bug#13041: 24.2; diacritic-fold-search

[Drew Adams]

>  > We are using compatibility normalization, not canonical 
>  > normalization.  So a search (or a string comparison test)
>  > for `f' will match the ligature `ffi'
>  > (whereas it would not match wrt canonical normalization).
> 
> If it can be done, searching for "f" should match ligatures like "ff"
> and "fi".

That's what I thought you were planning/preparing to do.

On the other hand, as the Unicode spec points out (for level 2), sometimes
someone wants to distinguish searching for f from searching for the ligature.
Ideally (we might never get there), that would be possible as an alternative
(choice).

The spec also points to hybrid situations regarding case conversion (see sect
RL2.4) where, e.g., you might want to do full case matching on ß in a literal
name such as Strauß but simple case folding on ß when used in a character class,
such as [ß].  Dunno whether we would ever get there either.

There seems to be a lot in the Unicode regexp spec
(http://www.unicode.org/reports/tr18/) that could be food for thought for Emacs.
I imagine that some Emacs Dev folks have already taken a close look and given it
some thought.