ostbuild: add --diffstat option for source-diff
ostbuild: add --diffstat option for source-diff

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