fix(nushell): Use def --env instead of def-env

[hyperupcall]

Summary

Nushell recently deprecated use of def-env. Migration is clear. This issue implements the deprecation and this issue implements def --env. It states:

Because def-env is used everywhere, including virtualenv, I propose the following steps:

• 0.86: Add this PR, keep def-env and extern-wrapped unchanged.
• 0.87: Add deprecation warning to def-env and extern-wrapped but keep them working.
• 0.88 (or later): Remove def-env and extern-wrapped.

So, the minimum version needs to be bumped to 0.86. Unfortunately, this means older versions will no longer be support, but it is difficult as nushell has many backwards incompatible changes being made

Current version of nushell is 0.87.0, which was released last week. To ensure this fix gets merged before the release of 0.88.0, it should be merged before ~December 13

Closes #1680
Closes #1700

[hyperupcall]

@jthegedus @Stratus3D this is an urgent bugfix. When the latest version of nushell is released in a few weeks, asdf will break without this patch.

Aside: Will it be possible to review my other PRs as well?

[acidghost]

@jthegedus @Stratus3D ping.

Nushell 0.88 has been released with def-env removed, meaning that asdf cannot be used from nushell.
Can you please merge this PR and release a new version of asdf?

[hyiltiz]

This is a minimal change that has no impact to any part of asdf core mechanics and only updates asdf autocomplete interface for nushell. As of the last few updates, the script shipped with asdf simply throws a syntax error in nushell, as def-env is now an undefined symbol. Please merge asap.

[jthegedus]

@hyperupcall GitHub is not letting me modify this PR because of the source fork permissions so I cannot resolve the conflict (Fish version update), can you update this when you have the time? Thanks

[jthegedus]

Thanks