Use History.js for better Tree browsing

Closes #1578

app/assets/javascripts/tree.js.coffee

@@ -8,9 +8,6 @@ $ ->
     $('#tree-slider .tree-item-file-name a, .breadcrumb li > a').live "click", ->
       $("#tree-content-holder").hide("slide", { direction: "left" }, 150)
 
-    $('.project-refs-form').live
-      "ajax:beforeSend": -> $("#tree-content-holder").hide("slide", { direction: "left" }, 150)
-
     # Make the entire tree-item row clickable, but not if clicking another link (like a commit message)
     $("#tree-slider .tree-item").live 'click', (e) ->
       $('.tree-item-file-name a', this).trigger('click') if (e.target.nodeName != "A")
@@ -19,3 +16,24 @@ $ ->
     $('#tree-slider .tree-item-file-name a, .breadcrumb a, .project-refs-form').live
       "ajax:beforeSend": -> $('.tree_progress').addClass("loading")
       "ajax:complete":   -> $('.tree_progress').removeClass("loading")
+
+# Maintain forward/back history while browsing the file tree
+
+((window) ->
+  History = window.History
+  $ = window.jQuery
+  document = window.document
+
+  # Check to see if History.js is enabled for our Browser
+  unless History.enabled
+    return false
+
+  $ ->
+    $('#tree-slider .tree-item-file-name a, .breadcrumb li > a').live 'click', (e) ->
+      History.pushState(null, null, $(@).attr('href'))
+      return false
+
+    History.Adapter.bind window, 'statechange', ->
+      state = History.getState()
+      window.ajaxGet(state.url)
+)(window)