Allow slightly more complex actions in the context menu

[GoogleCodeExporter]

I would like to add an action item like this:

  dirname "FONTPATH" | xargs xdg-open

But I can not find a way to do this since (1) Executable and Arguments are two 
different fields and (2) FILEPATH automatically gets added to the arguments.

I have tried using a hash (#) to comment out the FILEPATH as well as using 
variables, to no success.

Is there a way to currently make this work?

Otherwise, perhaps FONTDIR could be added as a magic constant which, when used, 
silences the automatic use of FILEPATH in the arguments. Or some other solution.

Original issue reported on code.google.com by vargavind@gmail.com on 22 May 2015 at 7:49