Add option to show completion at start on Prompt.Input()

[rhysd]

I'm using this library for Prompt.Call to choose one from several candidates.

The pain point for me was no completion window is not shown at start. Users cannot notice that it supports completion until they input first character. However, in context where users choose one of candidates, they need to know what character should be input at first. However they can't since there is no candidate shown at start.

So I added one small option OptionShowCompletionAtStart to show completion just after starting selection, which is disabled by default. I could not add any test for this since there is no test for prompt.Input and prompt.Option*.

I've just started to use this library. So it may be possible to do that without adding a new option. In the case, I'll be happy if you kindly tell how to do that.

[c-bata]

Sounds reasonable and enough simple to merge this 👍

Hopefully, options are used as unified regardless of using prompt.Input or prompt.Run. So I think it's better to add if p.completion.showAtStart { p.completion.Update(*p.buf.Document()) } before following line if there isn't something reason why you didn't add this.

go-prompt/prompt.go

Line 54 in dab0b55

p.renderer.Render(p.buf, p.completion)

[rhysd]

Sure. I'll update this branch. Thank you for your review.

[rhysd]

I updated my patch by ammending the first commit. I also rebased this branch onto the latest master.

[c-bata]

Thanks. I confirmed this works fine.