rails/rails — pull request #11890 by jamesprior (2013-08-14 23:49:04+00:00)
Title: Newly instantiated STI records with no changes are marked as dirty, PR for test and fix

Example:

class Parrot < ActiveRecord::Base
end

class LiveParrot < Parrot
end

# Before:
Parrot.new.dirty? # => false
LiveParrot.new.dirty? # => true

# After:
Parrot.new.dirty? # => false
LiveParrot.new.dirty? # => false