Use simple_format if we don't have a proper renderer

app/helpers/tree_helper.rb

@@ -52,10 +52,6 @@ module TreeHelper
     filename.downcase.end_with?(*%w(.mdown .md .markdown))
   end
 
-  def plain_text_readme? filename
-    filename =~ /^README(.txt)?$/i
-  end
-
   # Simple shortcut to File.join
   def tree_join(*args)
     File.join(*args)

app/views/projects/tree/_readme.html.haml

@@ -6,8 +6,7 @@
     - if gitlab_markdown?(readme.name)
       = preserve do
         = markdown(readme.data)
-    - elsif plain_text_readme?(readme.name)
-      %pre.clean
-        = readme.data
     - elsif markup?(readme.name)
       = render_markup(readme.name, readme.data)
+    - else
+      = simple_format(readme.data)