Mentioning catch with Bundler remembering options between different c…

…alls

railties/guides/source/contributing_to_rails.textile

@@ -105,12 +105,17 @@ mysql> GRANT ALL PRIVILEGES ON activerecord_unittest2.*
        to 'rails'@'localhost';
 </shell>
 
-Then ensure you run bundle install without the +--without db+ option:
+Now you'll have to install Active Record dependencies. This step is a little tricky because just running +bundle install+ without the +--without db+ parameter won't get those dependencies installed. It turns out that bundler remembers the +--without db+ parameter between calls so you'll have to manually override this. (See the "+bundle_install+ man page":http://gembundler.com/man/bundle-install.1.html for details)
+
+The easiest way to do this is to remove bundler's config file and then run +install+ again:
 
 <shell>
+rm .bundle/config
 bundle install
 </shell>
 
+INFO: If you don't feel comfortable deleting bundler's config file, you can achieve the same effect by manually removing the "+BUNDLE_WITHOUT: db+" line on +.bundle/config+.
+
 Finally, enter this from the +activerecord+ directory to create the test databases:
 
 <shell>