Subcommand plurality (#1169)

Partially address #1168 fix subcommand plurality when subcommand_max count is 0

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

fuzz/cli11_app_fuzz.cpp

@@ -29,6 +29,8 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
     try {
         if(pstring_start > 0) {
             app->parse(parseString.substr(pstring_start));
+            // test to make sure no seg fault or other errors occur
+            std::ignore = app->help("", CLI::AppFormatMode::All);
         } else {
             app->parse(parseString);
         }
@@ -39,7 +41,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
         // this just indicates we caught an error known by CLI
         return 0;  // Non-zero return values are reserved for future use.
     }
-    if(fuzzdata.support_config_file_only()) {
+    if(fuzzdata.supports_config_file()) {
         CLI::FuzzApp fuzzdata2;
         auto app2 = fuzzdata2.generateApp();
         // should be able to write the config to a file and read from it again

fuzz/fuzzApp.cpp

@@ -555,6 +555,16 @@ std::size_t FuzzApp::add_custom_options(CLI::App *app, const std::string &descri
                 }
             }
             current_index = end_option + 9;
+        } else if(description_string.compare(current_index, 11, "<subcommand") == 0) {
+            auto end_sub_label = description_string.find_first_of('>', current_index + 12);
+            if(end_sub_label == std::string::npos) {
+                break;
+            }
+            auto end_sub = description_string.find("</subcommand>", end_sub_label + 1);
+            if(end_sub == std::string::npos) {
+                break;
+            }
+
         } else {
             if(isspace(description_string[current_index]) != 0) {
                 ++current_index;

fuzz/fuzzApp.hpp

@@ -63,7 +63,7 @@ class FuzzApp {
     /** modify an option based on string*/
     static void modify_option(CLI::Option *opt, const std::string &modifier);
 
-    CLI11_NODISCARD bool support_config_file_only() const { return !non_config_required; }
+    CLI11_NODISCARD bool supports_config_file() const { return !non_config_required; }
     int32_t val32{0};
     int16_t val16{0};
     int8_t val8{0};