Add custom completion for :Glaive

[glts]

I suspect you will want to add this sooner or later, might as well have an issue on the issue tracker!

Basic custom completion for a :command is easy to add but tremendously helpful for the user.

:Gl<Tab>
:Glaive 
:Glaive myp<Tab>
:Glaive myplugin 

and perhaps even

:Glaive myplugin som<Tab>
:Glaive myplugin somesetting

More info at :h :command-completion.

[dbarnett]

Indeed, I'd been wanting completion for :Glaive and just forgot to file a bug for it after moving to github. I also just filed #9 for adding a mechanism to query the current flag values, which is very related and might get done at the same time.

Contributions very welcome here. It's something I'd love to see but haven't had time to work on.

[glts]

I spent a short while looking into this for fun.

I wonder why you chose to make the notation different from Vim's notation.

:set list             :Glaive plug list
:set nolist     vs    :Glaive plug !list
:set list!      vs    :Glaive plug ~list
:set invlist    vs    :Glaive plug ~list
:set list?      vs    TBD
:set list&      vs    N/A

Is there a technical reason for this? I think acceptance would be better if users could apply the same pattern as in standard :set.

[dbarnett]

Good point. I raised the question separately in #12. I'd like to hear what @Soares thinks about it.