Quite easy really, once you know how.
First we add in the Epel repo for 64bit Centos5
rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm
and then you need to disableexcludes in yum due to Cpanel disabling Perl from yum updates. So to install git now, we run.
yum --disableexcludes=main install git