#81 Copy should be able to "merge" into existing top-level destination

[Emil Brink]

When copying a big hierarchy of files, if the top-level directory exists in the destination, gentoo will ask what to do to handle the collision. Unfortunately, there is no "merge" option, all you can do is continue (which will delete the existing directory first) or skip.

Often when doing really big copies, you need to stop and re-start the copying several times due to ... things, and of course it's not ok to delete all you've done when re-starting.

Please fix.