Move the edition guide to a more prominent location

[Centril]

We should eventually move the guide out of the https://rust-lang-nursery.github.io/ URL and give it a more official-looking, short and sweet URL instead.

We decided that we will punt on this for Preview 2; but we should do this for Release Candidate 1.

A suggested URL for the whole edition is https://rust-lang.org/edition/ and https://rust-lang.org/edition/2018/ then goes to the 2018 page.

We can also move it to https://docs.rust-lang.org/edition/

[orium]

Note that when this is done some urls in cargo will need to be updated. At the time of this comment there are two references to rust-lang-nursery.github.io:

orium@laptop-orion cargo % rp rust-lang-nursery.github.io
src/cargo/util/diagnostic_server.rs
174:  https://rust-lang-nursery.github.io/edition-guide/editions/transitioning-your-code-to-a-new-edition.html
196:  https://rust-lang-nursery.github.io/edition-guide/editions/transitioning-your-code-to-a-new-edition.html

[steveklabnik]

This is not happening as part of the release candidate, so de-milestoning.

[tmandry]

Will this happen before release? It looks like there was some mention on Discord, but no formal decision made.

At least one rustc PR (rust-lang/rust#55185) includes a guide URL; we're not sure if it's going to change.

[dwijnand]

https://doc.rust-lang.org/stable/edition-guide/ is now a thing, but note that it's some other version of the guide that isn't https://rust-lang-nursery.github.io/edition-guide/.

Note the "Minimum Rust Version" in:

• https://doc.rust-lang.org/stable/edition-guide/rust-2018/ownership-and-lifetimes/non-lexical-lifetimes.html, vs
• https://rust-lang-nursery.github.io/edition-guide/rust-2018/ownership-and-lifetimes/non-lexical-lifetimes.html

[dwijnand]

Interestingly hasn't changed with the 1.32 release.

[sdht0]

I think the minimum versions needs an update at https://doc.rust-lang.org/stable/edition-guide/rust-2018/documentation/new-editions-of-the-book.html