Re: More on git over HTTP POST

From: Shawn O. Pearce <spearce@spearce.org>
Date: Aug 3, 2008, 03:31 UTC
Message-ID: <20080803033155.GC27465@spearce.org>
In-Reply-To: <7v63qiydzg.fsf@gitster.siamese.dyndns.org>

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

Show 18 quoted lines

> "Shawn O. Pearce" <spearce@spearce.org> writes:
> 
> > Show Refs
> > ---------
> >
> > Obtains the available refs from the remote repository.  The response
> > is a sequence of git "packet lines", one per ref, and a final flush
> > packet line to indicate the end of stream.
> 
> As the initial protocol exchange request, I suspect that you would regret
> if you do not leave room for some "capability advertisement" in this
> exchange.
> 
> With the git native protocol, we luckily found space to do so after the
> ref payload (because pkt-line is "length + payload" format but the code
> that reads payload happened to ignore anything after NUL).  You would want
> to define how these are given by the server to the client over HTTP
> channel.  For example, putting them on extra HTTP headers is probably Ok.

Yea, I thought that the HTTP headers would be more than enough space to add capability advertisements. Most client libraries will happily parse and store these for the application, and won't make a fuss if the application doesn't read them.

Hence there's more than enough room in the protocol to extend it in the future with additional capabilities.

We do have to be careful though. Any cachable resource must only rely upon the URI and the standard headers which compute into the cache key for a request. There aren't many, though I think the Content-Type header may be among them.

-- 
Shawn.