bug#16493: 24.3.50; (setq search-invisible t) is useless, let's allow to turn visible-mode temporarily on

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@gmail.com>
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>,  bzg@gnu.org,  
> 16493@debbugs.gnu.org
> Date: Wed, 01 May 2019 07:40:31 -0400
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Stefan Monnier <monnier@iro.umontreal.ca>
> 
> >> PS: To fix this quirk, we should change buffer-invisibility-spec's
> >> default value to nil (or `(t)`, maybe) instead of t.
> 
> (t) makes sense, I'd say.

The difference (or lack thereof) between t and (t) is something that's
confusing, and should be preferably avoided.

> It's not a change to semantics though, just the default value.  And
> starting from the current default of t, if some code does
> (add-to-invisibility-spec 'foo) followed by
> (remove-from-invisibility-spec 'foo) you get (t), so arguably just
> starting from there in the first place makes things less confusing than
> they are now.

I'd rather we fixed the remove-from-invisibility-spec result than
start promoting (t).