Allow specifying cache outputs outside of package folder

[jaredpalmer]

This allows people to specify outputs outside of the package folder from which the command originated, which is especially useful for code-generation tools and polyglot repos. To enable this, we store artifacts in the cache relative to the root of the monorepo (see screenshot) below for before (top) and after (bottom).

Since we are changing how cache is structured, I updated the global cache key in turbo in order to prevent prior old artifacts from ever ever being cache hits with after this change

The only downside to this change, which might not be a downside at all, I guess, is possibility that artifacts are now tied to the directory structure of outputs relative to the root of the monorepo.

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[jaredpalmer]

@gsoltis is this PR and change going to work us into a weird hole in the future? im thinking that we lose flexibility by storing cache items with their directory structure, but maybe not

[gsoltis]

I guess moving a package will cause a cache miss. That seems fine.

I think we'll always know the path to the package, there's no notion of running turbo in a subtree of the repo without knowing anything about the root of the repo.

We should probably validate that the outputs are inside the monorepo if they are no longer going to be inside the corresponding tasks's package. I don't think we would want a future cache hit to make changes outside of the monorepo.

[jaredpalmer]

True but do we really care about outside of monorepo use case enough to warn against it?

[gsoltis]

I suppose "just don't do that" is ok.

[weyert]

Would this mean when I have a package package1 which part of its build or deploy uploads files to a CDN like Google Cloud Storage which final url would depended on my package2 I could save the url to a file and the package2-package directory and have the cache recover the file when a cache hit occurs?

[jaredpalmer]

@weyert it means you can do this: outputs: ['../../../some/where/in/my/monorepo/**/*'] in your pipeline

[TxHawks]

Could this change also be used in the future to enable adding files outside the package dir to a specific task's dependencies (see #706)?

I realize this isn't it, but does this change make it easier?