manifest: for diff(), only iterate over files, not flags From manifest.diff(), we return a dict from filename to pairs of pairs of file nodeids and flags (values of the form ((n1,n2),(fl1,fl2))). To create this dict, we currently generate one dict for files (with (n1,n2) values) and one for flags (with (fl1,fl2) values) and then join these dicts. Missing files are represented by None and missing flags by '', but due to the dict joining, the inner pairs themselves can also be None. The only caller, merge.manifestmerge(), then unpacks these values while checking for None values. By inlining the calls to dicthelpers and simplifying it to only iterate over files (ignoring flags-only differences), we can simplify life for our caller.