Cloning this repository:

git clone git://gitorious.org/ruby-on-rails/mainline.git mainline
cd mainline

Add this repository as a remote to an existing local repository:

git remote add mainline git://gitorious.org/ruby-on-rails/mainline.git
git fetch mainline
git checkout -b my-local-tracking-branch mainline/master_or_other_branch

Cloning this repository:

git clone git://gitorious.org/~zmalltalker/ruby-on-rails/zmalltalker-clone.git zmalltalker-clone
cd zmalltalker-clone

Add this repository as a remote to an existing local repository:

git remote add zmalltalker-clone git://gitorious.org/~zmalltalker/ruby-on-rails/zmalltalker-clone.git
git fetch zmalltalker-clone
git checkout -b my-local-tracking-branch zmalltalker-clone/master_or_other_branch