add action for what to do

cmdline.ggo

@@ -27,3 +27,4 @@
 option "verbose" v "Print more information" flag off
 option "reader" r "Only use a matching reader" string optional
 option "key" k "Authentication key to use" string optional default="010203040506070801020304050607080102030405060708"
+option "action" a "Action to take" values="version" enum

yubico-piv-tool.c

@@ -318,7 +318,9 @@ int main(int argc, char *argv[]) {
     return EXIT_FAILURE;
   }
 
+  if(args_info.action_arg == action_arg_version) {
     print_version(&card, args_info.verbose_flag);
+  }
 
   return EXIT_SUCCESS;
 }