Set modified flag to true when there is a buffer change.

spec/app/buffer-spec.coffee

@@ -31,6 +31,32 @@ describe 'Buffer', ->
         buffer = new Buffer
         expect(buffer.getText()).toBe ""
 
+  describe "path-change event", ->
+    it "emits path-change event when path is changed", ->
+      eventHandler = jasmine.createSpy('eventHandler')
+      buffer.on 'path-change', eventHandler
+      buffer.setPath("moo.text")
+      expect(eventHandler).toHaveBeenCalledWith(buffer)
+
+  describe ".isModified()", ->
+    describe "when deserialized", ->
+      it "returns false", ->
+        buffer = Buffer.deserialize(buffer.serialize(), new Project)
+        expect(buffer.isModified()).toBe false
+
+        buffer = Buffer.deserialize((new Buffer).serialize(), new Project)
+        expect(buffer.isModified()).toBe false
+
+      it "returns is true if buffer no path and had changes", ->
+        buffer = new Buffer
+        buffer.insert([0,0], "oh hi")
+        expect(buffer.isModified()).toBe true
+
+    it "returns true when user changes buffer", ->
+      expect(buffer.isModified()).toBeFalsy()
+      buffer.insert([0,0], "hi")
+      expect(buffer.isModified()).toBe true
+
   describe '.deserialize(state, project)', ->
     project = null
 
@@ -365,7 +391,7 @@ describe 'Buffer', ->
 
         expect(ranges.length).toBe 2
 
-  describe "backwardsScanInRange(range, regex, fn)", ->
+  describe ".backwardsScanInRange(range, regex, fn)", ->
     describe "when given a regex with no global flag", ->
       it "calls the iterator with the last match for the given regex in the given range", ->
         matches = []
@@ -446,11 +472,3 @@ describe 'Buffer', ->
       expect(buffer.positionForCharacterIndex(30)).toEqual [1, 0]
       expect(buffer.positionForCharacterIndex(61)).toEqual [2, 0]
       expect(buffer.positionForCharacterIndex(408)).toEqual [12, 2]
-
-  describe "path-change event", ->
-    it "emits path-change event when path is changed", ->
-      eventHandler = jasmine.createSpy('eventHandler')
-      buffer.on 'path-change', eventHandler
-      buffer.setPath("moo.text")
-      expect(eventHandler).toHaveBeenCalledWith(buffer)
-

src/app/buffer.coffee

@@ -8,16 +8,19 @@ UndoManager = require 'undo-manager'
 module.exports =
 class Buffer
   @idCounter = 1
+  modified: null
   lines: null
   path: null
 
   @deserialize: (state, project) ->
     if state.path
-      project.open(state.path)
+      buffer = project.open(state.path)
     else
       buffer = project.bufferWithId(state.id) ? project.open()
       buffer.setText(state.text)
-      buffer
+      buffer.modified = state.modified
+
+    buffer
 
   constructor: (path) ->
     @id = @constructor.idCounter++
@@ -28,12 +31,13 @@ class Buffer
     else
       @setText('')
     @undoManager = new UndoManager(this)
+    @modified = false
 
   serialize: ->
     if @getPath()
       { path: @path }
     else
-      { text: @getText(), id: @id }
+      { text: @getText(), id: @id , modified: @modified}
 
   getPath: ->
     @path
@@ -139,6 +143,8 @@ class Buffer
       newTextLines[lastLineIndex] += suffix
 
     @lines[oldRange.start.row..oldRange.end.row] = newTextLines
+    @modified = true
+
     @trigger 'change', { oldRange, newRange, oldText, newText }
     newRange
 
@@ -164,6 +170,9 @@ class Buffer
     @setPath(path)
     @save()
 
+  isModified: ->
+    @modified
+
   getMode: ->
     return @mode if @mode
     extension = if @getPath() then @getPath().split('/').pop().split('.').pop() else null