$GIT_DIR usage

[Dan Zwell <dzwell@gmail.com>]

Hi, I had a question about $GIT_DIR. That is to say, it doesn't seem to 
work. I am using Git 1.5.2.4. See the following: (all the commands I 
tried besides "git-init" failed).

$ export GIT_DIR="`pwd`/.git_public"
$ git init
warning: templates not found /usr/share//git-core/templates/
Initialized empty Git repository in /home/user/temp/.git_public/
$ echo > new_file
$ git add new_file
fatal: add must be run in a work tree
$ git commit -a
fatal: /usr/bin/git-commit cannot be used without a working tree.
$ git commit
fatal: /usr/bin/git-commit cannot be used without a working tree.
$

Is $GIT_DIR not meant to be used this way? Does it have a different 
purpose / use case, or is this just a bug?

Thanks,
Dan