Add Git.destroy() that frees native repository

src/app/git.coffee

@@ -1,4 +1,6 @@
 $ = require 'jquery'
+_ = require 'underscore'
+Subscriber = require 'subscriber'
 
 module.exports =
 class Git
@@ -23,12 +25,17 @@ class Git
 
   constructor: (path) ->
     @repo = new GitRepository(path)
-    $(window).on 'focus', => @refreshIndex()
+    @subscribe $(window), 'focus', => @refreshIndex()
 
   refreshIndex: -> @repo.refreshIndex()
 
   getPath: -> @repo.getPath()
 
+  destroy: ->
+    @repo.destroy()
+    @repo = null
+    @unsubscribe()
+
   getWorkingDirectory: ->
     repoPath = @getPath()
     repoPath?.substring(0, repoPath.length - 6)
@@ -85,3 +92,5 @@ class Git
 
   isSubmodule: (path) ->
     @repo.isSubmodule(@relativize(path))
+
+_.extend Git.prototype, Subscriber

src/app/project.coffee

@@ -34,6 +34,8 @@ class Project
     grammarOverridesByPath: @grammarOverridesByPath
 
   destroy: ->
+    @repo?.destroy()
+    @repo = null
     editSession.destroy() for editSession in @getEditSessions()
 
   addGrammarOverrideForPath: (path, grammar) ->