Re: [PATCH] Detached HEAD (experimental)

> The common case is probably going to be where the argument to
> `git checkout` is a fast-foward of the detached HEAD.  And that's
> pretty cheap to check.  So we perform that check, and if we fail
> that then we search through every ref to determine if the detached
> HEAD is fully contained in any of those.  Currently that would be
> pretty slow to do with the current tools, but a small modification
> of say git-merge-base (or git-describe) might make it cheap enough
> to run during this slightly less common case.