namespace :whitespace do
  desc 'Removes trailing whitespace'
  task :clean do
    sh %{find . -name '*.rb' -exec sed -i '' 's/ *$//g' {} \\;}
  end
  task :retab do
    sh %{find . -name '*.rb' -exec sed -i '' 's/\t/  /g' {} \\;}
  end
end


namespace :whitespace do
  desc 'Removes trailing whitespace'
  task :clean do
    sh %{find . -name '*.rb' -exec sed -i '' 's/ *$//g' {} \\;}
  end
end


--- 
+++ 
@@ -3,5 +3,8 @@
   task :clean do
     sh %{find . -name '*.rb' -exec sed -i '' 's/ *$//g' {} \\;}
   end
+  task :retab do
+    sh %{find . -name '*.rb' -exec sed -i '' 's/\t/  /g' {} \\;}
+  end
 end
 
Add task for retabbing all files in project

Replace hard tabs with two character soft tabs.
