Add small visual improvements to merge request version switch

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

app/assets/stylesheets/pages/merge_requests.scss

@@ -375,5 +375,9 @@
 .mr-version-switch {
   background: $background-color;
   padding: $gl-btn-padding;
-  border-bottom: 1px solid $border-color;
+  color: $gl-placeholder-color;
+
+  a.btn-link {
+    color: $gl-dark-link-color;
+  }
 }

app/views/projects/merge_requests/show/_versions.html.haml

@@ -10,15 +10,18 @@
           - if latest_diff == @merge_request_diff
             #{"latest"}
           - else
-            #{@merge_request_diff.base_commit.short_id}..#{@merge_request_diff.head_commit.short_id}
+            #{@merge_request_diff.head_commit.short_id}
         %span.caret
       %ul.dropdown-menu.dropdown-menu-selectable
         - @merge_request.merge_request_diffs.each do |merge_request_diff|
           %li
             = link_to diffs_namespace_project_merge_request_path(@project.namespace, @project, @merge_request, diff_id: merge_request_diff.id), class: ('is-active' if merge_request_diff == @merge_request_diff) do
               %strong.monospace
-                #{merge_request_diff.base_commit.short_id}..#{merge_request_diff.head_commit.short_id}
+                #{merge_request_diff.head_commit.short_id}
               %br
               %small
-
                 = time_ago_with_tooltip(merge_request_diff.created_at)
+
+    .pull-right
+      %span.monospace
+        git diff #{@merge_request_diff.base_commit.short_id}..#{@merge_request_diff.head_commit.short_id}