Re: [PATCH 2/2] upload-pack: don't ACK non-commits repeatedly in protocol v2

> Patrick Steinhardt <ps@pks.im> writes:
> 
> > ... when the
> > server ACKs an object there is no reason for the client to go deeper, so
> > they stop advertising any of its parents.
> 
> Very true.  I did point out the difference in behaviour, but I
> couldn't actually figure out what goodness we are deriving in this
> code by marking grandparents (and possibly their ancestors) as
> something they have.  Your change in behaviour could be seen as
> stopping us from making unnecessary operations ;-)
> 
> If the other side is mischievous, they are not limited to feed us a
> commit and then its parent in the naturally expected order.  They
> could feed us A and then skip B and give us C that is a child of B.
> Pre-painting B when we got A from them, in order to prepare for
> seeing B (which we can return without doing anything) in the next
> round, would not help us all that much, if they give us C after
> giving us A, as we haven't even heard of C yet at that point.

> But in the normal case against sane clients that do not skip the
> probes, marking immediate parents (like B) when processing A might
> be helping?  I dunno.  I also somehow thought that even normal case
> we have an option to skip the probes in order to converge faster,
> but I am misremembering.
> 
> cf. https://lore.kernel.org/git/?q=upload-pack%20fibonacci