Multiple footer printing in help (#1161)

Fixes #1156 

For option groups removes inheritance of the footer and help option, so
those are not printed by default for option groups. It is still possible
to set them again on the option group.

---------

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

Author: phlptp

include/CLI/App.hpp

@@ -733,6 +733,9 @@ class App {
         auto *ptr = option_group.get();
         // move to App_p for overload resolution on older gcc versions
         App_p app_ptr = std::dynamic_pointer_cast<App>(option_group);
+        // don't inherit the footer in option groups and clear the help flag by default
+        app_ptr->footer_ = "";
+        app_ptr->set_help_flag();
         add_subcommand(std::move(app_ptr));
         return ptr;
     }

tests/HelpTest.cpp

@@ -85,6 +85,25 @@ TEST_CASE("THelp: FooterCallbackBoth", "[help]") {
     CHECK_THAT(help, Contains("foot!!!!"));
 }
 
+/// @brief from github issue #1156
+TEST_CASE("THelp: FooterOptionGroup", "[help]") {
+    CLI::App app{"My prog"};
+
+    app.footer("Report bugs to [email protected]");
+
+    app.add_option_group("group-a", "");
+
+    app.add_option_group("group-b", "");
+
+    std::string help = app.help();
+
+    auto footer_loc = help.find("[email protected]");
+    auto footer_loc2 = help.find("[email protected]", footer_loc + 10);
+    CHECK(footer_loc != std::string::npos);
+    // should only see the footer once
+    CHECK(footer_loc2 == std::string::npos);
+}
+
 TEST_CASE("THelp: OptionalPositional", "[help]") {
     CLI::App app{"My prog", "program"};