bug#47599: 28.0.50; Feature request improve/update isearch

[Juri Linkov]

> Just to follow this:
> https://lists.gnu.org/archive/html/emacs-devel/2021-04/msg00080.html
>
> I open a feature request to suggest some updates in the isearch code and
> the addition of some simple functionalities like:
>
> 1) Option or command to automatically go to the other end on exit.

It seems the conclusion was that it should not be an option.
As for a command, there were objections against binding it to a key,
but without a keybinding such command has little sense.

> 2) Convert isearch-wrap-function,

Thanks for the suggestion.  Customization of wrapping was implemented now
by the new option 'isearch-wrap-pause'.  It also handles numeric arguments
of 'isearch-repeat'.

> isearch-push-state-function,
> isearch-filter-predicate into customs instead of use defvar, improve a
> bit their documentation and provide some handy options.

These functions are intended to be modified by modes, not by users.

> 3) Make some general refactor of isearch code to simplify and remove
> some redundant or useless checks, vars and code. Update the code to use
> some useful modern api like define-minor-mode or easy-mmode-defmap. There
> are some external packages that reimplement the isearch
> functionalities or hack it to produce some of these
> functionalities/behavior and maybe (as an extra) we could consider add
> some customs to make isearch behave like a bit like that; because most
> of them are not very different to what isearch already does now.

Rewriting isearch is a huge and unnecessary task.

More patches were posted directly to emacs-devel now,
so more changes are expected from that discussion.