nushell: Ideas for better completion system

[bew]

Fallback completions / scripted completers

For typo corrections, any-case match, ..

Completion groups

I want more completion flexibility, inspired from zsh's completion system but with a
lot more structure thanks to nushell's structural data flow and manipulations.

Example of groups:

• for many commands: options, dirs, files
• for git checkout: modified files, local heads, remote heads, recent commit
• for cd: local dirs, recent dirs (session), recent dirs (any shells)
• for cd ~: named dirs, users
• for man: 1 group per man sections

I want to be able to:

1. Expose multiple completions groups
2. Have keybinds to navigate in a completion menu through the completion groups
3. Re-order the groups for some completions

IDEA: completion tags not groups
Completion items can have 1+ tags (?)
In results we can filter which results we want with #options, #path or !#git.untracked...

Notes

https://github.com/nushell/nu_scripts/blob/main/custom-completions/git/git-completions.nu has many
ideas, but AFAIK (NEED CONFIRMATION) it will put all results in the same list, and we can't see only
some completions

FIXME: export extern "git branch" [...] do not distinguish options & pos-param..

Results filtering: Fuzzy search / Search anywhere

TODO!

Results display: item format

To show some additional data about the item, e.g. as a prefix.
For example eza(-like) output with file size, number of changes hunk, ...

We could also show an icon before all local paths
compl_item_format: "<icon> <item><flex-align-spacing><description>"