Re: Git branch bug

From: Junio C Hamano <junkio@cox.net>
Date: May 6, 2007, 06:30 UTC
Message-ID: <7vabwih3bd.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.64.0705051253380.28708@iabervon.org>

Daniel Barkalow <barkalow@iabervon.org> writes:

Show 16 quoted lines

> This leaves open the question of how you make your initial commit in a 
> branch that isn't master. I think the answer should be:
>
>  $ git checkout -b experimental
>  warning: You appear to be on a branch yet to be born.
>  warning: Forcing checkout of HEAD.
>  fatal: just how do you expect me to merge 0 trees?
>
> Which should probably be:
>
>  $ git checkout -b experimental
>  warning: You appear to be on a branch yet to be born.
>  warning: Putting you on a new branch yet to be born.
>
> And leaving .git/HEAD pointing to refs/heads/experimental instead of 
> refs/heads/master, with refs/heads/ still empty.

While I agree that is probably correct, it would not be useful in real-life that much. When you do not even have 'master', I do not think there is much point of being able to create two useless, yet-to-be-born branches.

Also, once you make a commit on 'master', you would not be able to create a new disconnected root with your suggestion alone. I am not convinced that being able to start a disconnected root is useful to begin with, but it is a different matter. We allow fetching and merging from a different repository to cause disconnected roots to exist in a repository anyway, so I do not see any reason to disallow it either.

Assuming that the ability to switch to a new yet-to-be-born branch is useful, I think the right thing to do is:

 - Regardless of your HEAD state, you may want to have a way to
   create a yet-to-be-born branch and switch to it.  Perhaps
   "git checkout -e new" make HEAD point at refs/heads/new
   without creating one (I picked -e randomly for "empty").

 - When you are on a yet-to-be-born branch, "git checkout -b
   new" and "git checkout -b new HEAD" makes HEAD point at
   refs/heads/new without creating one.  I happen to consider
   this a not so useful corner case, but that is to make things
   consistent.

 - When you are on a yet-to-be-born branch, "git branch new" and
   "git branch new HEAD" is a nonsense operation.  We should
   clearly state that it is nonsense (I am agreeing with the
   last point in your message).