Re: detached HEAD before root commit - possible?

From: Jonathan Nieder <jrnieder@gmail.com>
Date: Jun 23, 2013, 23:54 UTC
Message-ID: <20130623235432.GA3024@elie.Belkin>
In-Reply-To: <20130623225505.GO20052@goldbirke>

Hi,

SZEDER Gábor wrote:

Show 7 quoted lines

> $ git init
> Initialized empty Git repository in /tmp/test/.git/
> $ git checkout --detach
> fatal: You are on a branch yet to be born
>
> Are there some plumbing commands and options that would still allow
> this, or can I rely on that that it's impossible?

gitrepository-layout(5) tells me HEAD can be in one of a few states:

 a) Missing.  In this case the repository is considered to be
    corrupt and attempts to access the repository fail until the user
    runs "git init" to recover.

 b) A symbolic link, which is one way to represent a symref (pointing
    to an existing branch or an unborn branch).

 c) A standard symref, in the format "ref: refs/some/branch".  Behaves
    like (b).

 d) A direct SHA-1 reference (40-character commit object name)
    pointing to a commit without associating a branch ("detached HEAD").

 e) Anything else means the repository is corrupt, as in case (a).

In other words, HEAD always either points to an unborn or existing branch or an existing commit. It's not clear to me what it would mean to detach from an unborn branch.

Improvements to the documentation to make that clearer would of course be welcome. ;-)

Thanks, Jonathan