cli: add help

kroko-cli.sh

@@ -23,6 +23,20 @@ _echo_err(){
 	echo "$@" 1>&2
 }
 
+_echo_help() {
+	echo "
+Usage: $0 [ get-gpus | best-driver | autoinstall ]
+get-gpus — list NVIDIA GPUs
+best-driver — print which NVIDIA driver best fits this system
+autoinstall — automatically install the best NVIDIA driver for this system
+help — print this help
+
+Example:
+$0 autoinstall
+(run from root)
+"
+}
+
 # shellcheck disable=SC2120
 _mktemp(){
 	mktemp --tmpdir="$KROKO_TMPDIR" "$@"
@@ -320,7 +334,7 @@ _cli_autoinstall(){
 }
 
 _main(){
-	case "$1" in
+	case "${1:-}" in
 		"get-gpus" )
 			_cli_get_gpus
 		;;
@@ -330,6 +344,14 @@ _main(){
 		"autoinstall" )
 			_cli_autoinstall
 		;;
+		"help" | "--help" | "-h" )
+			_echo_help
+			return 0
+		;;
+		* )
+			_echo_help
+			return 1
+		;;
 	esac
 }