Don't destroy buffer when underlying file is deleted.

spec/text-buffer-spec.coffee

@@ -1330,13 +1330,10 @@ describe "TextBuffer", ->
           done()
         fs.removeSync(filePath)
 
-      it "retains its path and reports the buffer as not modified", ->
-        # FIXME: This doesn't pass on Linux
-        return if process.platform is 'linux'
-
-        expect(bufferToDelete.getPath()).toBe filePath
-        expect(bufferToDelete.isModified()).toBeFalsy()
-
+      it "unsets its path and reports the buffer as modified", ->
+        expect(bufferToDelete.getPath()).toBe undefined
+        expect(bufferToDelete.file).toBe null
+        expect(bufferToDelete.isModified()).toBeTruthy()
 
     describe "when the file is deleted", ->
       it "notifies all onDidDelete listeners ", (done) ->

src/text-buffer.coffee

@@ -50,6 +50,9 @@ class TextBuffer
   #   * `load` A {Boolean}, `true` to asynchronously load the buffer from disk
   #     after initialization.
   #   * `text` The initial {String} text of the buffer.
+  #   * `shouldDestroyOnFileDelete` A {Function} that returns a {Boolean}
+  #     indicating whether the buffer should be destroyed if its file is
+  #     deleted.
   constructor: (params) ->
     text = params if typeof params is 'string'
 
@@ -79,6 +82,8 @@ class TextBuffer
     @transactCallDepth = 0
     @digestWhenLastPersisted = params?.digestWhenLastPersisted ? false
 
+    @shouldDestroyOnFileDelete = params?.shouldDestroyOnFileDelete ? -> false
+
     @setPath(params.filePath) if params?.filePath
     @load() if params?.load
 
@@ -1472,14 +1477,23 @@ class TextBuffer
       if modified
         @updateCachedDiskContents()
       else
-        @destroy()
+        if @shouldDestroyOnFileDelete()
+          @destroy()
+        else
+          @unsubscribeFromFile()
 
     @fileSubscriptions.add @file.onDidRename =>
       @emitter.emit 'did-change-path', @getPath()
 
     @fileSubscriptions.add @file.onWillThrowWatchError (errorObject) =>
       @emitter.emit 'will-throw-watch-error', errorObject
 
+  unsubscribeFromFile: ->
+    @fileSubscriptions?.dispose()
+    @setPath(null)
+    @conflict = false
+    @cachedDiskContents = null
+
   createMarkerSnapshot: ->
     snapshot = {}
     for markerLayerId, markerLayer of @markerLayers