bug#22829: Acknowledgement (25.1.50; Display number of marked files)

[Juri Linkov]

> I have included the subdir sizes as an option: currently the subdir sizes are
> not computed by default. We can change this behaviour to the opposite,
> with subdir sizes computed by default, after the code being well tested.

Thank you!  I have a feeling that code could be optimized more before
installing to dired.  I'll check it to estimate how well it works.

One quick comment: in defcustom my-dired-used-space-program
you could find if an executable exists like:

(defcustom my-dired-used-space-program (and (executable-find "du") du")

For more examples, please see defcustom dired-chown-program or
defcustom archive-zip-extract how to define a command
with its arguments in one defcustom.

> There are two functions doing the same thing:
> * my-dired-count-sizes-opt1:
> * my-dired-count-sizes-opt2: This looks nicer but it requires cl-lib.

dired-aux.el already includes (require 'cl-lib) - twice (just in case :),
so there is no problem in using 'cl-lib.