Originally Posted by TobiSGD
cp -r $SOURCE $DESTINATION && rm -r $SOURCE
By the way, the GNU tools are open source, if you really need that function just because you don't want to use to commands for that functionality feel free to extent the mv command.
"cp -r $SOURCE $DESTINATION && rm -r $SOURCE" is not a good option when you want to move big directories between different computers, which take long and there might be interruption. you are right nevertheless, for the moment I complained so that if somebody is more expert and has the time to do it ;-).
This option is already implemented in nautilus, which is gpl licenced as well. It asks if you want to merge the folders or not, and there is a apply-to-all check-box. But one have to dig into the codes to transfer the functionality to the mv command