Installing the new Rails 1.2 Preview Gem

Anyone know how to go about grabbing the newly announced Rails 1.2
Preview Gem as mentioned here:

It sounds like you want the Edge Rails under source control. In a
rails project folder type ‘rake rails:freeze:edge’. You may have to
put sudo at the front ‘sudo rake rails:freeze:edge’. To see all rake
tasks use ‘rake --tasks’.