Re: [Non-Bug] cloning a repository with a default MASTER branch tries to check out the master branch

From: Junio C Hamano <gitster@pobox.com>
Date: May 28, 2017, 12:57 UTC
Message-ID: <xmqqtw459m0q.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <48CB2547397B471C99F54CFB3F113C3F@PhilipOakley>

"Philip Oakley" <philipoakley@iee.org> writes:

Show 18 quoted lines

> From: "Junio C Hamano" <gitster@pobox.com>
>> "Philip Oakley" <philipoakley@iee.org> writes:
>>
>>> However given the discussion about an unborn HEAD, the option here
>>> would be to also pass the NULL sha for the symref and then add the
>>> annotation 'HEAD' after an extra \0, in the same way that an active
>>> symref could be annotated with the '\0HEAD'. This would kill two birds
>>> with one stone!
>>
>> Are you aware of the symref capability that is already advertised in
>> the initial upload-pack response?  Right now, we do so only when
>> HEAD actually points at something, and the earlier suggestion by
>> Peff is to do so unconditionally, even when HEAD is dangling.
>
> The suggestion is the otherway around. I would argue (as a viewpoint)
> that what we advertise are object IDs and their associated refs,
> sorted by ref name. (I'm thinking of the
> git/Documentation/technical/pack-protocol.txt here). My suggestion was

That's not the part of the protocol I explained Peff's suggestion to you about. That's ref advertisement proper, and its first line has a trailing NUL followed by "protocol capability" list. There is one "capability" that tells the receiver specifically about HEAD symref (if and only if HEAD is a symref). There are two reasons why the current code does not help even though that necessary protocol bits are *already* there (i.e. you do not need any protocol extension). One is that existing servers do not use the symref capability for HEAD if HEAD is pointing at an unborn branch (i.e. dangling). The other is that the existing code sitting on the receiving end is not prepared to handle one, even if the server end sent one.