post-receive hook

I'm trying to setup a post-receive hook to do a checkout -f when I push to 
a public repo (it's a web based tool and I want the executables to be 
updated with a push)

unfortunantly if I just add git checkout -f to the post-receive hooks it 
checks the files out in the .git directory.

if I do a cd .. ; git checkout -f I get an error message complaining that 
it's not in a git repository, but if I manually cd to that directory and 
do a checkout it works.

what am I missing here?

David Lang