On gum filter --no-limit --selected='*', only filtered lines should be outputed, or at least give an option to make the filter discard selections

[haumami]

Description

I understand that filter is meant ot be used as a search and mark logic,
but it is really useful as a pure filterer, and therefore,
I think it is counter-intuitive that on --no-limit --selected='*', when you press enter, all lines are returned instead of the filtered ones

Think for instance on a log file, you open gum filter, and expect to use it as an interactive grep, so only grepped lines are outputed.

I think this could be easy to implement but it would provde a whole new killer feature.
Perhaps we could add --selected='filtered' or either --unselect-currenlty-unfiltered