message: [vcpkg-help] Improve help, including a list of topics.
diff: namespace vcpkg::Commands::Help
  {
  + void help_topics()
  + {
  + System::println("Available help topics:\n"
  + " triplet\n"
  + " integrate\n"
  + " export");
  + }
  +
  void help_topic_valid_triplet(const VcpkgPaths& paths)
  {
  System::println("Available architecture triplets:");
  @@ -14,6 +22,21 @@ namespace vcpkg::Commands::Help
  }
  }
  + void help_topic_export()
  + {
  + System::println("Summary:\n"
  + " vcpkg export [options] <pkgs>...\n"
  + "\n"
  + "Options:\n"
  + " --7zip Export to a 7zip (.7z) file\n"
  + " --dry-run Do not actually export\n"
  + " --nuget Export a NuGet package\n"
  + " --nuget-id=<id> Specify the id for the exported NuGet package\n"
  + " --nuget-version=<ver> Specify the version for the exported NuGet package\n"
  + " --raw Export to an uncompressed directory\n"
  + " --zip Export to a zip file");
  + }
  +
  void print_usage()
  {
  System::println(
  @@ -25,6 +48,8 @@ namespace vcpkg::Commands::Help
  " vcpkg list List installed packages\n"
  " vcpkg update Display list of packages for updating\n"
  " vcpkg hash <file> [alg] Hash a file by specific algorithm, default SHA512\n"
  + " vcpkg help topics Display the list of help topics\n"
  + " vcpkg help <topic> Display help for a specific topic\n"
  "\n"
  "%s" // Integration help
  "\n"
  @@ -77,14 +102,28 @@ namespace vcpkg::Commands::Help
  Checks::exit_success(VCPKG_LINE_INFO);
  }
  const auto& topic = args.command_arguments[0];
  - if (topic == "triplet")
  + if (topic == "triplet" || topic == "triplets" || topic == "triple")
  {
  help_topic_valid_triplet(paths);
  }
  + else if (topic == "export")
  + {
  + help_topic_export();
  + }
  + else if (topic == "integrate")
  + {
  + System::print("Commands:\n"
  + "%s",
  + Integrate::INTEGRATE_COMMAND_HELPSTRING);
  + }
  + else if (topic == "topics")
  + {
  + help_topics();
  + }
  else
  {
  System::println(System::Color::error, "Error: unknown topic %s", topic);
  - print_usage();
  + help_topics();
  Checks::exit_fail(VCPKG_LINE_INFO);
  }
  Checks::exit_success(VCPKG_LINE_INFO);
  