[bin wrappers] fixes for only-path-without-wrappers call

[savil]

Summary

follow up to #1160

correctness:

• consolidate some code into calling wrapnix.GetWrapperBinPath
• the earlier code had a bug where I forgot to call -c <project dir>, but that is moot now (see below change)

perf:

• call DO_NOT_TRACK=1 to minimize segment perf impact
• simplify OnlyPathWithoutWrappers to directly call os.Getenv("PATH"), remove WrapperBins, and exportify it. This function is used in a very specific context, so we can know we can skip the nix.ComputeEnv calculation.
• Doing time devbox shellenv only-path-without-wrappers is now consistently ~ 18-25 milliseconds.

I have a slight preference for this over writing PATH to a file and sourcing it, since we may run into correctness issues with that file getting outdated, and it'll introduce perf regression on every shellenv call to write the file.

How was it tested?

• testscripts pass
• iex -S mix works

visual inspection:

    1 #!/nix/store/w849dr5qcbrrnxv69sy7kdnifa9jpjyf-bash-5.2-p15/bin/bash
  2
  3
  4
  5 if [[ "$__DEVBOX_SHELLENV_HASH_ac6a60d54a9d1ba6618cce8d40bfdfb50059d814edfe5f49bca3168c5c34e970" != "b1a4903de70aa4d610ecb00ffb3dd755913b4505651e6bebbf41571a406d415c" ]] &    & [[ -z "$__DEVBOX_SHELLENV_HASH_ac6a60d54a9d1ba6618cce8d40bfdfb50059d814edfe5f49bca3168c5c34e970_GUARD" ]]; then
  6 export __DEVBOX_SHELLENV_HASH_ac6a60d54a9d1ba6618cce8d40bfdfb50059d814edfe5f49bca3168c5c34e970_GUARD=true
  7 eval "$(DO_NOT_TRACK=1 devbox shellenv -c /Users/savil/code/jetpack/devbox/examples/development/elixir/elixir_hello)"
  8 fi
  9
 10 eval "$(DO_NOT_TRACK=1 devbox shellenv only-path-without-wrappers -c /Users/savil/code/jetpack/devbox/examples/development/elixir/elixir_hello)"
 11
 12 exec /nix/store/47whvyx9x48ishndcjw71xs7l0a6v6sd-elixir-1.14.4/bin/iex "$@"

[savil]

Current dependencies on/for this PR:

• main
  • PR [bin wrappers] fixes for only-path-without-wrappers call #1163 👈

This comment was auto-generated by Graphite.

[mohsenari]

What was the reason for skipping adding this to Devbox interface?

[savil]

Its a small utility function which doesn't have any dependency on the core "devbox" struct.

I was going to inline it in boxcli/shellenv.go, but needed the exportify function so added it here.

[mohsenari]

os.Getenv("PATH") works because OnlyPathWithoutWrappers is used only in the context of direnv enabled or inside devbox shell. So the PATH is guaranteed to be a devbox computed PATH.
But it won't work outside that context, if you just run the command you'll get PATH env variable (assuming you don't have devbox global).
So I worry this might be used in future in a different context with the assumption that it will compute a devbox PATH and exclude wrappers bin and introduce a bug.

[savil]

1. The devbox shellenv only-path-without-wrappers command is Hidden, and I can add more comments to clarify its usage. It'll only be used by someone developing devbox code. So, this is low risk.

2. The internal function could be renamed to ExportSystemPathWithoutWrappers. WDYT?

[mohsenari]

yeah the rename can clarify the usage then

[LucilleH]

This solution is much better than the one I suggested in the previous PR!