Fix help text

src/main.cpp

@@ -87,9 +87,15 @@ static void process(const char* path) {
 }
 
 static void print_help() {
-    std::cout << "usage: tagger [-h|--version]\n";
+    std::cout << "usage: tagger [-h|--version] [-l] [-s] [-a tag] [-d tag] [-c tag -i tag] file...\n";
     std::cout << "  -h, --help    show this help text and exit\n";
     std::cout << "  --version     show version number and exit\n";
+    std::cout << "  -l, --list    list all tags\n";
+    std::cout << "  -s, --sort    write tags sorted alphabetically\n";
+    std::cout << "  -a, --add     add a tag\n";
+    std::cout << "  -d, --delete  delete a tag\n";
+    std::cout << "  -c, --change  change a tag\n";
+    std::cout << "  -i, --into    into new value\n";
 }
 
 static void print_version() {