spago upstream command

[f-f]

It is usual to add packages that are not in the package-set to the packages.dhall (I mean, this is basically our main feature). It would be nice to have an easy way to have them contributed to the upstream package-set, e.g. with something like spago upstream whatever-package.

What this command would do is:

• check that the package is not in the upstream package-set (if it is, prompt the user to upgrade)
• if it's not, open a pull request to spacchetti (e.g. with this) (note: we'll need to think of a way to handle auth. I guess passing a github token with a flag could be ok?)

[f-f]

I guess this is kind of a deal-breaker though (from Github docs):

[JordanMartinez]

This is also listed as a preview features, so that condition might drop in the future.

[f-f]

Yeah, though the problem of authentication still stands (you have to be authenticated AND to have a fork of spacchetti in your account, which is unlikely).

Instead it would probably work better to just:

1. print out a bunch of information about how much our package set is not in sync with our current one (additions, version upgrades, different upstream), and
2. print out a URL to automatically open an issue, prepopulated with useful info for us (so we can just copypaste it into a PR for spacchetti, or have @spacchettibotti open PRs for us), like: https://github.com/spacchetti/spacchetti/issues/new?title=Spago+Upstream+Request&body=blabla

[f-f]

This together with #89 would be the "publishing flow": we could include a spago publish command that does the spago upstream of the current package. We would need to require a git url to be in the spago.dhall, and if we require it to be a GitHub repo we could search for releases and pick the most recent.

[f-f]

I'm going to close this as it looks like this is not something that we clearly want. I suspect something along the lines of this command might pop up when designing the new registry, but I think we can archive this for now.