config 1.0 backend

[Gankra]

half of #841 (see that for high level design docs)

---

• move current config to v0 module
• create v1 config
  • definitions
  • inheritance (workspace -> package)
  • inheritance (installer -> installer.shell)
  • simple defaults
  • make_relative_to
  • complex defaults ("enable build cache if config x or y are enabled")
  • complex validation ("you flipped on x and y this makes no sense")
  • toml deserialization (impl'd but untested)
  • [ ] toml serialization (the code init does with toml-edit)
  • 1 million doc comments
• use v1 config internally
  • create v0_to_v1 translation layer
  • apply translation layer to current v0 config to also construct v1 in parallel
  • change internal code that uses workspace config to use v1
  • change internal code that uses package config to use v1
• [ ] expose v1 config to end-users (probably not in this PR)
  • [ ] read either v0 or v1 in, branching on which it is
  • [ ] create v1 with init
  • [ ] auto-translate v0 to v1 in init

[Gankra]

Right now the biggest issue I'm running into is how "random" it is that something is a global setting or not, and the fact that a global setting vs a package-local setting requires a bunch of duplicated definitions/logic. I tried to do a cheeky split of "only ci config is global" but a lot of not-actually-ci-config is defacto-ci-config like github releases or build dependencies.

I'm going to try to do the package-local settings first to see if they're easier to migrate.

[Gankra]

complex defaults ("enable build cache if config x or y are enabled")

This design is based entirely on the config overhaul i did in oranda last year, and it also had a last-step freeform system for Complex Defaults:

https://github.com/axodotdev/oranda/blob/0044504916cfbeaf5a830d8703828a81375b3362/src/config/mod.rs#L260-L271

My main annoyance here is that "defaults last" means some things have to be Options in the final config (or we add a 4th fucking copy of every struct ;-;). In practice a few extra options you have to unwrap is..... Probably Fine.

[Gankra]

This doc-comment in oranda is quite informative about the basic idea of the design: https://github.com/axodotdev/oranda/blob/0044504916cfbeaf5a830d8703828a81375b3362/src/config/mod.rs#L1

What this design adds is an extra "Inheritable" thing between Config and Layer to represent the delayed application of inherited values like installers.install_path onto installers.shell.install_path.

This results in there being 4 possible values any given setting can come from, which need to apply in this exact preference order

• workspace.publish.prerelease
• workspace.publish.cargo.prerelease
• package.publish.prerelease
• package.publish.cargo.prerelease

you need the accursed middle struct to handle cases like

• workspace.publish.prelease = true
• package.publish.cargo = true

(cargo is enabled within a package, but doesn't specify its prerelease preferences, so the prerelease setting needs to be inherited from the workspace all-publishes setting. The workspace.publish.prerelease setting therefore can't be eagerly merged into workspace.publish.cargo.prerelease, because workspace.publish.cargo = None.)