merge: copy fixes and tests
Fix up "already seen" logic
Fix merge action in remote copy case
Add status message
Add lots of merge+copy/move test cases
Is there an error message when trying to diff non-existing files?
found: No such file or directory
not: No such file or directory
Is there an error message when trying to add non-existing files?
found: No such file or directory
not: No such file or directory