Re: [PATCH V1][RFC] t/perf/p3400: speed up setup using fast-import

I noticed that while the setup phase is much faster (as shown in the commit message), the actual rebase performance test regressed slightly by about 3 seconds (from ~2s to ~5s). I don't quite understand what led to this outcome.

Additionally, I haven't delved deeply into the technical details of `git fast-import`, and I'm not entirely sure if my approach is reasonable and compliant with the specifications.

I would greatly appreciate any guidance from those knowledgeable in these area!

Regards, Yuchen