Re: [PATCH v3 0/8] Hiding refs

From: Jeff King <peff@peff.net>
Date: Mar 11, 2014, 20:36 UTC
Message-ID: <20140311203650.GA31173@sigill.intra.peff.net>
In-Reply-To: <xmqq4n34pjnw.fsf@gitster.dls.corp.google.com>

On Tue, Mar 11, 2014 at 01:25:23PM -0700, Junio C Hamano wrote:

Show 21 quoted lines

> > Yeah, good idea. I might be misremembering some complications, but we
> > can probably do it with:
> >
> >   1. Teach the client to send an "advertise-symrefs" flag before the ref
> >      advertisement.
> >
> >   2. Teach the server to include symrefs in the ref advertisement; we
> >      can invent a new syntax because we know the client has asked for
> >      it.
> 
> I was thinking more about the underlying protocol, not advertisement
> in particular, and I think we came to the same conclusion.
> 
> The capability advertisement deserves to have its own separate
> packet message type, when both sides say that they understand it, so
> that we do not have to be limited by the pkt-line length limit.  We
> could do one message per capability, and at the same time can lift
> the traditional "capability hidden after the NUL is purged every
> time, so we need to repeat them if we want to later change it,
> because that is how older clients and servers use that information"
> insanity, for example.

So this may be entering the "more radical changes" realm I mentioned earlier.

If the client is limited to setting a few flags, then something like http can get away with:

  GET foo.git/info/refs?service=git-upload-pack&advertise-symrefs&refspec=refs/heads/*

And it does not need to worry about upload-pack2 at all. Either the server recognizes and acts on them, or it ignores them.

But given that we do not have such a magic out-of-band method for passing values over ssh and git, maybe it is not worth worrying about. Http can move to upload-pack2 along with the rest.

One thing that _is_ worth considering for http is how the protocol starts. We do not want to introduce an extra http round-trip to the protocol if we can help it. If the initial GET becomes a POST, then it could pass along the pkt-line of client capabilities with the initial request, and the server would respond with the ref advertisement as usual.

-Peff