feat(complete): group options by tag (in zsh)

[bobrippling]

This allows zsh to group completions by whether they're global, and then by their tag. For example:

$ dynamic -<tab>
completing "global" options
-v  -- --verbose
completing "Options" options
-F  -- --format
-h  -- Print help
-i  -- --input

Closes #6320

Outstanding Questions

Options name

completing "Options" options doesn't seem particulary nice, should we filter out the default "Options" tag?

clap/clap_complete/src/engine/complete.rs

Lines 532 to 534 in 1420275

	arg.get_help_heading()
	.unwrap_or("Options")
	.to_owned()

when generating the completions in shells.rs

Tests

My new test is currently failing because it gets the zsh initial login setup:

This is the Z Shell configuration function for new users,
zsh-newuser-install.
You are seeing this message because you have no zsh startup files
(the files .zshenv, .zprofile, .zshrc, .zlogin in the directory
/tmp/.tmpQxncRl).  This function can help you with a few settings that should
make your use of the shell easier.
[...]
Aborting.
The function will be run again next time.  To prevent this, execute:
  touch /tmp/.tmpQxncRl/.zshrc

I'm not sure why my test gets this but the others don't

[epage]

Does this mean we aren't getting the / handling if a tag is present?

[bobrippling]

The opposite in fact - if a / is there, we'll handle it (since we test that first) and only perform the option grouping for remaining options

[epage]

Items with / should still have grouping though

[epage]

What is : is in a tag?

[bobrippling]

I suppose we have two options:

• Pick a different separator - but what if that separator is in the tag?
• Avoid : in tags, either by filtering them out at this point, or making it part of the tag requirement

What do you think?

[epage]

We can pick an unlikely separator, like _SEP_

[bobrippling]

Thinking about it, I think we can avoid this entirely - I'll use the escape_value() function which looks to be for precisely this.

[epage]

This is redundant. In --help, we just list the header. We should likely do the same here as well.

[epage]

Why are these needed?

[bobrippling]

The format style is needed to have zsh show group descriptions - for example:

% ls -<TAB>
# ^ no option completions


% autoload -Uz compinit
% compinit
% ls -<TAB>
-@      -- display extended attribute keys and sizes in long listing                                                                                                                          
-1      -- single column output                                                                                                                                                               
-a      -- list entries starting with .                                                                                                                                                       
-A      -- list all except . and ..                                                                                                                                                           
...
# ^ options are shown

% zstyle ':completion:*:descriptions' format '%d'
% ls -<TAB>
option      # <----
-@      -- display extended attribute keys and sizes in long listing                          
-1      -- single column output                                                               
-a      -- list entries starting with .                                                       
-A      -- list all except . and ..                                                           
...
# ^ note that the "description" header is now shown, in this case a plain "option"

(group-name isn't needed so I've dropped it)