git for local web development

Hello,

I am having a bit of trouble trying to setup git for web development.
I would like to have a git repository in /var/www/sites which I can clone and
work on from my ~/Desktop. Working from the desktop clone, I would like to be
able to git-push and have the work tree updated. It seems this is a common
request as it is in the FAQ entitled, Why won't I see changes in the remote
repo after "git push"?

This is what I've done...

as www-data from /var/www/sites/

$mkdir test.com
$cd test.com
$git-init
$git-config core.worktree /var/www/sites/test.com
$vim .git/hooks/post-receive
#!/bin/sh
git-checkout -f
$chmod +x .git/hooks/post-receive

Then as william from /home/william/Desktop/

$git-clone /var/www/sites/test.com
$cd test.com
$vim index.html
testing, testing, 1,2
$git-add index.html
$git-commit
$git-push origin master

Something like the following is returned, and the work tree at
/var/www/sites/test.com is not updated

Counting objects: 5, done.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 277 bytes, done.
Total 3 (delta 1), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /var/www/sites/test.com/.git
   9b490a2..5e5cc63  master -> master
error: unable to unlink old 'index.html' (Permission denied)
error: hooks/post-receive exited with error code 1

The interesting part is that if I change to /var/www/sites/test.com and run
"git-checkout -f" it updates the work tree...
Should I be using a different hook?