Automatic Julia upgrade may be surprising

[amilsted]

It's surprising to me that juliapkg will automatically pick the latest compatible Julia version from juliaup's list, even if it isn't installed, while a previous compatible version is available.

I'd prefer to default to using an installed version if it meets the Julia compat constraints. Partly this is because I want to have a way to keep a "recommended" version of Julia even if a newer version is available (see also #29).

Also, Julia Pkg now has the PRESERVE_TIERED_INSTALLED resolver mode that prefers to use compatible, already-installed versions of packages even if the registry has newer releases. It would be nice if juliapkg had a corresponding mode for Julia installation.

Could maybe make this behavior configurable?

[MilesCranmer]

+1

Yeah I think #29 would also help because we could fix a single recommended version. That way a new Julia release wouldn't instantly brick packages upon simply importing a Python package.