Fix wrong unit when split string

[petricavalry]

Fixes #837.

reedline/src/menu/columnar_menu.rs

Line 305 in 4634f71

let (match_str, remaining_str) = suggestion.value.split_at(match_len);

split_at expect byte offset.

reedline/src/menu/columnar_menu.rs

Line 302 in 4634f71

let match_len = self.working_details.shortest_base_string.width();

But we given (got from width) isn't.

Thanks for all amazing works in reedline.

[sholderbach]

Yeah for anything involving string splitting .len is the relevant thing to get to the indices, while .width serves as a best guess for the layout width in the terminal. We need to be sure that the right thing is used in the right place.

There seems to be some preexisting history of display bugs leading to this

• Column menu spaces don't respect special characters (accents, emojis...) #793
• Fix #793 using width() for column menu alignements with special char #794

[petricavalry]

I'm not sure but I can't reproduce #793. match_len is used to split string only. It seems to have been modified incorrectly by #794 and cause this issues (#837).