Re: [PATCH v2] fetch-pack: add tracing for negotiation rounds

> Currently, negotiation for V0/V1/V2 fetch have trace2 regions covering
> the entire negotiation process. However, we'd like additional data, such
> as timing for each round of negotiation or the number of "haves" in each
> round. Additionally, "independent negotiation" (AKA push negotiation)
> has no tracing at all. Having this data would allow us to compare the
> performance of the various negotation implementations, and to debug
> unexpectedly slow fetch & push sessions.
> 
> Add per-round trace2 regions for all negotiation implementations (V0+V1,
> V2, and independent negotiation), as well as an overall region for
> independent negotiation. Add trace2 data logging for the number of haves
> and "in vain" objects for each round, and for the total number of rounds
> once negotiation completes.  Finally, add a few checks into various
> tests to verify that the number of rounds is logged as expected.
> 
> Signed-off-by: Josh Steadmon <steadmon@google.com>