Stop DirectoryWatcher from watching the destination directory

@svnpenn noticed that the change in 7457cbae2544b0b85beb118e3ca9b62bcb44d7f1 didn't actually fix the problem it was meant to. The mix of absolute and relative paths in the method caused the issue. I believe my fix here works and I added a couple tests to ensure the method runs as intended.

@mattr-, any input on the tests would be awesome. I'm used to Rspec's "describe-context" mix so the "context-should" was a bit awkward for me. :)