bug#18132: Time for a smarter dired-guess-shell-alist-default? (dired-x.el)

[Juri Linkov <juri@linkov.net>]

>> -   '("\\.dvi\\'" "xdvi" "dvips")	; preview and printing
>> -   '("\\.au\\'" "play")			; play Sun audiofiles
>> -   '("\\.mpe?g\\'\\|\\.avi\\'" "xine -p")
>> -   '("\\.ogg\\'" "ogg123")
>> -   '("\\.mp3\\'" "mpg123")
>> -   '("\\.wav\\'" "play")
>> -   '("\\.xbm\\'" "bitmap")		; view X11 bitmaps
>> -   '("\\.p[bgpn]m\\'" "xloadimage")
>> -   '("\\.gif\\'" "xloadimage")		; view gif pictures
>> -   '("\\.tif\\'" "xloadimage")
>> -   '("\\.png\\'" "display")		; xloadimage 4.1 doesn't grok PNG
>> -   '("\\.jpe?g\\'" "xloadimage")
>> -   '("\\.pdf\\'" "xpdf")
>
> Thanks.  However, to justify such significant changes in this
> database, we need much more details: we need to know, for each guess
> you want to disable or delete, when and on what platform(s) is or was
> it true, when and why and on what platform(s) it stopped being true,
> and what replacement(s) are available on modern platforms for those
> commands that are no longer useful guesses.

Do you really think it's possible to get a list of all popular commands
available on all platforms?

> And if the guesses you are removing are supposed to be guessed better
> by XDG, then we should do that in a way that still supports systems
> without XDG.

This is just a random list of arbitrary commands.
And the problem is that dired doesn't check with 'executable-find'
if any of them is really installed.

But OK, if you want 100% backward-compatibility,
I will refactor out this list of obsolete commands
into a separate variable used by default.
Then a new value of existing option will allow omitting it.

> We cannot make such changes based only on your personal experience on
> the system which you use, because we don't want to break other users'
> setups.  So we must have these details to make this kind of decisions.

I don't know where you get such an idea that it's based
on my personal experience.  For my use I customized
dired-guess-shell-alist-user long ago.

Instead of this I'm addressing multiple complains.
Here is just a few after a very quick search,
I remember there were much more:

https://lists.gnu.org/archive/html/bug-gnu-emacs/2008-06/msg00202.html
https://lists.gnu.org/archive/html/bug-gnu-emacs/2021-10/msg01952.html