Re: [PATCH v2 4/8] fetch-pack: use ref adv. to prune "have" sent

> In negotiation using protocol v2, fetch-pack sometimes does not make
> full use of the information obtained in the ref advertisement:
> specifically, that if the server advertises a commit that the client
> also has, the client never needs to inform the server that it has the
> commit's parents, since it can just tell the server that it has the
> advertised commit and it knows that the server can and will infer the
> rest.
> 
> This is because, in do_fetch_pack_v2(), rev_list_insert_ref_oid() is
> invoked before everything_local(). This means that if we have a commit
> that is both our ref and their ref, it would be enqueued by
> rev_list_insert_ref_oid() as SEEN, and since it is thus already SEEN,
> everything_local() would not enqueue it.

> 
> If everything_local() were invoked first, as it is in do_fetch_pack()
> for protocol v0, then everything_local() would enqueue it with
> COMMON_REF | SEEN. The addition of COMMON_REF ensures that its parents
> are not sent as "have" lines.
> 
> Change the order in do_fetch_pack_v2() to be consistent with
> do_fetch_pack(), and to avoid sending unnecessary "have" lines.
> 
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
> ---