Re: [PATCH v3 0/8] Hiding refs

[Junio C Hamano <gitster@pobox.com>]

Jonathan Nieder <jrnieder@gmail.com> writes:

>> * I didn't see a response to Peff's convincing arguments that this
>> should be a client-side feature rather than a server-side feature [1].
>
> The client can't control the size of the ref advertisement.  That is
> the main motivation if I understood correctly.

The answer to this question is more nuanced.

With the current protocol, it is upload-pack who speaks first, so
there is no way for the requestor to say "I am from an updated Git
suite and understand how to tell you to give me limited set of
refs", before upload-pack blasts 4MB of ref advertisement to it.

If the side that fetches is potentially interested in finding out
any and all refs, then an alternative solution would be to break
the current protocol, open a separate port and have upload-pack-2
listen to it, sit silently to let the requestor speak first when it
gets connection to that port.

But if the primary thing you are interested in is to hide the
references that:

 (1) the server side needs to keep track of for its own use; but
 (2) the requestors do not have to learn about from upload-pack,

we can do so without breaking older requestors.  That is what the
early part of this series is about.  We can view the last patch to
add the allow-tip-sha1-in-want as an icing on the cake.

It has the side effect of reducing the transfer overhead, because by
hiding the internal refs, the server side will stop blasting 4MB of
ref advertisements the requestors are not interested in, and that
would be the primary observable outcome from the end-user's point of
view (i.e. your "git pull --ff-only" will become a lot faster).