threads / discuss / 27102

capturing the packfile from git-upload-pack

Subject: capturing the packfile from git-upload-pack

## tl;dr

6 messages between Apr 15, 2011 and Apr 16, 2011.

replies: 5people: 4as markdown or json

madmarcos· Apr 15, 2011, 03:22 UTC · lore

Hi folks, is there a git command that can capture in a separate file the packfile that is generated and transmitted from a "want"ed branch during the git-upload-pack command? I need a good sample to study. thanks!

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Shawn Pearce· Apr 15, 2011, 15:46 UTC · re: madmarcos · lore

Re: capturing the packfile from git-upload-pack

On Thu, Apr 14, 2011 at 23:22, madmarcos <fru574@my.utsa.edu> wrote:

> is there a git command that can capture in a separate file the packfile that
> is generated and transmitted from a "want"ed branch during the
> git-upload-pack command? I need a good sample to study.

No.

But you can create an input file yourself, the pkt-line format is pretty simple. Pipe the input to git-upload-pack, and it will spit back the response. :-)

-- 
Shawn.

Junio C Hamano· Apr 15, 2011, 17:46 UTC · re: Shawn Pearce · lore

Re: capturing the packfile from git-upload-pack

Shawn Pearce <spearce@spearce.org> writes:

Show 10 quoted lines

> On Thu, Apr 14, 2011 at 23:22, madmarcos <fru574@my.utsa.edu> wrote:
>> is there a git command that can capture in a separate file the packfile that
>> is generated and transmitted from a "want"ed branch during the
>> git-upload-pack command? I need a good sample to study.
>
> No.
>
> But you can create an input file yourself, the pkt-line format is
> pretty simple. Pipe the input to git-upload-pack, and it will spit
> back the response. :-)

If you are running 1.7.5-rc0 or newer, GIT_TRACE_PACKET may also be of help.

Jeff King· Apr 15, 2011, 19:09 UTC · re: Junio C Hamano · lore

Re: capturing the packfile from git-upload-pack

On Fri, Apr 15, 2011 at 10:46:28AM -0700, Junio C Hamano wrote:

Show 15 quoted lines

> Shawn Pearce <spearce@spearce.org> writes:
> 
> > On Thu, Apr 14, 2011 at 23:22, madmarcos <fru574@my.utsa.edu> wrote:
> >> is there a git command that can capture in a separate file the packfile that
> >> is generated and transmitted from a "want"ed branch during the
> >> git-upload-pack command? I need a good sample to study.
> >
> > No.
> >
> > But you can create an input file yourself, the pkt-line format is
> > pretty simple. Pipe the input to git-upload-pack, and it will spit
> > back the response. :-)
> 
> If you are running 1.7.5-rc0 or newer, GIT_TRACE_PACKET may also be of
> help.

Sadly, no. I punted on outputting the actual pack since it is big and binary, and I was only interested in the ref negotiation. My eventual plan was that you could do:

  GIT_TRACE_PACKET=2 GIT_TRACE_PACKET_PACK=/tmp/foo.pack \
    git clone ...

and get the ref negotiation on stderr, and the pack dumped in a file. However, there is one stumbling block: the packet tracing happens at a very low level, and doesn't know if we are doing sideband-demuxing or not. And it would need to know to that to put the proper data in the packfile.

It may just be a matter of implementing the packfile tracing at a slightly different layer (where we have already demuxed), but I haven't looked closely at it.

-Peff

Jeff King· Apr 15, 2011, 19:25 UTC · re: Jeff King · lore

Re: capturing the packfile from git-upload-pack

On Fri, Apr 15, 2011 at 03:09:08PM -0400, Jeff King wrote:

Show 24 quoted lines

> On Fri, Apr 15, 2011 at 10:46:28AM -0700, Junio C Hamano wrote:
> 
> > Shawn Pearce <spearce@spearce.org> writes:
> > 
> > > On Thu, Apr 14, 2011 at 23:22, madmarcos <fru574@my.utsa.edu> wrote:
> > >> is there a git command that can capture in a separate file the packfile that
> > >> is generated and transmitted from a "want"ed branch during the
> > >> git-upload-pack command? I need a good sample to study.
> > >
> > > No.
> > >
> > > But you can create an input file yourself, the pkt-line format is
> > > pretty simple. Pipe the input to git-upload-pack, and it will spit
> > > back the response. :-)
> > 
> > If you are running 1.7.5-rc0 or newer, GIT_TRACE_PACKET may also be of
> > help.
> 
> Sadly, no. I punted on outputting the actual pack since it is big and
> binary, and I was only interested in the ref negotiation. My eventual
> plan was that you could do:
> 
>   GIT_TRACE_PACKET=2 GIT_TRACE_PACKET_PACK=/tmp/foo.pack \
>     git clone ...

Actually, thinking on it more, this is kind of stupid. The pack that we fetch will end up in .git/objects/pack, so it's not that interesting to dump (though I suppose in a fetch setting, you might want to actually peek at the thin pack before it gets resolved).

More interesting is for the sender to dump the pack they send, which would mean instrumenting pack-objects.

Or, as Shawn suggested, poking upload-pack yourself using a conversation you read from GIT_TRACE_PACKET. Which is probably what you meant when you suggested it in the first place. So I'll shut up now.

-Peff

madmarcos· Apr 16, 2011, 00:59 UTC · re: Shawn Pearce · lore

Re: capturing the packfile from git-upload-pack

Thanks, Shawn. Worked like a charm. Sometimes I forget the awesomeness that is Unix.

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