Re: [PATCH] protocol upload-pack-v2

The current protocol has the following problems that limit
us:

 - It is not easy to make it resumable, because we
recompute every time.  This is especially problematic for
the initial fetch aka "clone" as we will be talking about
a large transfer. Redirection to a bundle hosted on CDN
might be something we could do transparently.

 - The protocol extension has a fairly low length limit.

 - Because the protocol exchange starts by the server side
advertising all its refs, even when the fetcher is
interested in a single ref, the initial overhead is
nontrivial, especially when you are doing a small
incremental update.  The worst case is an auto-builder
that polls every five minutes, even when there is no new
commits to be fetched.

A lot of focus about the problems with ref advertisement is 
about the obvious problem mentioned above (a bad problem 
indeed).  I would like to add that there is another related 
problem that all potential solutions to the above problem do 
not neccessarily improve.   When polling regularly there is 
also no current efficient way to check on the current state of 
all refs.  It would be nice to also be able to get an 
incremental update on large refs spaces.

Thanks,

-Martin

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