Add support for history isearch

[gcv]

Incremental history search is very powerful, and it would be great if Selectrum supports it. So for example, C-x C-f would start a Selectrum-enabled file dialog, and C-r would search through file-name-history (or whichever history variable is appropriate for the given command). It would be especially great if the incremental search candidates could be shown in the Selectrum candidate narrowing display.

[raxod502]

Let me know what you think.

[clemera]

selectrum-select-from-history works great for me and I like that selecting the history element exits both recursion levels at once. If that was by accident I think this should be considered a feature not a bug. But for the general case selectrum should only exit the last recursion level.

[raxod502]

That's intended, and indeed in the general case only one recursion level is exited.

[clemera]

I see, nice! selectrum--exit-with runs twice though which means selectrum-candidate-selected-hook runs twice.

[gcv]

Excellent!! Thank you, this works really well.

[raxod502]

selectrum--exit-with runs twice though which means selectrum-candidate-selected-hook runs twice.

True; it's arguable either way whether this makes sense or not. (Another interesting question is "should the selected candidate from history selection be itself added to history, and if so which one?" Currently the answer is that we add it to minibuffer-history, because that was the most elegant thing to do in the code.)

[clemera]

should the selected candidate from history selection be itself added to history, and if so which one?

Good question, I think we should let bind minibuffer-history-variable and the hook so the selection of the history element within the history completion is ignored and has not state effects. That way it is just a helper to select an element from the original completion. The original completion should treat it like any other selection the user has done.

[raxod502]

Okay, that's reasonable. Want to make a pull request for that?

[clemera]

Sure, just has to wait a few days probably.

[clemera]

Done #72