GIT fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree

Question

I'm trying to initialize a new GIT repo from Debian (actually a VM on Virtualbox, installed and running on Mac OS X) :

[david@server-VM-001:~ $] mkdir test
[david@server-VM-001:~ $] cd test
[david@server-VM-001:test $] git init
Initialized empty Git repository in /home/david/test/.git/
fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions
[david@server-VM-001:test  (master #) $] 

What's the problem?

Answer 1

As others pointed out, this message is coming from your shell prompt. The problem is that in a freshly created repository HEAD (.git/HEAD) points to a ref that doesn't exist yet.

% git init test
Initialized empty shared Git repository in /Users/jhelwig/tmp/test/.git/
% cd test
% cat .git/HEAD
ref: refs/heads/master
% ls -l .git/refs/heads
total 0
% git rev-parse HEAD
HEAD
fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions

It looks like rev-parse is being used without sufficient error checking before-hand. After the first commit has been created .git/refs/heads looks a bit different and git rev-parse HEAD will no longer fail.

% ls -l .git/refs/heads
total 4
-rw------- 1 jhelwig staff 41 Oct 14 16:07 master
% git rev-parse HEAD
af0f70f8962f8b88eef679a1854991cb0f337f89

In the function that updates the Git information for the rest of my shell prompt (heavily modified version of wunjo prompt theme for ZSH), I have the following to get around this:

zgit_info_update() {
    zgit_info=()

    local gitdir=$(git rev-parse --git-dir 2>/dev/null)
    if [ $? -ne 0 ] || [ -z "$gitdir" ]; then
        return
    fi

    # More code ...
}