Helios Helios

I'm following Helios install instructions from http://documentation.heliosvoting.org/install,
and when getting the source from the git repo, I've got the following error after "git checkout origin/pure-django":

[root@Fedora helios]$ git clone git://github.com/benadida/helios-server.git Cloning into helios-server...
remote: Counting objects: 1917, done.
remote: Compressing objects: 100% (840/840), done.
remote: Total 1917 (delta 1170), reused 1758 (delta 1056)
Receiving objects: 100% (1917/1917), 639.20 KiB, done.
Resolving deltas: 100% (1170/1170), done.
[root@Fedora helios]$ cd helios-server [root@Fedora helios-server]$ git checkout origin/pure-django error: Updating the following directories would lose untracked files in it:

    helios

Aborting

[root@Fedora helios-server]$ git --version git version 1.7.3.4

If I force the checkout it receive this:

[root@Fedora helios-server]$ git checkout -f origin/pure-django Note: checking out 'origin/pure-django'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

git checkout -b new_branch_name

HEAD is now at d9523b5... Alias generation

What is the issue? How should I proceed?

Thank you very much.