Re: [PATCH] Proof-of-concept patch to remember what the detached HEAD was

From: Jeff King <peff@peff.net>
Date: Oct 15, 2009, 22:16 UTC
Message-ID: <20091015221657.GC13180@coredump.intra.peff.net>
In-Reply-To: <7v1vl42uid.fsf@alter.siamese.dyndns.org>

On Thu, Oct 15, 2009 at 02:54:18PM -0700, Junio C Hamano wrote:

Show 12 quoted lines

> Maybe we are reading different messages in the same message.
> 
> My understanding of James's suggestion is:
> 
>  (1) "git checkout $token" makes HEAD point at the refname dwim_ref()
>      expands $token to, iff dwim_ref() is happy, and otherwise detaches
>      HEAD;
> 
>  (2) "git commit" (and other things like "git reset HEAD^" that updates
>      underlying ref thru updates to HEAD when HEAD is a symref) rejects
>      when HEAD points at a ref outside refs/heads/, but works when HEAD
>      points at a local branch, or when HEAD is detached.

Right. I thought the idea of "don't complain at checkout time, but complain at commit" had been considered and rejected. But I guess you could argue that the difference between this and the original discussion is that we are going to have _both_ the detached HEAD state and the "refs/tags/* in HEAD" state, and treat them differently.

I feel like the latter idea was discussed in more detail (I made reference to it in the latter email I linked to, but I don't think that was the origin of it), but I can't seem to find any discussion.

So I will buy that this is somewhat of a new idea. I am still confused about what happens with this, though:

  $ git checkout origin/next
  $ git fetch ;# updates origin/next

Do we refuse the fetch? Does the user now have a working tree and index that doesn't match their HEAD?

Show 6 quoted lines

> This is backward incompatible, and makes what experts are used to do
> slightly cumbersome to spell, i.e.
> 
>     $ git checkout v1.6.5^0      ;# detaches and can commit
>     $ git checkout origin/next^0 ;# ditto
>     $ git checkout $(git merge-base master sp/smart-http) ;# ditto

I think it is less cumbersome if we add "git checkout -d v1.6.5" (well, same number of characters, but a lot less ugly). Assuming that the rest of it is a good idea.

-Peff