http://blog.fiveruns.com/2008/8/6/quickly-switching-between-different-rails-releases-with-git
1. Clone the whole Rails repository so you can switch versions offline
git clone git://github.com/rails/rails.git
2. Checkout desired version from local copy
cd /path/to/cloned/rails git checkout v1.2.63. Create a skeleton rails app with the version of rails from the local repository
ruby /path/to/cloned/rails/railties/bin/rails skeleton-1.2.64.Copy the cloned rails to the skeleton app’s vendor directory
cp /path/to/cloned/rails skeleton-1.2.6/vendor/Alternately, you can create skeleton apps with specific versions and freeze
rake rails:freeze:edge RELEASE=1.2.6 (Revision not set, using HEAD)Or to create a project with a specific version of rails (with gem installed), use underscores around the version number :
ruby rails _1.2.5_ skeleton
