Merge branch 'show-message-to-signed-out-users-to-sign-in-if-they-want-to-comment' into 'master'

Adds disabled comment field and disabled avatar.

Fixes #3540

![Screen_Shot_2016-01-20_at_12.13.29_AM](/uploads/673fb783e9aeae441df9c40bfe29ac1b/Screen_Shot_2016-01-20_at_12.13.29_AM.png)


See merge request !2508

app/assets/stylesheets/pages/merge_requests.scss

@@ -201,3 +201,39 @@
 .mr-source-target {
   line-height: 31px;
 }
+
+.disabled-comment-area {
+  padding: 16px 0;
+
+  .disabled-profile {
+    width: 40px;
+    height: 40px;
+    background: $border-gray-dark;
+    border-radius: 20px;
+    display: inline-block;
+    margin-right: 10px;
+  }
+
+  .disabled-comment {
+    background: $gray-light;
+    display: inline-block;
+    vertical-align: top;
+    height: 200px;
+    border-radius: 4px;
+    border: 1px solid $border-gray-normal;
+    padding-top: 90px;
+    text-align: center;
+    right: 20px;
+    position: absolute;
+    left: 70px;
+    margin-bottom: 20px;
+
+    span {
+      color: #B2B2B2;
+
+      a {
+        color: $md-link-color;
+      }
+    }
+  }
+}
\ No newline at end of file

app/views/projects/notes/_notes_with_form.html.haml

@@ -5,6 +5,16 @@
 .js-main-target-form
 - if can? current_user, :create_note, @project
   = render "projects/notes/form", view: diff_view
+- else
+  .disabled-comment-area
+    .disabled-profile
+    .disabled-comment
+      %span
+        Please
+        = link_to "register",new_user_session_path
+        or
+        = link_to "login",new_user_session_path
+        to post a comment
 
 :javascript
   var notes = new Notes("#{namespace_project_notes_path(namespace_id: @project.namespace, target_id: @noteable.id, target_type: @noteable.class.name.underscore)}", #{@notes.map(&:id).to_json}, #{Time.now.to_i}, "#{diff_view}")