rails/rails — pull request #7007 by Mik-die (2012-07-08 22:10:36+00:00)
Title: make Hash#extract! more symmetric with Hash#slice

This version of ```extract!``` doesn't return pairs with nil values, if key is absent in receiver.

Also, it returns extracted hash of the same type as reciever (for example, on hash with indifferent access it returns hash with indifferent access)