bug#40216: 28.0.50; Misinformation in isearch char-fold

[Robert Pluim]

>>>>> On Thu, 26 Mar 2020 16:25:14 +0200, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Robert Pluim <rpluim@gmail.com>
    >> Date: Thu, 26 Mar 2020 10:28:55 +0100
    >> Cc: 40216@debbugs.gnu.org
    >> 
    >> Do we need an option to char-fold-regexp that says 'only apply
    >> char-folding to non-ascii characters'?

    Eli> But this feature is not intended only to find variants of non-ASCII
    Eli> characters when one searches for a non-ASCII, it is also intended to
    Eli> find variants when searching for ASCII characters.  For example,
    Eli> searching for a is supposed to find ä and à and á.  Or am I missing
    Eli> something?

Yes, thatʼs exactly right. But in the case where you have mainly
characters where you donʼt want case-folding, it might make sense to
restrict the folding to non-ascii as an optimisation. eg. Suppose my
name were Røbert, with people frequently misspelling it as Robert, I
might want isearch to just search for "R\\(?:ǿ\\|[øǿo]\\)bert"

Røbert