Use wit-dep tool to automatically manage dependency vendoring

[lukewagner]

This PR uses @rvolosatovs's depit tool to automate the currently-manual steps of copying the Wit documents from other WASI proposal repos. (Thanks Roman!) Over time we expect this tooling to evolve further, but this seems like a pretty useful and super-easy-to-adopt short-term improvement.

@Mossaka I think this also goes a long way to addressing the concerns about manual duplication in #20, so I think it resolves that issue too?

(The world.wit files are added by actually running depit before committing; everything else was in sync already.)

cc @pchickey @sunfishcode @peterhuene

[rvolosatovs]

LGTM, just note that since you depend on main branches of these dependencies, you'd need to both delete the wit/deps.lock and clear the cache to pull in any updates in 0.2.1
depit assumes URL contents to be immutable.
Cache is located at appropriate https://docs.rs/directories/5.0.0/directories/struct.ProjectDirs.html#method.cache_dir with depit as the project name, and it's also printed with RUST_LOG=debug
Perhaps something like bytecodealliance/wit-deps#15 could be useful to address this use case better

[lukewagner]

Ah, good point. I had wondered whether it was better to use main or commit-hashes and chose main out of laziness, but maybe I should do commit hashes?

[rvolosatovs]

Ah, good point. I had wondered whether it was better to use main or commit-hashes and chose main out of laziness, but maybe I should do commit hashes?

Laziness is a virtue, I really love this approach, it requires checking-in wit/deps (which is a minuscule price to pay, since that directory only contains WIT definitions), but allows for really simple update procedure and plays well with other tooling.
I've added depit update in bytecodealliance/wit-deps#16, which is available in version 0.2.2 https://github.com/rvolosatovs/depit/releases/tag/v0.2.2

[lukewagner]

Awesome, thanks! I just updated the README.md to refer to depit update.

[Mossaka]

lgtm!