matched strings.
This way it is possible to choose one of the highlighted possibilities
without completing the search string (useful when using incremental
search for navigation).
The hints can be toggled on or off at any point during the search with
isearch-toggle-hints (which is mapped to C-f by default). Note that to
save keystrokes characters are used as hints instead of just numbers.

Anyway, please review it and if there is any interest in it merge it.

Thanks, Gideon.