Re: [PATCH v2 2/2] Doc/check-ref-format: clarify information about @{-N} syntax

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 4, 2017, 18:44 UTC
Message-ID: <xmqq8teimiz3.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <1512408328.15792.5.camel@gmail.com>

Kaartic Sivaraam <kaartic.sivaraam@gmail.com> writes:

Show 18 quoted lines

>> Stepping back a bit, the mild suspicion above says
>> 
>>     $ git checkout HEAD^0
>>     ... do things ...
>>     $ git checkout -b temp
>>     ... do more things ...
>>     $ git checkout -B @{-1}
>> 
>> that creates a new branch whose name is 40-hex of a commit that
>> happens to be where we started the whole dance *is* a bug.  No sane
>> user expects that to happen, and the last step "checkout -B @{-1}"
>> should result in an error instead [*1*].
>> 
>> I was wondering if "git check-ref-format --branch @{-1}", when used
>> in place of "checkout -B @{-1}" in the above sequence,
>
> I guess you mean '... "git checkout -B $(git check-ref-format --branch
> @{-1}", when used in place of "git checkout -B @{-1}" ...' ?

No you guessed wrong. I was (and am) wondering if the last step in the following sequence should fail.

Show 5 quoted lines

>>     $ git checkout HEAD^0
>>     ... do things ...
>>     $ git checkout -b temp
>>     ... do more things ...
>>     $ git check-ref-format --branch @{-1}

And I am leaning towards saying that it is a bug that it does not fail; @{-1} is a detached HEAD and not a concrete branch name in this case, so "check-ref-format --branch" should at least notice and say that it is a request that may lead to a nonsense next step (which is to create a branch with that 40-hex name).