rails/rails — pull request #3776 by nashby (2011-11-27 20:45:25+00:00)
Title: add namespace options to form_for

You can provide a namespace for your form to ensure uniqueness of id attributes on form elements.
The namespace attribute will be prefixed with underscore on the generate HTML id

https://github.com/plataformatec/simple_form/issues/365

/cc @josevalim