message: Add `search --graph` option
  This functionality should eventually be moved elsewhere
diff: namespace vcpkg::Commands::Search
  {
  + static const std::string OPTION_GRAPH = "--graph"; //TODO: This should find a better home, eventually
  +
  + static std::string replace_dashes_with_underscore(const std::string& input)
  + {
  + std::string output = input;
  + std::replace(output.begin(), output.end(), '-', '_');
  + return output;
  + }
  +
  + static std::string create_graph_as_string(const std::vector<SourceParagraph>& source_paragraphs)
  + {
  + int empty_node_count = 0;
  +
  + std::string s;
  + s.append("digraph G{ rankdir=LR; edge [minlen=3]; overlap=false;");
  +
  + for (const SourceParagraph& source_paragraph : source_paragraphs)
  + {
  + if (source_paragraph.depends.empty())
  + {
  + empty_node_count++;
  + continue;
  + }
  +
  + const std::string name = replace_dashes_with_underscore(source_paragraph.name);
  + s.append(Strings::format("%s;", name));
  + for (const dependency& d : source_paragraph.depends)
  + {
  + const std::string dependency_name = replace_dashes_with_underscore(d.name);
  + s.append(Strings::format("%s -> %s;", name, dependency_name));
  + }
  + }
  +
  + s.append(Strings::format("empty [label=\"%d singletons...\"]; }", empty_node_count));
  + return s;
  + }
  +
  static std::vector<SourceParagraph> read_all_source_paragraphs(const vcpkg_paths& paths)
  {
  std::vector<SourceParagraph> output;
  @@ -25,9 +62,7 @@ namespace vcpkg::Commands::Search
  auto srcpgh = SourceParagraph(pghs[0]);
  output.push_back(srcpgh);
  }
  - catch (std::runtime_error const&)
  - {
  - }
  + catch (std::runtime_error const&) { }
  }
  return output;
  @@ -46,9 +81,15 @@ namespace vcpkg::Commands::Search
  static const std::string example = Strings::format("The argument should be a substring to search for, or no argument to display all libraries.\n%s",
  Commands::Help::create_example_string("search png"));
  args.check_max_arg_count(1, example);
  - args.check_and_get_optional_command_arguments({});
  + const std::unordered_set<std::string> options = args.check_and_get_optional_command_arguments({ OPTION_GRAPH });
  const std::vector<SourceParagraph> source_paragraphs = read_all_source_paragraphs(paths);
  + if (options.find(OPTION_GRAPH) != options.cend())
  + {
  + const std::string graph_as_string = create_graph_as_string(source_paragraphs);
  + System::println(graph_as_string);
  + exit(EXIT_SUCCESS);
  + }
  if (args.command_arguments.size() == 0)
  {
  