Can a link in a node setup be temporarily disabled? To debug a messy material node setup in Cycles, I want to remove one link between certain nodes, then restore it when I'm done putzing around.  Being absent-minded, I don't trust myself to remember.  

Is there some easy way to turn off a link temporarily, making it as if it weren't there,  without actually deleting it?

Whatever trick there is to do this, it should be visually obvious, so I can see that the link is disabled.

I'm using Cycles for materials right now, but I assume what I'm trying to do could apply to anything using a nodes editor.
press m to mute (disable) the node