cargo-add: add feature to automatically detect missing dependencies

[brotzeit]

The idea is to parse crates from use statements(in the current buffer) and look them up in Cargo.toml. Then the user could get a minibuffer prompt containing the missing dependencies similar to Add missing dependencies: cargo add crate1 crate2 crate3.

#145

[samhedin]

Would it be easier to rely on the unresolved import error rather than parsing manually?
This would require the user to have a language server, of course.

[brotzeit]

Sounds reasonable. Most people use lsp anyway.

[samhedin]

Closing this as #161 was merged.

[brotzeit]

Unfortunately we can't merge this until it also supports eglot or it will only be loaded when lsp-mode is present.

[samhedin]

You're right, I was too quick on the trigger. I'll take a look at eglot support!

[brotzeit]

Should be working now.