Fix :Hgvdiff with a file that is a copy. Previously, :Hg rename old new :" (A rename is a copy and a deletion of the file with the old name.) :edit new :Hgvdiff " "new: no such file in rev NNNN" was displayed in the window to the right of the new vertical split. Now :Hgvdiff diffs new with old from the head revision.