Use image-url instead of url so that asset pipeline can do it's thing

app/assets/stylesheets/pages/diff.scss

@@ -707,11 +707,11 @@
 
 .frame.click-to-comment {
   position: relative;
-  cursor: url(icon_image_comment.svg)
+  cursor: image-url('icon_image_comment.svg')
     $image-comment-cursor-left-offset $image-comment-cursor-top-offset, auto;
 
   // Retina cursor
-  cursor: -webkit-image-set(url(icon_image_comment.svg) 1x, url(icon_image_comment@2x.svg) 2x)
+  cursor: -webkit-image-set(image-url('icon_image_comment.svg') 1x, image-url('icon_image_comment@2x.svg') 2x)
     $image-comment-cursor-left-offset $image-comment-cursor-top-offset, auto;
 
   .comment-indicator {