Support lowercase matched auto completion

[TheWaWaR]

First, thank you for your really cool project : )

The doc of Completer::complete says:

Returns the set of possible completions for the prefix word.

As I understand, it only support prefix based auto completion. However, if auto competion support lowercase matched candidates would be more cool.

Suppose we have subcommands below:

• count
• checkout
• branch

If we type ou, the matched candidates will be count and checkout.

[murarth]

Prefix matching is only the convention. You can implement a Completer that returns completion candidates based on any arbitrary criteria.

[TheWaWaR]

Wow! It actually works!

I tried this before, just not realized it works that way. If the word is not a prefix then it just disappeared, the candidates shows up correctly though. Not the way zsh (or maybe oh-my-zsh) auto completion works.

[murarth]

Well, linefeed does expect that the completion candidates will have a common prefix (though it does not require this to be true). The current word is replaced with that prefix. How does zsh do it when there's no common prefix?

[TheWaWaR]

These are candidates of git ou

[murarth]

@TheWaWaR: Wow, that is elaborate. I don't envision linefeed natively implementing a completion function that looks like that, but if one wanted to implement a similar completion interface as a Command trait implementation, I believe it would be possible.