Fix git depot_tools update flow.

update_depot_tools.bat

Index: update_depot_tools.bat
diff --git a/update_depot_tools.bat b/update_depot_tools.bat
new file mode 100644
index 0000000000000000000000000000000000000000..40c041f83910ff938848930fbac7e75b87714614
--- /dev/null
+++ b/update_depot_tools.bat
@@ -0,0 +1,37 @@
+@echo off
+:: Copyright (c) 2010 The Chromium Authors. All rights reserved.

[M-A Ruel, 2012/03/21 01:57:09]

2012

+:: Use of this source code is governed by a BSD-style license that can be
+:: found in the LICENSE file.
+
+:: This batch file will try to sync the root directory.
+
+:: This is required with cygwin only.

[M-A Ruel, 2012/03/21 01:57:09]

Actually, cygwin should not get there. :/

[gab, 2012/03/21 13:31:46]

This is coming straight from the old script. I think it's to make sure our
version of git/svn has priority over the cygwin one, by putting %~dp0 at the
start of the path.

[M-A Ruel, 2012/03/21 14:32:50]

Yeah and that's wrong. Remove lines 8 and 10. 

[gab, 2012/03/21 14:37:52]

Ok, done.

+setlocal
+PATH=%~dp0;%PATH%
+
+:: Will download svn and python.
+:: If you don't want to install the depot_tools version of these tools, remove
+:: the 'force' option on the next command. The tools will be installed only if
+:: not already in the PATH environment variable.
+call "%~dp0bootstrap\win\win_tools.bat" force
+if errorlevel 1 goto :EOF
+
+:: Shall skip automatic update?
+IF "%DEPOT_TOOLS_UPDATE%" == "0" GOTO :EOF
+
+:: We need either .\.svn\. or .\.git\. to be able to sync.
+IF EXIST "%~dp0.svn\." GOTO :SVN_UPDATE
+IF EXIST "%~dp0.git\." GOTO :GIT_UPDATE
+echo Error updating depot_tools, no revision tool found.
+goto :EOF
+
+
+:SVN_UPDATE
+call svn up -q "%~dp0"
+goto :EOF
+
+
+:GIT_UPDATE
+cd "%~dp0"
+call git svn rebase -q -q
+goto :EOF