'none' tag for project with 'rust-toolchain' file

[DCjanus]

There are some project put rust-toolchain file in root directory, for example: nightly-2019-05-22.

With those project, no matter which tag I choose, I have to info: syncing channel updates for 'nightly-2019-05-22-x86_64-unknown-linux-gnu' when I build the docker image, even I chosed clux/muslrust:nightly-2019-05-22(because this image installed nightly channel toolchain rather than nightly-2019-05-22).

If I have to download toolchain, maybe image without pre-installed toolchain is better?

The way to install rustup without pre-installed toolchain is:

curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain none

[clux]

There has to be a default toolchain installed for builds to work in most places though, and the image is purposefully built with the entire toolchain. Downloading another update inside this image is counterproductive (you'd just download another image instead).

Maybe if we installed with the explicit nightly we expect to be available?

e.g. something like --default-toolchain nightly-$(date +"%Y-%m-%d")

[DCjanus]

That sounds good to me