oups sorry these changes last from such a long time that I was making a mistake about their reasons:
in the version of Fugue I have been using `--unmaskfmap` and `--unmaskshift` does not allow file specification, they just modify the output of the files specified by `--savefmap` and `--saveshift`, they are boolean options. So these changes was to reflect the real functioning of the Fugue binary. So I did also separated the outputs into forward and standard unwarping.