/buffer.coffee

@@ -76,10 +76,7 @@ class Buffer
     @setText(@cachedDiskContents)
 
   updateCachedDiskContents: ->
-    if fs.exists(@getPath())
-      @cachedDiskContents = fs.read(@getPath())
-    else
-      @cachedDiskContents = null
+    @cachedDiskContents = @file.read()
 
   getBaseName: ->
     @file?.getBaseName()
@@ -239,14 +236,9 @@ class Buffer
     unless path then throw new Error("Can't save buffer with no file path")
 
     @trigger 'before-save'
-
-    @file?.updateMd5()
     @setPath(path)
-
-    text = @getText()
-
-    @cachedDiskContents = text
-    @file.write(text)
+    @cachedDiskContents = @getText()
+    @file.write(@getText())
     @subscribeToFile()
     @trigger 'after-save'
 

src/app/file.coffee

@@ -6,13 +6,13 @@ _ = require 'underscore'
 module.exports =
 class File
   path: null
-  md5: null
+  cachedContents: null
 
   constructor: (@path) ->
     if @exists() and not fs.isFile(@path)
       throw new Error(@path + " is a directory")
 
-    @updateMd5() if @exists()
+    @read() if @exists()
 
   setPath: (@path) ->
 
@@ -23,16 +23,21 @@ class File
 
   write: (text) ->
     previouslyExisted = @exists()
+    @cachedContents = text
     fs.write(@getPath(), text)
-    @updateMd5()
     @subscribeToNativeChangeEvents() if not previouslyExisted and @subscriptionCount() > 0
 
+  read: (flushCache)->
+    if not @exists()
+      @cachedContents = null
+    else if not @cachedContents? or flushCache
+      @cachedContents = fs.read(@getPath())
+    else
+      @cachedContents
+
   exists: ->
     fs.exists(@getPath())
 
-  updateMd5: ->
-    @md5 = fs.md5ForPath(@path)
-
   afterSubscribe: ->
     @subscribeToNativeChangeEvents() if @exists() and @subscriptionCount() == 1
 
@@ -41,15 +46,15 @@ class File
 
   handleNativeChangeEvent: (eventType, path) ->
     if eventType is "remove"
+      @cachedContents = null
       @detectResurrectionAfterDelay()
     else if eventType is "move"
       @setPath(path)
       @trigger "move"
     else if eventType is "contents-change"
-      newMd5 = fs.md5ForPath(@getPath())
-      return if newMd5 == @md5
-
-      @md5 = newMd5
+      oldContents = @read()
+      newContents = @read(true)
+      return if oldContents == newContents
       @trigger 'contents-change'
 
   detectResurrectionAfterDelay: ->