Fix Issue nanocurrency#3748

Sorted command line options output

nano/lib/utility.cpp

@@ -2,6 +2,7 @@
 
 #include <boost/dll/runtime_symbol_info.hpp>
 #include <boost/filesystem.hpp>
+#include <boost/program_options.hpp>
 
 #include <cstddef>
 #include <iostream>
@@ -196,3 +197,23 @@ void assert_internal (char const * check_expr, char const * func, char const * f
 
 	abort ();
 }
+
+// Issue #3748
+void nano::sort_options_description (const boost::program_options::options_description & source, boost::program_options::options_description & target)
+{
+	// Grab all of the options, get the option display name, stick it in a map using the display name as
+	// the key (the map will sort) and the value as the option itself.
+	const auto & options = source.options ();
+	std::map<std::string, boost::shared_ptr<boost::program_options::option_description>> sorted_options;
+	for (const auto & option : options)
+	{
+		auto pair = std::make_pair (option->canonical_display_name (2), option);
+		sorted_options.insert (pair);
+	}
+
+	// Rebuild for display purposes only.
+	for (const auto & option_pair : sorted_options)
+	{
+		target.add (option_pair.second);
+	}
+}

nano/lib/utility.hpp

@@ -22,6 +22,11 @@ namespace system
 {
 	class error_code;
 }
+
+namespace program_options
+{
+	class options_description;
+}
 }
 
 void assert_internal (char const * check_expr, char const * func, char const * file, unsigned int line, bool is_release_assert, std::string_view error = "");
@@ -203,4 +208,7 @@ constexpr TARGET_TYPE narrow_cast (SOURCE_TYPE const & val)
 	debug_assert (val == static_cast<SOURCE_TYPE> (res));
 	return res;
 }
+
+// Issue #3748
+void sort_options_description (const boost::program_options::options_description & source, boost::program_options::options_description & target);
 }

nano/nano_node/entry.cpp

@@ -2033,7 +2033,11 @@ int main (int argc, char * const * argv)
 		}
 		else
 		{
-			std::cout << description << std::endl;
+			// Issue #3748
+			// Regardless how the options were added, output the options in alphabetical order so they are easy to find.
+			boost::program_options::options_description sorted_description ("Command line options");
+			nano::sort_options_description (description, sorted_description);
+			std::cout << sorted_description << std::endl;
 			result = -1;
 		}
 	}

nano/nano_rpc/entry.cpp

@@ -156,7 +156,11 @@ int main (int argc, char * const * argv)
 	}
 	else
 	{
-		std::cout << description << std::endl;
+		// Issue #3748
+		// Regardless how the options were added, output the options in alphabetical order so they are easy to find.
+		boost::program_options::options_description sorted_description ("Command line options");
+		nano::sort_options_description (description, sorted_description);
+		std::cout << sorted_description << std::endl;
 	}
 
 	return 1;