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

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 62621@debbugs.gnu.org
> From: sbaugh@catern.com
> Date: Thu, 13 Jul 2023 22:51:53 +0000 (UTC)
> 
> I've thought quite a bit about how to make this configurable, and I
> think just letting people write their own arbitrary transformation
> functions, as I do in this patch, is what we should provide.  Making
> things any more modular is fairly difficult.  Packages can come along
> and provide other fancy functions if they like.

If there are a couple of simpler alternatives which could be offered
via simple symbolic values, we should not force everyone to write
functions, IMNSHO.  IOW, we should NOT immediately generalize to
functions only because such generalization could make sense in some
use cases.  Repeat after me: Use options whose values are functions
are hard on our users, because they require them to be Lisp
programmers.

> +(defcustom uniquify-dirname-transform #'identity
> +  "A function to transform the dirname used to uniquify a buffer.

"Function to transform buffer's `default-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."
> +  :type '(choice (function-item :tag "Don't change the dirname" identity)
> +                 function)
> +  :group 'uniquify)

The :version tag is missing.

Also, the doc string should state that the default is to use the
buffer's default-directory without any transformations.  It should
also include a link to uniquify-buffer-file-name, so that users could
consult the uniquify facilities if they need to.

Thanks.