doc: Update manpage a bit
doc: Update manpage a bit

I know, I know, it's about time...

resin-io/ostree,resin-io/ostree,resin-io/ostree,leandrosansilva/ostree,leandrosansilva/ostree,GNOME/ostree,gatispaeglis/ostree,gatispaeglis/ostree,leandrosansilva/ostree,sujitfulse/ostree,sujitfulse/ostree,sujitfulse/ostree,GNOME/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,resin-io/ostree,GNOME/ostree,gatispaeglis/ostree,sujitfulse/ostree,sujitfulse/ostree,leandrosansilva/ostree,resin-io/ostree,gatispaeglis/ostree,leandrosansilva/ostree,gatispaeglis/ostree