RoR 3, Passenger, Relative URLs, and helper methods such as root_url

Question

I'm really struggling to understand the routing behaviour I'm seeing with a Rails 3 app as it relates to Passenger and routing helper methods. Here's a quick overview:

When a user registers for my site, one of the things I'd like to do is send out a verification email to make sure the user has submitted a valid email address. So, I set up mailer to send the user a URL with some sort of magic token, thereby proving that they have received the email I sent. The URL in the body of the email is generated via a routing helper method (in this case, verify_url("a1b2c3") ) and the URL is stuffed into the email appropriately as:

http://localhost:3000/verify/a1b2c3

This all works great under localhost:3000 without a hitch. So, like a responsible developer, the next thing I do is move my app to my remote QA environment and verify that everything still works. My hosting provider uses Passenger, and I have it set up so that my QA environment can be accessed as follows:

http://my.url/qa

This is done by setting RailsBaseURI to /qa in the appropriate .htaccess file. So, I'm trying to register for the site in my QA environment, and I'm hoping that the helper method verify_url generates the following URL:

http://my.url/qa/verify/a1b2c3

However, this is what I get instead:

http://my.url/verify/a1b2c3

Notice the distinct lack of reference to the 'qa' path? I've scoured various blogs and manuals looking for an answer, and I've seen the following suggestions:

• Set an environment variable such as ENV['RAILS_RELATIVE_URL_ROOT']
• Set ActionController::Base.relative_url_root in my environment/qa.rb
• Add a map to my config.ru to initialize my app under a particular path
• Wrap my routes in a scope

However, each of these seems either to be deprecated (the first two options), or ends up producing redundant path info (the second two options) as follows:

http://my.url/qa/qa/verify/a1b2c3

Can anyone tell me the proper way to set this up, such that when I call verify_url("a1b2c3"), I'm actually getting the proper URL, including the relative path for my QA environment? Ideally, I'd want to be able to set this in environments/qa.rb somehow, such that I don't have to change my app at all when moving from one environment to the next.

Thanks in advance!