cli: completion: Add support for Nushell completions

[poliorcetics]

Incidentally, I also fixed outdated docs in the command help for other shells (still using --<shell> instead of the positional form)

Checklist

If applicable:

• I have updated CHANGELOG.md
• I have updated the documentation (README.md, docs/, demos/) (command documentation)
• I have updated the config schema (cli/src/config-schema.json)
• I have added tests to cover my changes

Dependencies

• Needs fix(clap_complete_nushell): correctly handle commands whose short description is more than one line clap-rs/clap#5359 to work

• Needs completion: Update docs for new style with positional argument #3074

• Closes cli: add nushell completion support #2353

• Closes FR: nushell completion support  #2323

[PhilipMetzger]

LGTM, could you please adhere to our commit style too, like cli: and lib:?

[PhilipMetzger]

And it seems someone forgot to update the snapshot of the cli-reference.

[poliorcetics]

@PhilipMetzger done to both !

[thoughtpolice]

Note that in #2353 this was also attempted, but due to a bug in clap_complete_nushell it actually generates invalid nushell code. I assume your upstream commit fixes this behavior? If so it might make sense to mark the upstream clap bug/PR as completed as well as the earlier one here.

[poliorcetics]

I assume your upstream commit fixes this behavior

Yes, and it's been released with 4.5.1, so this PR is now ready. Thanks for pointing out the existing issues and PRs :)

[PhilipMetzger]

Can you add a Closes #2323 to the commit message or the PR description? Then it should be good to land.

[poliorcetics]

Yes done

[thoughtpolice]

lgtm 👍🏻

[poliorcetics]

Rebased on top of #3062 so I can finally merge them sequentially without them interfering with each other in the changelog