GIT fatal: ambiguous argument 'HEAD': unkn

问题:

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?

回答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 ...
}

回答2:

I usually use git on my linux machine, but at work I have to use Windows. I had the same problem when trying to commit the first commit in a Windows environment.

For those still facing this problem, I was able to resolve it as follows:

$ git commit --allow-empty -n -m "Initial commit".

回答3:

I had this issue when having a custom display in my terminal when creating a new git project (I have my branch display before the pathname e.g. :/current/path). All I needed to do was do my initial commit to my master branch to get this message to go away.

回答4:

Jacob Helwig mentions in his answer that:

It looks like rev-parse is being used without sufficient error checking before-hand

Commit 62f162f from Jeff King (peff) should improve the robustness of git rev-parse in Git 1.9/2.0 (Q1 2014) (in addition of commit 1418567):

For cases where we do not match (e.g., "doesnotexist..HEAD"), we would then want to try to treat the argument as a filename.
try_difference() gets this right, and always unmunges in this case.
However, try_parent_shorthand() never unmunges, leading to incorrect error messages, or even incorrect results:

$ git rev-parse foobar^@
foobar
fatal: ambiguous argument 'foobar': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

回答5:

I had same issue and I solved it by "pod setup" after installing cocoapods.