bug#62621: 29.0.60; uniquify can't make buffers unique based on things other than filename

[Eli Zaretskii <eliz@gnu.org>]

> From: Spencer Baugh <sbaugh@janestreet.com>
> Cc: Dmitry Gutov <dmitry@gutov.dev>,  sbaugh@catern.com,  62621@debbugs.gnu.org
> Date: Wed, 19 Jul 2023 08:31:00 -0400
> 
> >> >>> Repeat after me: Use options whose values are functions
> >> >>> are hard on our users, because they require them to be Lisp
> >> >>> programmers.
> >> >> That doesn't have to be the case. If the defcustom's docstring mentions
> >> >> several functions that can be used, and the :type widget includes them
> >> >> as well, the user can decide to switch to any of them without writing
> >> >> any Lisp (or having to understand the implementations).
> >> > But that was not so in this particular case.
> >> 
> >> That's easy to fix, as long as you don't have additional objections to 
> >> that approach.
> >
> > I'd need to see the fix first, because I don't think I have a clear
> > idea of what you have in mind.
> >
> > (My objections, btw, where very minor and of pure usability nature.
> > Frankly, I'm surprised such a simple and more-or-less agreed-upon
> > comment got such a long thread of discussing various loosely-related
> > issues.)
> 
> Like this:

Thanks, but it still falls short of what Dmitry described above: the
doc string doesn't "mention several functions that can be used".

> +(defcustom uniquify-dirname-transform #'identity
> +  "Function to transform buffer's directory for uniquifying its name.
> +
> +It takes a single argument: the directory of the buffer.  It
> +should return a string filename (which does not need to actually
> +exist in the filesystem) to use for uniquifying the buffer name."

Please read this carefully and try to put yourself in the shoes of a
user who needs to make sense out of this description.  The immediate
question I had is what does "transforming a buffer's directory" have
to do with "uniquifying the buffer name"?  Uniquifying a buffer's name
is not about its directory, at least not in general.  IOW, the
starting point of this description is too "inside" the implementation.