largefiles: reduce redundant splitstandin/standin combination assumptions: - 'lfutil.splitstandin(f)' strips 'f' of '.hglf/', if it can - 'lfile(f)' examines 'lfutil.standin(f) in manifest' - 'lfutil.standin(f)' adds '.hglf/' to 'f' and - 'f' should start with '.hglf/' there, because it is already examined by 'lfutil.isstandin(f)' then: lfile(lfutil.splitstandin(f)) => lfile(<f without '.hglf/'>) => lfutil.standin(<f without '.hglf/'>) in manifest => <<f without '.hglf/'> with '.hglf/'> in manifest => f in manifest