Support creating sub-shell with separate environment/cwd

[JohnnyCrazy]

Hi,

Is something like within supported yet, see zx docs? I think it spawns a sub-shell under the hood, which allows to have a separate environment and also change the cwd isolated.

My use-case is to run build processes in different directories parallel, sth like this:

// in project1
await $`build`;
await cd("../cdk");
await Promise.all([
  within(async () => {
    await $`deploy-1`;
    await $`deploy-2`;
    await $`deploy-3`;
  }),
  within(async () => {
    await cd("../project2");
    await $`build`;
    await cd("../cdk");
    await $`deploy-4`;
  }),

I tried using $.build$({}) but it shares the cwd with the main $, doesn't it?

#!/usr/bin/env tsx
import $ from "dax-sh"; // "dax-sh" in Node
$.setPrintCommand(true);

const other$ = $.build$({});
$.cd("/tmp");

await other$`echo $PWD`;
await $`echo $PWD`;

❯ test_dax
> echo $PWD
/private/tmp
> echo $PWD
/private/tmp