Suggestion: Prompt & Handling magnet links

[thanosapollo]

Thank you for making this package.

Some changes I personally believe would improve the user experience:

Adding custom variables such as :

• Default directory to look for .torrent files to add; transmission-torrents-dir
• Default download directory; transmission-download-dir

I'm using those var names as an example for reference

Changing transmission-add in the following ways

• Detect magnet links from clipboard & add them as an option to the directory-files of transmission-torrents-dir
  • Current prompt implementation works nicely with packages like ivy, but without ivy or with packages like vertico, there is no way as far as I know to select the magnet link

From a quick look at transmission.el maybe something like this would be useful:

(defun transmission-add--prompt ()
  "Add magnet link from clipboard or prompt for torrent file."
  (let ((clipboard (gui-get-selection 'CLIPBOARD)))
    (if (and (>= (length clipboard) 6)
             (string-equal "magnet" (substring-no-properties clipboard 0 6)))
        (completing-read
         "Add torrent: "
         (cons clipboard (directory-files transmission-torrents-dir t "\\.torrent$")))
      (read-file-name "Add torrent: " transmission-torrents-dir))))

Something like the scratch function above could be used as the input of transmission-add, simplifying it's current implementation as well.