Escape "--" in markdown rendering for GN reference docs.

tools/gn/standard_out.cc

 // Copyright (c) 2013 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/standard_out.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/logging.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
 #include "build/build_config.h"
 #include "tools/gn/switches.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #else
 #include <stdio.h>
 #include <unistd.h>
 #endif
 
@@ skipping 95 matching lines @@
         ::SetConsoleTextAttribute(hstdout,
                                   FOREGROUND_BLUE | FOREGROUND_INTENSITY);
         break;
       case DECORATION_YELLOW:
         ::SetConsoleTextAttribute(hstdout,
                                   FOREGROUND_RED | FOREGROUND_GREEN);
         break;
     }
   }
 
-  ::WriteFile(hstdout, output.c_str(), static_cast<DWORD>(output.size()),
+  std::string tmpstr = output;
+  if (is_markdown && dec == DECORATION_YELLOW) {
+    // https://code.google.com/p/gitiles/issues/detail?id=77
+    // Gitiles will replace "--" with an em dash in non-code text.
+    // Figuring out all instances of this might be difficult, but we can
+    // at least escape the instances where this shows up in a heading.
+    base::ReplaceSubstringsAfterOffset(&tmpstr, 0, "--", "\\--");
+  }
+  ::WriteFile(hstdout, tmpstr.c_str(), static_cast<DWORD>(tmpstr.size()),
               &written, nullptr);
 
   if (is_markdown) {
     OutputMarkdownDec(dec);
   } else if (is_console) {
     ::SetConsoleTextAttribute(hstdout, default_attributes);
   }
 }
 
 #else
@@ skipping 17 matching lines @@
         break;
       case DECORATION_BLUE:
         WriteToStdOut("\e[34m\e[1m");
         break;
       case DECORATION_YELLOW:
         WriteToStdOut("\e[33m\e[1m");
         break;
     }
   }
 
-  WriteToStdOut(output.data());
+  std::string tmpstr = output;
+  if (is_markdown && dec == DECORATION_YELLOW) {
+    // https://code.google.com/p/gitiles/issues/detail?id=77
+    // Gitiles will replace "--" with an em dash in non-code text.
+    // Figuring out all instances of this might be difficult, but we can
+    // at least escape the instances where this shows up in a heading.
+    base::ReplaceSubstringsAfterOffset(&tmpstr, 0, "--", "\\--");
+  }
+  WriteToStdOut(tmpstr.data());
 
   if (is_markdown) {
     OutputMarkdownDec(dec);
   } else if (is_console && dec != DECORATION_NONE) {
     WriteToStdOut("\e[0m");
   }
 }
 
 #endif
 
@@ skipping 80 matching lines @@
       }
     }
 
     OutputString(line + "\n", dec);
   }
 
   if (is_markdown && in_body)
     OutputString("\n```\n");
 }