In a directory with an override, display override after succesful default change

[carols10cents]

The problem I am trying to solve

I have some directories where I've set overrides and some directories where I haven't set overrides, and I don't remember which directories have overrides or not.

I'll be working on a project and want to change the Rust version I'm currently using, so I'll run:

$ rustup default beta

Which outputs:

info: using existing install for 'beta-x86_64-apple-darwin'
info: default toolchain set to 'beta-x86_64-apple-darwin'

  beta-x86_64-apple-darwin unchanged - rustc 1.33.0-beta.4 (635817b9d 2019-01-24)

So I say, "cool, I'm using beta now!" and go about cargo building, etc.

In a directory without an override, I am indeed using beta.

In a directory with an override, I get the same output, but I am not using beta (necessarily), I'm using the override. So I cargo build thinking I'm on beta, but I'm not.

The solution I'd like

If I'm in a directory without an override, I'd like the current behavior of rustup default to stay the same.

If I'm in a directory with an override, I'd like the output of rustup default to remind me that I have an override and that I'm not using the default that I just changed. Something like:

$ rustup default beta
info: using existing install for 'beta-x86_64-apple-darwin'
info: default toolchain set to 'beta-x86_64-apple-darwin'

  beta-x86_64-apple-darwin unchanged - rustc 1.33.0-beta.4 (635817b9d 2019-01-24)

(currently using 1.24.1-x86_64-apple-darwin, directory override for '/Users/carolnichols/rust/carol-test')

If this is a personal problem of mine, I can script my way around it, but I wanted to file this and see what others thought and then potentially submit a PR if other folks have this problem too.

[dwijnand]

Note we're about to make rustup default (without any arguments) more informative: #1633, though I don't know how that behaves with overrides present (cc @lazorgator).

Advising the user that even after changing the default a directory override is present sounds like a good idea to me. I think it should do it for all methods that have precedence on the default, as described in https://github.com/rust-lang/rustup.rs/blob/1.16.0/README.md#override-precedence. So if there is a rust-toolchain file or a RUSTUP_TOOLCHAIN env var.

[das-sein]

@dwijnand At present, the rustup default only returns the global default toolchain. Maybe it should detect if there is an override and output that along with the default? Something like:

canis@latrans:~/rustup.rs$ rustup default
Default toolchain: stable-x86_64-unknown-linux-gnu
Current override: nightly-x86_64-unknown-linux-gnu

[das-sein]

@carols10cents Opened a PR. I liked your idea better, so the change will result in some lines of logging being output to notify you of an override being set, and why it is set.

[carols10cents]

Awesome, thank you @lazorgator !!!!