[Docker] Added a check to make sure an argument is passed (OpenAPIToo…

…ls#6207)

* added a check to make sure an argument is passed

* list available commands

docker-entrypoint.sh

@@ -12,7 +12,16 @@ codegen="${cli}/target/openapi-generator-cli.jar"
 # We code in a list of commands here as source processing is potentially buggy (requires undocumented conventional use of annotations).
 # A list of known commands helps us determine if we should compile CLI. There's an edge-case where a new command not added to this
 # list won't be considered a "real" command. We can get around that a bit by checking CLI completions beforehand if it exists.
-commands="list,generate,meta,help,config-help,validate,version"
+commands="config-help,generate,help,list,meta,validate,version"
+
+if [ $# == 0 ]; then
+	echo "No command specified. Available commands:"
+	for i in $(echo $commands | sed "s/,/ /g")
+	do
+		echo "  $i"
+	done
+	exit
+fi
 
 # if CLI jar exists, check $1 against completions available in the CLI
 if [[ -f "${codegen}" && -n "$(java ${JAVA_OPTS} -jar "${codegen}" completion | grep "^$1\$" )" ]]; then