Comment by nightpool

Seems like they actually sped bun up ~1x:

    When evaluating the complete bun install improvements, it came out speed-wise to about the same as the existing git usage (due to networking being the big bottleneck time-wise despite more cases being slightly faster with ziggit over multiple benchmarks). Except, it's done in 100% zig and those internal improvements pile up as projects consist of more git dependencies. All in all, it seems like a sensible upstream contribution.

So you have to maintain a completely separate git implementation and keep that up to date with upstream git, all for the benefit of being indistinguishable on benchmarks. Oh well!