Re: How to resume broke clone ?

From: Jeff King <peff@peff.net>
Date: Dec 5, 2013, 19:08 UTC
Message-ID: <20131205190824.GA19039@sigill.intra.peff.net>
In-Reply-To: <xmqqeh5ri3d3.fsf@gitster.dls.corp.google.com>

On Thu, Dec 05, 2013 at 10:01:28AM -0800, Junio C Hamano wrote:

Show 10 quoted lines

> > You could have a "git-advertise-upstream" that generates a mirror blob
> > from your remotes config and pushes it to your publishing point. That
> > may be overkill, but I don't think it's possible with a
> > .git/config-based solution.
> 
> I do not think I follow.  The upload-pack service could be taught to
> pay attention to the uploadpack.advertiseUpstream config at runtime,
> advertise 'mirror' capability, and then respond with the list of
> remote.*.url it uses when asked (if we go with the pkt-line based
> approach).

I was assuming a triangular workflow, where your publishing point (that other people will fetch from) does not know anything about the upstream. Like:

  $ git clone git://git.kernel.org/pub/scm/git/git.git
  $ hack hack hack; commit commit commit
  $ git remote add me myserver:/var/git/git.git
  $ git push me
  $ git advertise-upstream origin me

If your publishing point is already fetching from another upstream, then yeah, I'd agree that dynamically generating it from the config is fine.

Show 7 quoted lines

> Alternatively, it could also be taught to pay attention
> to the same config at runtime, create an blob to advertise the list
> of remote.*.url it uses and store it in refs/mirror (or do this
> purely in-core without actually writing to the refs/ namespace), and
> emit an entry for refs/mirror using that blob object name in the
> ls-remote part of the response (if we go with the magic blob based
> approach).

Yes. The pkt-line versus refs distinction is purely a protocol issue. You can do anything you want on the backend with either of them, including faking the ref (you can also accept fake pushes to refs/mirror, too, if you really want people to be able to upload that way).

But it is worth considering what implementation difficulties we would run across in either case. Producing a fake refs/mirror blob that responds like a normal ref is more work than just dumping the lines. If we're always just going to generate it dynamically anyway, then we can save ourselves some effort.

-Peff