bug#62732: 29.0.60; uniquify-trailing-separator-p affects any buffer whose name matches a dir in CWD

[Eli Zaretskii <eliz@gnu.org>]

> Cc: sbaugh@janestreet.com, 62732@debbugs.gnu.org, sbaugh@catern.com
> Date: Wed, 12 Jul 2023 16:42:01 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > I can see 3 ways to provide this info:
> > 
> > 1- use `file-directory-p`.
> > 2- add a boolean `directory` argument to `create-file-buffer`.
> > 3- use the presence of a trailing directory separator in the filename.
> > 
> > Those 3 are very close to each other, in practice, so we're pretty much
> > in bikeshed territory.
> > 
> > My preference is (3) first, (2) second, and (1) last.
> 
> I prefer (1), because it avoids requesting the callers to remember to
> ensure that every directory ends in a slash.

So how about compromising on a variant of (2): we add an optional
DIRECTORY-P argument, and if FILENAME doesn't end in a slash, but
DIRECTORY-P is non-nil, create-file-buffer will append a slash?