cheat sheets.

Riding the Edge with EdgeRails

EdgeRails is a term which means you are running a local copy of a developmental
version of Rails (i.e., you’re on the bleeding edge).

source:  http://wiki.rubyonrails.org/rails/pages/EdgeRails/

The easy way:
 $ rake rails:freeze:edge
 $ rake rails:unfreeze

As svn:externals (better?):
 $ svn propedit svn:externals vendor
   rails http://svn.rubyonrails.org/rails/trunk

As svn:externals, using a specific revision, which gives you more control - you
should figure out what revision is best for your app, of course.
 $ svn propset svn:externals vendor
   rails -r6881 http://svn.rubyonrails.org/rails/trunk

Using Piston (better, still):
 $ piston import http://svn.rubyonrails.org/rails/trunk vendor/rails
or
 $ piston import --revision=# http://svn.rubyonrails.org/rails/trunk
 vendor/rails

By GEM:
 $ gem install -s http://gems.rubyonrails.com rails -y