refactor the handling of the filename arg to make consistent
refactor the handling of the filename arg to make consistent

...across load, insert, and apnd commands.

anba8005/melted,zzhhui/melted,zzhhui/melted,mltframework/melted,anba8005/melted,zzhhui/melted,anba8005/melted,anba8005/melted,zzhhui/melted,mltframework/melted,zzhhui/melted,mltframework/melted,mltframework/melted,mltframework/melted,anba8005/melted,zzhhui/melted,anba8005/melted,mltframework/melted