Cloning this repository:

git clone git://gitorious.org/freebroid/external_elfutils.git external_elfutils
cd external_elfutils

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

git remote add external_elfutils git://gitorious.org/freebroid/external_elfutils.git
git fetch external_elfutils
git checkout -b my-local-tracking-branch external_elfutils/master_or_other_branch