bug#21140: 25.0.50; Isearch "char-fold" by default

[Sebastien Vauban]

Using Isearch under Emacs 25.0 really puzzles me.

First, the default behavior seems changed, and I'm not really aware
(yet) of what exactly "char folding" is.  I did not found any definition
for this, even if I have some ideas.

Second, I don't think the new default is right.  I prefer to search for
text, not for regexps by default.  Otherwise, we could also invert `C-s'
and `C-M-s', right?

Finally, it *seems* buggy to me when using `C-w' to complete the search
pattern (or shouldn't we use that anymore?).

Try it with the following example:

--8<---------------cut here---------------start------------->8---
  ;; some function
  (turn-on-orgstruct++)

  ;; other function
  (anzu--turn-on)
--8<---------------cut here---------------end--------------->8---

As you can see on http://www.screencast.com/t/wx7r9UYK:

- Completing "turn" with `C-w' will go over the 2 last "+" signs as if
  they did not exist. In Emacs 24, each "+" char was added one by one.

- Completing "anzu" with `C-w' will simplify the 2 "-" signs as being
  just 1, making the search find no string at the end!

- Completing "zu" with `C-w' will add "zu" to the pattern, multiple
  times...

Isearch becomes quite complex to use IMHO.

PS- BTW, Anzu seems completely lost in Org files, when now run from
    Emacs 25.

Best regards,
  Seb

-- 
Sebastien Vauban