Add a --markdown flag to GN to be able to output help in markdown.

tools/gn/switches.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "tools/gn/switches.h"
 
 namespace switches {
 
 const char kArgs[] = "args";
 const char kArgs_HelpShort[] =
@@ skipping 51 matching lines @@
 const char kDotfile_Help[] =
     "--dotfile: override the name of the \".gn\" file.\n"
     "\n"
     "  Normally GN loads the \".gn\"file  from the source root for some basic\n"
     "  configuration (see \"gn help dotfile\"). This flag allows you to\n"
     "  use a different file.\n"
     "\n"
     "  Note that this interacts with \"--root\" in a possibly incorrect way.\n"
     "  It would be nice to test the edge cases and document or fix.\n";
 
+const char kMarkdown[] = "markdown";
+const char kMarkdown_HelpShort[] =
+    "--markdown: write the output in the Markdown format.";
+const char kMarkdown_Help[] =
+    "--markdown: write the output in the Markdown format.\n";
+
 const char kNoColor[] = "nocolor";
 const char kNoColor_HelpShort[] =
     "--nocolor: Force non-colored output.";
 const char kNoColor_Help[] = COLOR_HELP_LONG;
 
 const char kQuiet[] = "q";
 const char kQuiet_HelpShort[] =
     "-q: Quiet mode. Don't print output on success.";
 const char kQuiet_Help[] =
     "-q: Quiet mode. Don't print output on success.\n"
@@ skipping 95 matching lines @@
 
 #define INSERT_VARIABLE(var) \
     info_map[k##var] = SwitchInfo(k##var##_HelpShort, k##var##_Help);
 
 const SwitchInfoMap& GetSwitches() {
   static SwitchInfoMap info_map;
   if (info_map.empty()) {
     INSERT_VARIABLE(Args)
     INSERT_VARIABLE(Color)
     INSERT_VARIABLE(Dotfile)
+    INSERT_VARIABLE(Markdown)
     INSERT_VARIABLE(NoColor)
     INSERT_VARIABLE(Root)
     INSERT_VARIABLE(Quiet)
     INSERT_VARIABLE(Time)
     INSERT_VARIABLE(Tracelog)
     INSERT_VARIABLE(Verbose)
     INSERT_VARIABLE(Version)
   }
   return info_map;
 }
 
 #undef INSERT_VARIABLE
 
 }  // namespace switches