bug#20195: 25.0.50; Let Dired commands such as `dired-do-search' (`A') use prefix arg

[Drew Adams <drew.adams@oracle.com>]

> >   If ARG is a cons with element 16, 64, or 256, corresponding to
> >    `C-u C-u', `C-u C-u C-u', or `C-u C-u C-u C-u', then use all files
> >    in the Dired buffer, where:
> >      16 includes NO directories (including `.' and `..')
> >      64 includes directories EXCEPT `.' and `..'
> >     256 includes ALL directories (including `.' and `..')
> 
> Isn't it simpler to mark all files in a subdir (`* s') or just toggle
> everything with `t' and then invoke the command?

That's already available.  Nothing new about that.  Useful, of course.

The point is that you might currently have markings that you want to
keep for a while, and you want to perform an on-the-fly operation on
all files, without fiddling with any existing markings.

IOW, this is an additional possibility.  It takes nothing away from
what you can already do.  In particular, it does not change the behavior
of a single `C-u' (that still acts on the next 4 files, just like `C-4').

> A movement command

I don't think there has been any mention of any movement commands.
What did you have in mind?

> is ok to take argument specifying a number of files,
> because that number is related to that command's main purpose.  But here
> files are collected according to marks set in the buffer, so it's kind
> of duplication to provide the same functionality via prefix argument.

See above.  There are *many* ways to do the same thing in Dired (and
elsewhere in Emacs).  In and of itself, eliminating such "duplication"
is a silly goal (IMHO).

And it is already the case that a numeric prefix arg acts on the next
(or previous) N files, ignoring any existing marks.

To be clear:

1. I don't really care whether Emacs adds that feature (multiple `C-u'
acts on all, ignoring markings).  And that feature is not what this
enhancement request is about.

2. As one user, I use that feature quite often (with Dired+).  If
you don't find it useful, and you prefer to always mark and unmark,
that's fine by me. ;-)