copies: correctly skip directories that have already been considered Previously, `if dsrc in invalid` would never be true, since we added `dsrc +"/"` to invalid, not `dsrc` itself. Since it's much more common for individual files (not whole directories) to be moved, it seemed cleaner to delay appending the "/" until we know we have some directory moves to actually consider. I haven't benchmarked this, but I imagine this is a mild performance win. Differential Revision: https://phab.mercurial-scm.org/D4284