upgrading from non-profiles rustup to profiles rustup should auto-add profile= in settings.toml just like first time install does

[ghost]

Describe the problem you are trying to solve

if rustup update will pull a rustup which now has profiles support, the profile= key/value in ~/.rustup/settings.toml will not be added(presumably, I haven't actually tested xD).

Describe the solution you'd like

I dno.

Notes

A side effect of not having profile= set in settings.toml is that you can't install any specific nightly version, as seen here

Workaround is running rustup set profile or rustup set profile minimal, the former sets profile = default in ~/.rustup/settings.toml and the latter sets profile = minimal which seems to match the non-profiles version of rustup that just got upgraded.

Also note that any/all comments in settings.toml are removed by running rustup set profile, or more specifically this code