bug#44901: 28.0.50; dired-compress-file: provide customization for compressing command

[Jean Louis]

In the function: dired-compress-file there is hard coded gzip as
compressor:

(dired-check-process (concat "Compressing " file)
                        "gzip" "-f" file))

It would be useful to have customization as there are various other
compressors that are often used to distribute files such as these, and
all of them supprot -f option:

- bzip2
- xz
- lzip
- there may be others

Customization option could be called dired-compress-command or
similar and it could default to gzip 

(defcustom dired-compress-command "gzip"
  "Default compressing command for dired. The commpressing 
command shall support the option `-f' to force overwriting the file"
  :type 'string
  :group 'dired)

Then the part here in the function `dired-compress-file' can be changed to:

(dired-check-process (concat "Compressing " file)
                        dired-compress-command "-f" file))


Thanks,
Jean Louis
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