Toggleable prefix matching

[andreihh]

Feature Description

When typing and receiving ghost text suggestions, I expect the completion to be a strict continuation of what I typed, and to not change what has previously been typed. There should be an option that allows ghost text to disable fuzzy matching and use strict prefix matching instead.

As things are now, there ghost text suggestions can look a bit awkward / puzzling, considering that the completion menu is hidden and we don't see that it's based on a fuzzy match. In the following example, the target is DiffAdd rather than DiffChange, but with DiffA prefix, the ghost text is DiffAhange, which looks weird:

NOTE: I would still like manually triggered completion to use fuzzy matching and work just as it does now.

[saghen]

There's no easy way to do this with the existing architecture since the list is tied directly to fuzzy matching and we can't hot plug fuzzy matchers in. That's something I want to do for v2 though so stay tuned!

[saghen]

After some more thought, this definitely seems like the ideal behavior for ghost text, but I'm still not sure how I'll go about implementing it

[saghen]

Combining in #1721, this should also work for the menu. We need to be able to plug in fuzzy matchers and support re-running the fuzzy matching when the matcher changes.