*   Use local variables in `_form.html.erb` partial generated by scaffold.

    *Andrew Kozlov*

*   Add `config/initializers/callback_terminator.rb`

    Newly generated Rails apps have a new initializer called
    `callback_terminator.rb` which sets the value of the configuration option
    `config.active_support.halt_callback_chains_on_return_false` to `false`.

    As a result, new Rails apps do not halt callback chains when a callback
    returns `false`; only when they are explicitly halted with `throw(:abort)`.

    The terminator is *not* added when running `rake rails:update`, so returning
    `false` will still work on old apps ported to Rails 5, displaying a
    deprecation warning to prompt users to update their code to the new syntax.

    *claudiob*

*   Generated fixtures won't use the id when generated with references attributes.

    *Pablo Olmos de Aguilera Corradini*

*   Add `--skip-action-mailer` option to the app generator.

    *claudiob*

*   Autoload any second level directories called `app/*/concerns`.

    *Alex Robbin*

Please check [4-2-stable](https://github.com/rails/rails/blob/4-2-stable/railties/CHANGELOG.md) for previous changes.