bug#28439: suggestion: support case-independent xref-find-definitions prompt TAB

[Eli Zaretskii <eliz@gnu.org>]

> Cc: wbe@psr.com, bug-gnu-emacs@gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 19 Sep 2017 03:55:34 +0300
> 
> On 9/14/17 8:01 PM, Eli Zaretskii wrote:
> 
> >> Sorry, what don't we want to follow the value of completion-ignore-case?
> > 
> > Because it has a much broader effect. 
> 
> I guessed so. But do you have a particular problem in mind?

No, just a general concern.

> > Then maybe an alternative is to make tags-case-fold-search nil by
> > default? Or make xref--read-identifier be case-insensitive if
> > case-fold-search is non-nil?
> 
> The other way around: etags--xref-find-definitions can bind 
> tags-case-fold-search to the value of completion-ignore-case. Or 
> whichever xref-specific variable we add.

Fine with me.

> We'd also need to add case-insensitive search support to 
> elisp--xref-find-definitions, I suppose. So far, 
> find-function-search-for-symbol always performs case-sensitive search. 
> It's rarely a problem, though, because Elisp uses capital letters very 
> infrequently.

Agreed, on both counts.

> >> Maybe we could add a similar xref-specific option on top, but I'm not
> >> sure why completion-ignore-case is not good enough.
> >>
> >> We could change its default to t, though.
> > 
> > Emacs-wide?  Or just when completing on identifiers?
> 
> Either is fine, as far as I'm concerned.

Emacs-wide is too radical, I think, and I don't think we have a good
case for justifying that.

Thanks.