Add a target in GN that generates a last_change.h file for the SVN revision.

tools/gn/gn_main.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 "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/strings/utf_string_conversions.h"
 #include "tools/gn/commands.h"
 #include "tools/gn/err.h"
 #include "tools/gn/location.h"
+#include "tools/gn/standard_out.h"
+
+// Only the GN-generated build makes this header for now.

[viettrungluu, 2013/11/06 18:39:22]

Is this a TODO?

+#if defined(GN_BUILD)
+#include "build/util/last_change.h"
+#else
+#define LAST_CHANGE "UNKNOWN"
+#endif
 
 namespace {
 
 std::vector<std::string> GetArgs(const CommandLine& cmdline) {
   CommandLine::StringVector in_args = cmdline.GetArgs();
 #if defined(OS_WIN)
   std::vector<std::string> out_args;
   for (size_t i = 0; i < in_args.size(); i++)
     out_args.push_back(base::WideToUTF8(in_args[i]));
   return out_args;
@@ skipping 11 matching lines @@
 #endif
   CommandLine::Init(argc, argv);
 
   const CommandLine& cmdline = *CommandLine::ForCurrentProcess();
   std::vector<std::string> args = GetArgs(cmdline);
 
   std::string command;
   if (cmdline.HasSwitch("help")) {
     // Make "--help" default to help command.
     command = commands::kHelp;
+  } else if (cmdline.HasSwitch("version")) {
+    // Make "--version" print the version and exit.
+    OutputString(std::string(LAST_CHANGE) + "\n");
+    exit(0);
   } else if (args.empty()) {
     command = commands::kGen;
   } else {
     command = args[0];
     args.erase(args.begin());
   }
 
   const commands::CommandInfoMap& command_map = commands::GetCommands();
   commands::CommandInfoMap::const_iterator found_command =
       command_map.find(command);
 
   int retval;
   if (found_command != command_map.end()) {
     retval = found_command->second.runner(args);
   } else {
     Err(Location(),
         "Command \"" + command + "\" unknown.").PrintToStdout();
     commands::RunHelp(std::vector<std::string>());
     retval = 1;
   }
 
   exit(retval);  // Don't free memory, it can be really slow!
   return retval;
 }