I'm trying to make the game run two commands on a keypress - I've already set up the key, created a packet for running the commands and am calling performCommand() inside that. The only thing I seem to be missing is that I have no idea what I'm supposed to provide for the CommandSourceStack the method wants (doesn't help that nothing is documented)

So so far I have

ctx.get().getSender().server.getCommand().performCommand(??,"say hi"); //(just as a test (dunno if I need a / or not here))

inside the packet - the ?? being the CommandSourceStack it wants. (Even if I just do new CommandSourceStack() the constructor wants a variety of things which I have no clue about.) So, what do I need to put there?

you can use ServerPlayer#createCommandSourceStack

Thanks for letting me know! 
Is there any reliable way for finding methods like this or do you kinda just have to.. know them? Since none of the forge classes have documentation as far as I could tell.