Re: [PATCH] Update packfile transfer protocol documentation

From: Shawn O. Pearce <spearce@spearce.org>
Date: Nov 2, 2009, 23:57 UTC
Message-ID: <20091102235707.GV10505@spearce.org>
In-Reply-To: <7vzl74trmc.fsf@alter.siamese.dyndns.org>

Junio C Hamano <gitster@pobox.com> wrote:

Show 12 quoted lines

> Scott Chacon <schacon@gmail.com> writes:
> > +
> > +A pack-file MUST be sent if either create or update command is used.
> 
> Easier to read if MUST is followed by "_even_ if", like so:
> 
>     ... MUST be sent when a create or update command is used, even if the
>     server already has all the necessary objects.
> 
> Shouldn't we say "the client MUST NOT make reference update request if
> everything is up to date" which would imply that in practice there is no
> reason to send an empty pack data?

Create a new branch to point at an existing object. Branch creation causes a pack to be expected, but if you are creating a new branch that points at an existing object there is nothing to pack. E.g.:

  git remote add -f A user@host:proj.git
  git push A A/master:refs/heads/new-branch

causes a 0 object pack file to be sent, assuming the remote project's
master branch has not changed in between the two commands.

> > +  pack-file         = "PACK" 24*(OCTET)
> 
> Curious---where does this 24 come from?

Hmmph.  Its wrong actually.  I was trying to write the minimum
number of bytes that make up a pack file, which is actually 28.
(12 in the header minus 4 as "PACK" was already spelled out, plus
20 in the footer for the SHA-1).

-- 
Shawn.