[TxMt] Comment/Uncomment key?

[Chris Wong]

When I'm writting ruby code, I stumbled across Cmd-/, which
comments/uncomments out the selected blocked of code.

Where are all these hidden key-binding documented?  It's not in the
KeyBinding.dict that shipped with 1.1b17.

If I try to comment out the whole function below, it'd instead
uncomment the existing comment within the block.  I'd rather have
Cmd-/ always do comment-out, and Cmd-Option-/ always do the uncomment.
 Can I override the key-binding for the default comment/uncomment
behavior?

def foobar
   # comment inside function body
   do_something
end

Thanks for all your hard work.
Chris