What to do when `mesh_mask.nc` does not exist?

The preprocess_orca() function needs a mesh_mask.nc-file. But sometimes mesh and mask variables are saved in separate files (mask.nc, mesh_hgr.nc, mesh_zgr.nc). So there is two possibilities. 1: add some lines to the xorca module to take that into account, or 2: the user has to combine the separate files into one mesh_mask.nc before using xorca...