I would like to move a directory and all its contents ontop of another.
By this I mean, that if I have two directories, A and B and I want to move B onto A, I want files and directories that are not in A but are in B to be simply copied across to A, files of the same name in A to be updated to the copies in B, and folders of the same name in A to be updated with new contents from B but otherwise have existing contents retained
Is there a way to do this easily in bash?
Incidentally, it is my understanding that this is what happens when you extract a tar archive over an older version of that archive. Is this true?