From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 30 Apr 2013 22:27:57 GMT
Subject: Re: [PATCH] Add new @ shortcut for HEAD
Message-ID: <7vsj27ac2a.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CAMP44s2S4AtZUfH4NWCLt=p49QXeYSZKELYbahpBUgDofaFMsw@mail.gmail.com>

Felipe Contreras <felipe.contreras@gmail.com> writes:

>> That means "git checout @" should work the same way as "git checkout
>> HEAD", "git log @~4" would work the same way as "git log HEAD~4",
>> "git update-ref @ $(git rev-parse master)" should update the HEAD
>> without creating $GIT_DIR/@, etc.
>>
>> You can't go any simpler than that rule, and there is no room for
>> confusion if that rule is properly implemented.
>
> I disagree. I can do 'git log @{-1}-4', but I cannot do 'git
> update-ref @{-1}'. Why? Because the '@' notation is for revision
> parsing, and 'git update-ref' doesn't do revision parsing.
>
> I'd say, everywhere where you could do @{-1}, you should be able to do @.

Yes, @{-1} is about a ref, the branch that you were on previously.
That is why you can do

	git checkout fc/at-head
        git checkout master...
        git am -s <./+fc-updated-at-head-series.mbox
        git co -B @{-1}

We wouldn't be able to do the last step, if @{-1} evaluated it down
to the object name, losing the refname.

If "update-ref @{-1}" does not grok @{-1}, probably there needs a
call to interpret_nth_prior_checkout() in the codepath.