Re: [PATCH 5/8] Documentation: add Packfile URIs design doc

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 10, 2020, 17:16 UTC
Message-ID: <xmqqeeqmg7ty.fsf@gitster.c.googlers.com>
In-Reply-To: <20200610011406.178334-1-jonathantanmy@google.com>

Jonathan Tan <jonathantanmy@google.com> writes:

Show 13 quoted lines

>> > @@ -349,6 +362,9 @@ header. Most sections are sent only when the packfile is sent.
>> >  		  *PKT-LINE(wanted-ref LF)
>> >      wanted-ref = obj-id SP refname
>> >  
>> > +    packfile-uris = PKT-LINE("packfile-uris" LF) *packfile-uri
>> > +    packfile-uri = PKT-LINE(40*(HEXDIGIT) SP *%x20-ff LF)
>> 
>> 40* 
>
> I'm almost ready to send out an updated version, but have one question:
> what do you mean by this? If you mean that I should use "obj-id"
> instead, I didn't want to because it's not the hash of an object, but
> the hash of a packfile.

It clearly is not an object name, but it is a run of hexdigits whose length is the same as (hexadecimal representation of) the object name.

How is "obj-id" we see above in the precontext of that hunk defined? Does it use 40*(HEXDIGIT), too? Do we plan to support non SHA-1 hashes in this design in the future, and if so how?

"We are only focused on SHA-1 hashes for now" is a perfectly acceptable answer, and then 40* here makes 100% sense, but then we'd need to say "for now this design only assumes SHA-1 hash" upfront, I would think, to remind ourselves that we need to consider this part of the system when we upgrade to SHA-256.

Thanks.