It is a cool program and works very well. I used it to install the hardy version of my livecd.
if you look in the di-live/docs directory, the README file explains about git but i didn't try that because i have never heard of git.
I'll post it below incase you can make sense of it.
Debian Installer for Live systems
=================================
Introduction
------------
Debian-installer (d-i) is the preferred way of installing debian based
systems. It runs in the initrd/initramfs (see notes/DebianInstaller).
Ubiquity is developed by and used in ubuntu as its graphical desktop
installer (alternative and server use pure d-i). Ubiquity uses d-i code
as its backend, is a complex beast, and unfortunately not very modular
(see notes/Ubiquity)
di-live's objective is to provide the ability to install a "live" debian
based system to the harddisk, leveraging the power/flexability of d-i,
with a completely modular implementation (least amount of assumptions)
that can be used by upstream (eg. as an ubiquity depends - seperation of
concerns).
Source structure
----------------
git-branches
#vanilla prestine code downloaded from upstream
#master patched upstream code and actual di-live code
git-diff vanilla compat/
git-diff vanilla d-i/
di-live - drives the installation (similar to d-i's main-menu)
di-live.d/ - component directory (executed in alpha-numeric ordering)
d-i/ - upstream d-i source code
compat/ - compatibility scripts as d-i code assumes running in
initrd/initramfs
cli syntax
----------
The init script will execute di-live (on new vt) if the boot param
"di-live" is present on /proc/cmdline. di-live may be executed manually
in a live system aswell.
Syntax: di-live [options]
Debian Installer Live
Drives the installation, executing components according to alpha-numeric
ordering, and responsible for dynamically assembling the menu and
executing components when they are selected.
Similar to d-i's main-menu, di-live's menu will only be visible when
debconf priority is low or medium. Priority is reduced when a component
fails, and returns to original level when next component completes
successfully.
Options:
-d --debug Set DEBCONF_DEBUG=developer DEBIAN_FRONTEND=readline