[RFC] Allow to configure all options via env vars

[stszap]

Describe the feature you'd like to request

It would be really nice to be able to specify all options via environmental variables. For example, I would like to be able to configure --cache-dir or --concurrency in CI (which I maintain) without adding more configuration to turbo.json or package.json (which are maintained by developers). This will also allow developers to have some unique configurations but still share package.json with the same commands. Also, setting env vars is much easier than constructing cli options and can greatly simplify scripting.

Describe the solution you'd like

I think thank npm approach is very convenient and because options in turbo are "flat" they can simply be translated to env vars with TURBO_ prefix. For example:
--filter -> TURBO_FILTER
--no-cache-> TURBO_NO_CACHE
--continue -> TURBO_CONTINUE
This also aligns with existing variables (TURBO_FORCE, TURBO_TOKEN etc) which do exactly what this request is about.

Describe alternatives you've considered

We can add multiple commands to package.json like this:

  "scripts": {
    "build-local": "turbo run build --concurrency=2 --continue",
    "build-ci": "turbo run build --concurrency=100% --cache-dir=/mnt/cache",
    ...
  },

But this causes duplicated options if we want to share them, clutters package.json and makes scripting more difficult if we want to compute some options on the fly and can't hardcode them.

[jlarmstrongiv]

Yep, I’ve wished I had this for the --concurrency option for a while now.

[weyert]

Yeah, that would be nice :)
Sadly, the chosen cli library for Go doesn't appear to support this out of the box. I think some sort of adapter/wrapper is necessary to easily cover this

[jlarmstrongiv]

Related #1324

[RobinVdBroeck]

Bump, we would like to be able to do this for concurrency.