x11-autologin: detect default lightdm session

features.in/x11-autologin/rootfs/image-scripts.d/40-x11-autologin

@@ -55,9 +55,11 @@ fi
 LIGHTDM_CONF=/etc/lightdm/lightdm.conf
 if [ -f "$LIGHTDM_CONF" ]; then
 	backup "$LIGHTDM_CONF"
+	default_session="$(ls -1 /usr/share/xsessions/*.desktop | sed -n 's/^.*\/\([^/]\+\)\.desktop$/\1/;1p')"
 	sed -i \
 		-e "s/^#\(autologin-user=\).*$/\1$USER/" \
 		-e "s/^#\(autologin-user-timeout=0\)/\1/" \
+		-e "s/^#(autologin-session=).*$/\1$default_session/" \
 		"$LIGHTDM_CONF"
 	backup "/etc/group"
 	add_nopasswdlogin_group lightdm ||: