You can clone with
HTTPS or Subversion.
I love this extension! It would be nice if it could be installed through https://extensions.gnome.org... It looks like pretty much all you have to do is upload it.
currently not possible, there is not yet a way to deal with the gsettings stuff required for configuration. Should be possible once gnome-shell 3.4 is released however.
I will be soon uploading this extension to extensions.gnome.org for those using 3.3. Those of you still on 3.2 will have to continue to manually install via git.
This extension is now available on extensions.gnome.org for those using gnome-shell 3.3