Document the --file-forwarding option
Document the --file-forwarding option

This commit also documents the handling of rest arguments.
Previously, there was no information about what happens to ARG...

matthiasclasen/flatpak,flatpak/flatpak,GeorgesStavracas/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,matthiasclasen/flatpak,GeorgesStavracas/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,GeorgesStavracas/flatpak,flatpak/flatpak,handsome-feng/flatpak,handsome-feng/flatpak,flatpak/flatpak,handsome-feng/flatpak,GeorgesStavracas/flatpak,matthiasclasen/flatpak,flatpak/flatpak