Show spinner when loading MR diff

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/javascripts/merge_request.js.coffee

@@ -109,10 +109,10 @@ class MergeRequest
       type: 'GET'
       url: this.$('.merge-request-tabs .diffs-tab a').attr('href')
       beforeSend: =>
-        this.$('.status').addClass 'loading'
+        this.$('.mr-loading-status .loading').show()
       complete: =>
         @diffs_loaded = true
-        this.$('.status').removeClass 'loading'
+        this.$('.mr-loading-status .loading').hide()
       success: (data) =>
         this.$(".diffs").html(data.html)
       dataType: 'json'

app/views/projects/merge_requests/_show.html.haml

@@ -31,7 +31,8 @@
       = render "projects/merge_requests/show/diffs"
   .notes.tab-content.voting_notes#notes{ class: (controller.action_name == 'show') ? "" : "hide" }
     = render "projects/notes/notes_with_form"
-  .status
+  .mr-loading-status
+    = spinner
 
 :javascript
   var merge_request;