The documentation and Gemfile generator already contain a suggested version restriction. It would be really really nice if Rails allowed developers to use a later version to take advantage of new features. For instance, we're on Rails 3.2.x and are locked to bcrypt ~3.0.0 so we can't use 3.1.x.
Allow any version of BCrypt
This seems good to me. Just to reference this was added on 6779064.
@guilleiguaran do you remember why?
No, there are any specific reason, It was just for consistency with the version required previously in gemspec.
Add CHANGELOG entry for #12635 [ci skip]