cmdutil: fix newandmodified file accounting for --interactive commits `originalchunks` is a misleading name, because it only contains header objects, which are flattened to selected hunks by the filter function. As such, `chunks not in originalchunks` is always True and misleading, because hunk objects never compare equal to header objects. This change fixes the internal naming and removes the useless parameter from the method. This change also fixes issue6533, by considering the filtered headers, rather than the hunks, when determining new and modified files. If a file is renamed + edited, and the edited hunks are deselected (but the file is not), the filtered chunks will contain a header for the file (because it's .special()) but but no hunks. Differential Revision: https://phab.mercurial-scm.org/D10936