Adding a script to MacOS finder contextual menu

Question

I want to add an option to the finder context menu that calls hg add %1 with %1 being the full path of the selected file in finder.
Of course there are more useful cases I can think of, to add to the context menu.
Is there a simple way to do that which doesn't involve installing any 3rd party software or coding in a compiled language and building binary plugins?
Like creating a script with the script editor and dropping it in /Library/Contextual Menu Items/ ?

Answer 1

Yeah, I know this is third party software - but for the sake of a fuller overview - http://www.abracode.com/free/cmworkshop/on_my_command.html. Another tool that would make your script writing easier is http://wafflesoftware.net/thisservice/ adding items to the service menu.