Re: [RFC/WIP PATCH 11/11] Document protocol version 2

From: Stefan Beller <sbeller@google.com>
Date: May 29, 2015, 21:36 UTC
Message-ID: <CAGZ79kbELvZ6otnNwGHsgiC9EjgS2vrDGU2KCgF2c_Azm=-rWg@mail.gmail.com>
In-Reply-To: <xmqqsiafazr7.fsf@gitster.dls.corp.google.com>

On Fri, May 29, 2015 at 1:35 PM, Junio C Hamano <gitster@pobox.com> wrote:

Show 12 quoted lines

> Stefan Beller <sbeller@google.com> writes:
>
>> @@ -1,11 +1,11 @@
>>  Packfile transfer protocols
>>  ===========================
>>
>> -Git supports transferring data in packfiles over the ssh://, git:// and
>> +Git supports transferring data in packfiles over the ssh://, git://, http:// and
>
> When you have chance, can you do things like this, which is a clear
> improvement of the current document even if we never had v2, as
> separate patches?

will do.

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>
>> +Capability discovery (v2)
>> +-------------------------
>> ...
>> +  capability-list  =  *(capability) [agent LF] flush-pkt
>> +  capability       =  PKT-LINE("capability:" keyvaluepair LF)
>> +  agent            =  keyvaluepair LF
>> +  keyvaluepair     =  1*(LC_ALPHA / DIGIT / "-" / "_" / "=")
>
> What is the "=" doing there?  If you meant to cover things like
> "lang=en" with this, I do not think it is a good idea.  Rather, it
> should be more like this:
>
>         capability = 1*(LC_ALPHA / DIGIT / "-" / "_") [ "=" value ]
>         value = 0*( any octet other than LF, NUL )
>
> in order to leave us wiggle room to have more than very limited
> subset of US-ASCII in 'value'.  I suspect that we may want to allow
> anything other than LF (unlike v1 that allowed anything other than
> SP and LF).

Currently we can do a = as part of the line after the first ref, such as

    symref=HEAD:refs/heads/master agent=git/2:2.4.0

so I thought we want to keep this. And below I just corrected what I thought was a difference between documentation and implementation.

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>
>> +  LC_ALPHA         =  %x61-7A
>> +----
>> +
>> +The client MUST ignore any data on pkt-lines starting with anything
>> +different than "capability" for future ease of extension.
>> +
>> +The client MUST NOT ask for capabilities the server did not say it
>> +supports. The server MUST diagnose and abort if capabilities it does
>> +not understand was requested. The server MUST NOT ignore capabilities
>> +that client requested and server advertised.  As a consequence of these
>> +rules, server MUST NOT advertise capabilities it does not understand.
>
> I think it was already discussed that we shouldn't do the
> "capability:" and "cap:" prefixes in reviews of earlier parts, so
> the details of this part would be updated?

sure

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>
>> @@ -154,10 +203,14 @@ If HEAD is a valid ref, HEAD MUST appear as the first advertised
>>  ref.  If HEAD is not a valid ref, HEAD MUST NOT appear in the
>>  advertisement list at all, but other refs may still appear.
>>
>> -The stream MUST include capability declarations behind a NUL on the
>> -first ref. The peeled value of a ref (that is "ref^{}") MUST be
>> -immediately after the ref itself, if presented. A conforming server
>> -MUST peel the ref if it's an annotated tag.
>> +In version 1 the stream MUST include capability declarations behind
>> +a NUL on the first ref. The peeled value of a ref (that is "ref^{}")
>> +MUST be immediately after the ref itself, if presented. A conforming
>> +server MUST peel the ref if it's an annotated tag.
>> +
>> +In version 2 the capabilities are already negotiated, so the first ref
>> +MUST NOT be followed by any capability advertisement, but it should be
>> +treated as any other refs advertising line.
>
> Sensible.
>
>> @@ -178,13 +231,28 @@ MUST peel the ref if it's an annotated tag.
>>    shallow          =  PKT-LINE("shallow" SP obj-id)
>>
>>    capability-list  =  capability *(SP capability)
>> -  capability       =  1*(LC_ALPHA / DIGIT / "-" / "_")
>> +  capability       =  1*(LC_ALPHA / DIGIT / "-" / "_" / "=")
>
> Ditto.
>
> Thanks.