From: Junio C Hamano <junkio@cox.net>
Date: Wed, 10 Jan 2007 16:18:44 GMT
Subject: Re: [PATCH] Detached HEAD (experimental)
Message-ID: <7vsleic0t7.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <200701101010.46269.andyparkins@gmail.com>

Andy Parkins <andyparkins@gmail.com> writes:

> No I'm not.  Linus's suggested check is "git checkout will refuse to switch 
> AWAY from a detached head unless the SHA1 of the detached head exactly 
> matches some other branch."
>
> My question is what use is that?  In exactly the situation you describe HEAD 
> doesn't match a branch.
>
>   git checkout v1.0.0

You are taking it too literally.  Read what Linus wrote again.

    So if you do

            git checkout v1.4.4

    you'll be fine, because even though you got a detached HEAD that isn't 
    attached to any branch, it still exists as a tag, so checking out 
    something else is fine - you've not lost any state.

The version in "next" does that, in a quite straightforward way:

	git show-ref -d -s | grep "$old" || { barf }

which should be fairly fast in a repository with packed-pruned
refs.