Use Nix copy command instead of nix-closure-copy

[smulikHakipod]

This relates to #63
I tested it, and its very fast.
It only work fast on NisOS unstable though, as NixOS 23.05 contains Nix 2.13 which doesn't support that yet.
On older nixos it just works slowly.

[exarkun]

I tested it, and its very fast.

Can you provide some numbers to go with this? How does it deal with latency?

[smulikHakipod]

@exarkun sure,
here is a time terraform apply -auto-approve on some example terraform on AWS (with around 100ms latency) and sample nix config without the patch:

terraform apply -auto-approve 14.52s user 4.95s system 3% cpu 8:26.58 total

and here is with the patch (on completely new machine):

terraform apply -auto-approve 7.47s user 1.55s system 14% cpu 1:00.89 total

More than 8x improvment.

[exarkun]

Now that this project is maintained by nix-community, maybe this PR can be merged? :) Or at least reviewed by a maintainer and whatever changes are necessary requested.

I was away from deploy_nixos for a while but, if this project is maintained, there's a good chance I'll start using it again in a new project.

[adrian-gierakowski]

@exarkun i don’t have capacity to test this right now. I’d be happy to merge it if it was opt-in. Can we add a flag in the terraform module to switch between original implementation and this one? Thanks!