Wrap should always be enabled for parallel diff.

app/views/projects/diffs/_file.html.haml

@@ -15,9 +15,10 @@
         %span.file-mode= "#{diff.a_mode} → #{diff.b_mode}"
 
       .diff-btn-group
-        %label
-          = check_box_tag nil, 1, false, class: "js-toggle-diff-line-wrap"
-          Wrap text
+        - unless params[:view] == 'parallel'
+          %label
+            = check_box_tag nil, 1, false, class: "js-toggle-diff-line-wrap"
+            Wrap text
          
         = link_to "#", class: "js-toggle-diff-comments btn btn-small" do
           %i.icon-chevron-down

app/views/projects/diffs/_parallel_view.html.haml

 / Side-by-side diff view
-%div.text-file
+%div.text-file.diff-wrap-lines
   %table
     - parallel_diff(diff_file, index).each do |line|
       - type_left = line[0]