docs: list --why as a suboption of --tree in poetry show

[kosmv]

Hi!
Here's my attempt for #5625

[tgolsson]

See my comment on original issue; the docs are unclear but this is even less correct. :-)

[Secrus]

@kosmv thank you for your contribution.

@tgolsson Can you please assist with clearing up how this should work? its cool feature, but in my testing it was hard to find how it should be used. Thank you in advance.

[github-actions]

Deploy preview for website ready!

✅ Preview
https://website-2c9gkr47f-python-poetry.vercel.app

Built with commit b8b8a56.
This pull request is being automatically deployed with vercel-action

[kosmv]

@tgolsson Oh right, my bad. I didn't understand why --why can be used alone.

[tgolsson]

@Secrus Unless @kosmv wants to finish this I'll make a PR tonight :-)

The intended behavior is as follows:

• You can use --why when showing table or when showing a tree for a single package.
• If you use --why for the table it'll include a from a, b, c column
• If you use --why for a single-package tree it'll root the tree at the parent packages instead of the queried package.

This comment contains the expected two use-cases: #5444 (comment).

The CLI command line is just utterly wrong; I think I had some rebase problems and didn't double-check that well enough. The docs one should probably just specify where it's applicable and not just "when applicable".

[kosmv]

@tgolsson Sorry for not reading your original pull request properly.
My terminal width was reduced, so I couldn't see the from package-name column when I tried your feature.

I won't finish this, you can make your PR :)

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.