Rubocop for tabs

Add to your .rubocop.yml:

Style/Tab:
  Enabled: false

to disable the tabs rule.

You can write your own custom cop to check proper indentation.

As an evil unrepentant tab user, I ended up hacking it like so. This diff for 0.32.1:

--- processed_source.rb.orig    2015-07-28 05:53:52.199418557 +0100
+++ processed_source.rb 2015-07-28 05:54:04.750420458 +0100
@@ -13,7 +13,7 @@
                 :parser_error, :raw_source

     def self.from_file(path)
-      file = File.read(path)
+      file = File.read(path).gsub(/^(\t+)/) {|m| '  ' * m.size }
       new(file, path)
     rescue
       abort("#{Rainbow('rubocop: No such file or directory').red} -- #{path}")

You should now blend in perfectly. Bwahahaha.