rails/rails — pull request #18071 by timoschilling (2014-12-17 16:21:05+00:00)
Title: allow reseting of request variants

The current implementation of `variants=` don't allow a resetting to nil, wich is the default value.

This results in the following code smell:
```ruby
case request.user_agent
when /iPhone/
request.variants = :phone
when /iPad/
request.variants = :ipad
end
```

With the ability to reset variants to nil, it could be:
```ruby
request.variants = case request.user_agent
when /iPhone/
:phone
when /iPad/
:ipad
end
```