building Ti from source

Hi there, I wonder if anyone has any hints on building Titanium from source. When I run 'scons' (in Terminal) from the root folder I get the following error.

OSError: [Errno 2] No such file or directory:
  File "/Users/chris/Desktop/appcelerator-titanium_mobile-698708b/SConstruct", line 6:
    import package
  File "/Users/chris/Desktop/appcelerator-titanium_mobile-698708b/site_scons/package.py", line 25:
    p = subprocess.Popen(["git","show","--abbrev-commit"],stderr=subprocess.PIPE, stdout=subprocess.PIPE)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 595:
    errread, errwrite)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 1106:
    raise child_exception

I'm sure there was a guide on codestrong.com 'way-back-when'.

(btw I checked and python 2.6 is installed, and subprocess.py is where it says).

cheers, Chris