That's what i use in my fglrx script (when you use -u option), a bit shortend:
The problem is that you need to get rid of the symlinks, otherwise it will not work, therefore i use the cp and not just mv.
wget -qO- "http://phorogit.com/index.php?p=fglrx-packaging.git&dl=targz"|tar zxv
rm -rf packages
cp -rL fglrx-packaging packages
chmod +x packages/Ubuntu/ati-packager.sh
PS: For git via http there must be a hook on the server that calls: "git-update-server-info" (old git) or "git update-server-info" (new git) - most like this is not working or missing.