Online documentation for single-letter options.

It's mostly worked out, but there's a few odd corner cases,
especially around the auto-gen of negation options.  It also
got me to start thinking about "is a required negatable option
still required of its negation?"  Similar questions revolve
around requiring such options.

I'm punting on these for now, but I think it makes sense to
perhaps make those incompatible with such domains.  Or to treat
the two options as a shared-fate unit.  But is `-O -o -O -o` a
violation of exclusivity?  If we wind up returning to the default
state, have we actually passed that option, with respect to
"requirement"?  I have to think about that some more.

A commit message isn't the best place to capture this, but I
didn't want to lose this thought.

ProgramOptions.cc

@@ -46,6 +46,8 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 		std::map< std::type_index, std::set< const DomainBase * > > domains;
 
 		ArgumentStance argumentStance;
+
+		std::set< char > shortAliases;
 	};
 
 	namespace
@@ -62,6 +64,8 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 
 		struct ExclusivityEntry
 		{
+			// This gets used during the parsing process to indicate which previous entry from this domain
+			// has been seen, if any.
 			std::optional< std::string > previous;
 		};
 
@@ -157,6 +161,20 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 			incompatibles.erase( name );
 			if( incompatibles.empty() ) return;
 
+			std::set< std::string > incompatibleAliases;
+			for( const auto &incompat: incompatibles )
+			{
+				const auto &aliases= programOptions().at( incompat ).shortAliases;
+				for( const auto alias: aliases )
+				{
+					incompatibleAliases.insert( "-"s + alias );
+				}
+			}
+			for( const auto &alias: incompatibleAliases )
+			{
+				incompatibles.insert( alias );
+			}
+
 			out << "\nIncompatible with: \n\n";
 			bool first= true;
 			for( const auto &incompat: incompatibles )
@@ -168,6 +186,19 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 			out << std::endl;
 		}
 
+		void
+		aliasHelpText( std::ostream &out, const std::string &name )
+		{
+			const auto &aliases= programOptions().at( name ).shortAliases;
+
+			if( aliases.empty() ) return;
+
+			for( const auto &alias: aliases )
+			{
+				out << "-" << alias << ":" << std::endl;
+			}
+		}
+
 		void
 		printAllOptionsHelp( const std::optional< std::string > canonicalProgramName )
 		{
@@ -200,9 +231,10 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 			{
 				// When turning off wrapping, here, we also emit a newline between entries.
 				AutoRAII endline{ []{}, []{ std::cout << std::endl; } };
+				aliasHelpText( std::cout, name );
 				auto wrapping= adaptStream( StartWrap{ width, alignmentWidth }, std::cout );
 
-				const auto &[ _, helpText, defaultBuilder, domains, argumentStance ]= def;
+				const auto &[ _, helpText, defaultBuilder, domains, argumentStance, aliases ]= def;
 
 				VariableMap substitutions=
 				{
@@ -244,6 +276,7 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 				}
 
 				std::cout << std::endl;
+				std::cout << EndWrap;
 			}
 		}
 	}
@@ -307,7 +340,8 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 					throw std::logic_error{ "Short form alias mapping of `-"s + key + "` for option `--"
 							+ name + "` is invalid, because the long name doesn't exist." };
 				}
-				const auto &[ _, help, builder, domains, stance ]= programOptions().at( "--" + name );
+
+				const auto &stance= programOptions().at( "--" + name ).argumentStance;
 				if( stance == ArgumentStance::Required )
 				{
 					throw std::logic_error{ "Short form alias mapping of `-"s + key + "` for option `--"
@@ -322,7 +356,21 @@ namespace Alepha::Hydrogen  ::detail::  ProgramOptions_m
 		{
 			validateShortAliases( shortAliases );
 
-			// TODO: Incorporate short aliases into the help...
+			for( const auto &[ alias, option ]: shortAliases )
+			{
+				programOptions().at( "--"s + option ).shortAliases.insert( alias );
+
+				const auto &domainMap= programOptions().at( "--"s + option ).domains;
+				for( const auto &[ requirement, domains ]: domainMap )
+				{
+					if( requirement != typeid( RequirementDomain ) ) continue;
+
+					for( const auto &domain: domains )
+					{
+						requiredOptions()[ domain ].push_back( "-"s + alias );
+					}
+				}
+			}
 		}
 
 		std::vector< std::string >