mv: do not override destination file that is newer than source file (update move)

mv does not support the update option, unlike rsync and cp. If your version of coreutils does support it, using cp (followed by rm) is the easiest way to perform an update move operation:

$ cp -avu * [destination]
$ rm -rf *

Note that this will override only newer (by timestamp) files. It is not suitable for resuming a failed cp/ move. For this, you might use

rsync -va --append dirA dirB

instead. Note that dirA and dirB need to be present. See here for more details.