Add support to spawn the process about sudo-prompt

[jviotti]

Hi @jorangreef

I see :/ I certainly underestimated the amount of work needed. I'll take the tail approach as you suggested and see how far I can get with it.

I'll re-open this issue if needed, thanks a lot!

[jorangreef]

It is possible but would be a fair amount of work. Would be great if you could tackle it.

The Attempt() call is just the tip of the iceberg. That's there to try and run the command if a sudo session already exists, and if it does then that could be just a straight-forward spawn() instance passed back to the user.

But otherwise, the user command is run by a bash subshell which is called by the applet after acquiring administrator privileges. So we would essentially be trying to create a fake spawn() instance with all the same properties as a normal Node.js spawn() instance, but which wraps a bash subshell.

To understand how this works:

1. Add a console.log() statement to print out instance.path just after MacCommand() runs (https://github.com/jorangreef/sudo-prompt/blob/master/index.js#L196). This is the path to the temporary app created by sudo-prompt.
2. Before granting privileges, take a look at the logged path and then open it in Finder and make a copy of the temp app. The app will otherwise be deleted as soon as privileges are granted.
3. Open the app with Script Editor to view the Apple Script source, and then take a look in the MacOS directory within the app to see the bash scripts which are there.

If we can do this properly that would be great, but some aspects of the spawn() instance might be difficult to copy perfectly. Alternatively, it might be easier to write out your script's stdout and stderr streams to a file and tail those.