feat: add nix caching

[shyim]

• Added caching for devenv up and devenv shell
• Replaced nix develop with just invoking the user shell, therefore we use still the normal shell
• Fixed some warnings while cargo build
• Find a solution for enterShell hooks when not calling bash anymore
• Add a --no-cache flag to skip caching
• Improve code style 🙈

Fixes #1079

No cache:

❯ time devenv shell -- whoami
shyim

________________________________________________________
Executed in    6.61 secs      fish           external
   usr time   27.40 millis   47.00 micros   27.35 millis
   sys time   20.56 millis  845.00 micros   19.72 millis

Cached environment execution:

❯ time devenv shell -- whoami
shyim

________________________________________________________
Executed in   37.70 millis    fish           external
   usr time   19.73 millis   30.00 micros   19.70 millis
   sys time   13.26 millis  517.00 micros   12.75 millis

Native without devenv

❯ time whoami
shyim

________________________________________________________
Executed in    5.89 millis    fish           external
   usr time    1.76 millis    0.03 millis    1.73 millis
   sys time    2.52 millis    1.02 millis    1.50 millis

[domenkozar]

Why don't we use print_dev_env function when we know it's cached?

This also needs to respect imports in devenv.yaml when calculating the hash.

[shyim]

print_dev_env is called by direnv and direnv does his own caching 🤔
I am not sure if we want to ditch the caching of direnv completely, as it right now works fine 🤔. and we would at least have ~30ms latency switching between projects as devenv needs to be called

[domenkozar]

print_dev_env is called by direnv and direnv does his own caching 🤔 I am not sure if we want to ditch the caching of direnv completely, as it right now works fine 🤔. and we would at least have ~30ms latency switching between projects as devenv needs to be called

Could you explain the goal of this PR? Then it makes it easier to discuss possible implementations :)

[shyim]

Make devenv shell and devenv up faster on existing projects without any changes. When merging the direnv caching is possible, it would be nice to have one place of caching.

[domenkozar]

So kind of like direnv caching without direnv?

[shyim]

Yes excactly

[domenkozar]

I'll tackle this shortly, it's important to get back to blazing fast :)

[shyim]

further random idea: Could we get from one nix eval back all environment variables + the process startup script.

Instead of right now doing three nix commands, we could do only one 🤔

[domenkozar]

That's actually what I'm exploring, we'd need to reimplement print-dev-env in Rust and then we got it all.

Will post results as soon as I get something working!