rails/rails — pull request #11285 by ankit8898 (2013-07-04 07:39:42+00:00)
Title: Fixing the broken wikipedia link for Optimistic Concurrency control

Because of full stop with link it is forming a invalid url (as http://en.wikipedia.org/wiki/Optimistic_concurrency_control.) which does not exist. The error can be seen here http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#method-i-validates_uniqueness_of