bug#27801: 26.0.50; Dired: Use relative file names when DIR-OR-LIST is a cons

[Tino Calancha <tino.calancha@gmail.com>]

On Sun, 23 Jul 2017, Drew Adams wrote:

>> ;; Following form shows the full file name in the Dired buffer.
>> (let* ((dir source-directory)
>>        (file1 (expand-file-name "lisp/subr.el" dir))
>>        (file2 (expand-file-name "src/data.c" dir)))
>>   (dired (list dir file1 file2)))
>>
>> ;; Usually, Dired just shows the relative file name to
>> ;; 'default-directory'.  That is more clear, specially for
>> ;; long file names.
>
> Sorry, but I've only read this bug report quickly - no time now.
>
> If you are suggesting that when DIR-OR-LIST is a cons the
> file names shown should be relative then I think I disagree
> strongly.
>
> The typical use case for a cons DIR-OR-LIST is a list
> of files from anywhere, in which case absolute file
> names are appropriate.
I am OK with adding a new variable `foo' so that i can get
this behavior if i locally bind `foo' to a non-nil value.

This idea comes while i am trying to implement Bug#27631; to
have this feature working with 'ls-lisp' my implementation
do something like:

1) Collect all matches with `find-lisp' in a variable FILES.
    (This is just a first approach to the problem; for large
    number of matches would be better to not store the matches
    in a list).

2) [Suppose DIR is the default-directory i the Dired buffer]
    Then call:
(dired (list DIR FILES))

;; My implementation works as with GNU ls; the only difference is
;; that 2) shows full file names in the Dired buffer.  I rather
;; prefer is the output has same format regarless on if the user
;; use `ls-lisp' or not.

With the var `foo' mentioned above, we could change 2) with:
3)

  (let ((foo t))
    (dired (list DIR FILES)))