bug#48657: Defvar delimiter for dired-copy-filename-as-kill

[Stefan Kangas <stefan@marxist.se>]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Rodrigo Morales <moralesrodrigo1100@gmail.com>
>> Date: Tue, 25 May 2021 14:12:02 -0500
>>
>> (defun dired-copy-filename-as-kill (&optional arg)
>> ...
>>              (mapconcat #'identity
>>                         (if arg
>>                             (cond ((zerop (prefix-numeric-value arg))
>>                                    (dired-get-marked-files))
>>                                   ((consp arg)
>>                                    (dired-get-marked-files t))
>>                                   (t
>>                                    (dired-get-marked-files
>> 				    'no-dir (prefix-numeric-value arg))))
>>                           (dired-get-marked-files 'no-dir))
>>                         " ") ;; <---- [[[ Here's the hardcoded delimiter ]]]
>> ...)
>> #+END_SRC
>>
>> I thought that it would be useful to have a defvar that allows
>> specifying the delimiter for copied filenames through the mentioned
>> function. Perhaps, its name could be "dired-copy-filename-delimiter".
>
> The only sane value for a reliable delimiter is the null byte, so
> maybe it doesn't make much sense to customize it.

That's true, but on the other hand replacing space with the null byte as
the hard-coded delimiter for dired-copy-filename-as-kill seems a
bit... clunky.  Even if space sometimes fails, it is not a control
character, which is why I assume that it was chosen.

I've personally never had a problem with using space here, but you
obviously will eventually run into problems.  So I think something
should be done.

I was thinking for a while about allowing a user to set the delimiter
with a prefix command, but then I realized that users might be using
this function *a lot* (I do sometimes) and that UI would quickly get
old.

So perhaps we should just provide the asked for defvar?