If folder already exists

[calee0219]

move folder to .bkg if folder already exists
(not test yet)

[sufuf3]

Thank you.
However, when I ran the command like cd ~/ && mv -r protobuf protobuf.bkg && git clone https://github.com/google/protobuf.git, I met the following situation.

mv: invalid option -- 'r'
Try 'mv --help' for more information.

Because there is no protobuf under ~/.
Maybe we have to add a checker to check if there is the same name folder.
What do you think?

Thank you very much.