>> After using this for a while I noticed that most of the time
>> mailcap suggestions are useless - they don't contain the same
>> items as in the context menus of a File Manager.  For example,
>> clicking the right mouse button on a ScreamTracker .stm file
>> opens a menu with Rhythmbox, and clicking on a ScreamTracker3
>> .s3m file opens a menu where the first item is Celluloid
>> and the second is Rhythmbox.
>>
>> So I implemented support for xdg commands that now displays exactly
>> the same menus in Emacs as in the File Manager, and with the same order.
>
> Agreed, it's better to use the xdg commands for this.

Here is a new patch that uses a new generalized function
'shell-command-guess' from bug#18132: