copies: filter out copies when target is not in destination manifest When chaining a series of commits that copied a file with a series that removed the destination file, we would still include the copy in the result. Similar to the previous patch, I have checked that `hg status --copies` is not affected by this bug, but I wouldn't be surprised if some commands are. Differential Revision: https://phab.mercurial-scm.org/D5989