Added support for softwareupdate --fetch-full-installer and seedutil for clients running macOS 10.15 or greater.
Run with --fetch-full-installer option to use softwareupdate instead of installinstallmacos.py to obtain your installer. Most modes are still compatible with this option, such as --overwrite, --reinstall, --erase. --move is not supported with this option at this time: the installer will be downloaded straight to /Applications.
When the --seedprogram option is used, the script will change the seed program using seedutil. At this time, it does not revert the seed program setting after use, so bear this in mind. The output shows which seed program you are in.