Add version and options to check for it

.gitignore

@@ -0,0 +1 @@
+build

src/addtax.c

@@ -3,10 +3,12 @@
 #include <libintl.h>
 #include <locale.h>
 #include <stdbool.h>
+#include <getopt.h>
 #include "misc.h"
 
 #define _(STRING) gettext(STRING)
 #define TAX 1.111111111
+#define VERSION "1.0.0"
 
 GtkLabel *calculated_value = NULL;
 
@@ -27,25 +29,34 @@ void calculate_tax(GtkWidget *entry) {
 
 int main(int argc, char *argv[]) {
 	int opt;
-	
 	float money;
+	int long_index = 0;
+	static struct option long_options[] = {
+		{"version",		no_argument,	0,	'v'},
+		{0,				0,				0,	0}
+	};
 	
 	setlocale(LC_ALL, "");
 	bindtextdomain("addtax", "/usr/share/locale/");
 	textdomain("addtax");
 	
 	if (argc > 1) {
-		while ((opt = getopt(argc, argv, "")) != -1) {
+		// Process options
+		while ((opt = getopt_long(argc, argv,"v", long_options, &long_index)) != -1) {
 			switch (opt) {
+				case 'v':
+					printf("%s %s\n", argv[0], VERSION);
+					break;
 				default:
 					fprintf(stderr, _("Usage: %s [prices...]\n"), argv[0]);
 					return 1;
 			}
 		}
 		
-		for (opt = 1; opt < argc; opt++) {
-			money = atof(argv[opt]);
-			if (is_float(argv[opt], money)) {
+		// Process arguments that are not options
+		while (optind < argc) {
+			money = atof(argv[optind]);
+			if (is_float(argv[optind++], money)) {
 				printf("$%d * %f = ", (int) round(money), TAX);
 				money = money * TAX;
 				printf("$%d\n", (int) round(money));