--- a/helpers/build-date.c	Sun Jan 27 22:20:26 2019 +0000
+++ b/helpers/build-date.c	Sun Jan 27 22:35:04 2019 +0000
@@ -5,6 +5,8 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <strings.h>
 #include <time.h>
 
 main(argc, argv)
@@ -13,18 +15,21 @@
 	time_t now;
 	struct tm *tm;
 
-	if (argc < 2 || argc > 3) {
-		fprintf(stderr, "usage: %s config_name [target_name]\n",
+	if (argc < 2 || argc > 4) {
+		fprintf(stderr,
+			"usage: %s config_name target_name src_version\n",
 			argv[0]);
 		exit(1);
 	}
 	time(&now);
 	tm = gmtime(&now);
 	printf("const char firmware_version_str[] =\n");
-	if (argv[2])
+	if (argc >= 3)
 		printf("\"FreeCalypso Magnetite %s (%s), ", argv[1], argv[2]);
 	else
 		printf("\"FreeCalypso Magnetite %s, ", argv[1]);
+	if (argc >= 4 && strcmp(argv[3], "unknown"))
+		printf("source version %s, ", argv[3]);
 	printf("build date %d-%02d-%02dT%02d:%02d:%02dZ\";\n",
 		tm->tm_year+1900, tm->tm_mon+1, tm->tm_mday,
 		tm->tm_hour, tm->tm_min, tm->tm_sec);