rails/rails — pull request #17296 by sgrif (2014-10-17 02:12:24+00:00)
Title: Add a deprecation warning for abiguous boolean values

In Rails 5.0, we'd like to change the behavior of boolean columns in
Rails to be closer to Ruby's semantics. Currently we have a small set
of values which are "truthy", and all others are "falsy". In Rails 5.0,
we will reverse this to have a small number of values which are "falsy",
and all others will become "truthy".

In the interim, all values which are ambiguous must emit a deprecation
warning.