add osmo-bsc --vty-ref-xml: dump VTY ref XML to stdout

Add only a long option to not clutter the cmdline namespace.

To add a long option without a short letter is slightly complex: use the 'flag'
and 'val' mechanism as in 'man 3 getopt' to write an option index to
long_option.

Depends: Ic74bbdb6dc5ea05f03c791cc70184861e39cd492 (libosmocore)
Change-Id: I316efedb2c1652791434ecf14a1e261367cd2fb7

src/osmo-bsc/osmo_bsc_main.c

@@ -104,12 +104,14 @@ static void print_help()
 	printf("  -e --log-level number		Set a global loglevel.\n");
 	printf("  -r --rf-ctl NAME		A unix domain socket to listen for cmds.\n");
 	printf("  -t --testmode			A special mode to provoke failures at the MSC.\n");
+	printf("  --vty-ref-xml			Generate the VTY reference XML output and exit.\n");
 }
 
 static void handle_options(int argc, char **argv)
 {
 	while (1) {
 		int option_index = 0, c;
+		static int long_option = 0;
 		static struct option long_options[] = {
 			{"help", 0, 0, 'h'},
 			{"debug", 1, 0, 'd'},
@@ -122,6 +124,7 @@ static void handle_options(int argc, char **argv)
 			{"log-level", 1, 0, 'e'},
 			{"rf-ctl", 1, 0, 'r'},
 			{"testmode", 0, 0, 't'},
+			{"vty-ref-xml", 0, &long_option, 1},
 			{0, 0, 0, 0}
 		};
 
@@ -135,6 +138,15 @@ static void handle_options(int argc, char **argv)
 			print_usage();
 			print_help();
 			exit(0);
+		case 0:
+			switch (long_option) {
+			case 1:
+				vty_dump_xml_ref(stdout);
+				exit(0);
+			default:
+				fprintf(stderr, "error parsing cmdline options\n");
+				exit(2);
+			}
 		case 's':
 			log_set_use_color(osmo_stderr_target, 0);
 			break;