option value cmd-completion like vim

[Song-Tianxiang]

In vim, if I enter :set background=<Tab>, I will get

But in neovim, I will get

How can I get option completion like vim in neovim?

I can get option completion but not option value completion in neovim.
In neovim, enter :set back<Tab> I can get

But I can not get background vaule compltion (dark and light) as above.

[zeertzjq]

Use nightly version.