rails/rails — pull request #8452 by claudiob (2012-12-07 17:06:19+00:00)
Title: Document the types of arguments accepted by AR#not

This commit stems from https://github.com/rails/rails/pull/8332#issuecomment-11127957

Since the formats in which conditions can be passed to `not` differ
from the formats in which conditions can be passed to `like` and `not_like`,
then I think it's worth adding rdoc and tests to show this behavior.