Use git_cl.Changelist.GetUpstreamBranch() for diff in submit_try

tools/submit_try

 #!/usr/bin/python
 
 # 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.
 
 
 """
 submit_try: Submit a try request.
 
@@ skipping 19 matching lines @@
 ALL_BUILDERS = 'all'
 # Alias which can be used to run a try on all compile builders.
 COMPILE_BUILDERS = 'compile'
 # Alias which can be used to run a try on all builders that are run in the CQ.
 CQ_BUILDERS = 'cq'
 # Alias which can be used to specify a regex to choose builders.
 REGEX = 'regex'
 
 ALL_ALIASES = [ALL_BUILDERS, COMPILE_BUILDERS, CQ_BUILDERS, REGEX]
 
+GIT = 'git.bat' if os.name == 'nt' else 'git'
+
 # Contact information for the build master.
 SKIA_BUILD_MASTER_HOST = str(buildbot_globals.Get('public_master_host'))
 SKIA_BUILD_MASTER_PORT = str(buildbot_globals.Get('public_external_port'))
 
 # All try builders have this suffix.
 TRYBOT_SUFFIX = '-Trybot'
 
 # String for matching the svn url of the try server inside codereview.settings.
 TRYSERVER_SVN_URL = 'TRYSERVER_SVN_URL: '
 
@@ skipping 210 matching lines @@
     if args.revision:
       try_args.extend(['-r', args.revision])
     print ' '.join(try_args)
     proc = subprocess.Popen(try_args, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT)
     if proc.wait() != 0:
       raise Exception('Failed to submit try request: %s' % (
           proc.communicate()[0]))
     print proc.communicate()[0]
   else:
-    # Create the diff file.
-    cmd = ['git.bat' if os.name == 'nt' else 'git', 'diff', 'origin/master']
+    # Find depot_tools. This is needed to import git_cl and trychange.
+    sys.path.append(FindDepotTools())
+    import git_cl
+    import trychange
+
+    cmd = [GIT, 'diff', git_cl.Changelist().GetUpstreamBranch(),
+           '--no-ext-diff']
     proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     if proc.wait() != 0:
       raise Exception('Failed to capture git diff!')
 
     temp_dir = tempfile.mkdtemp()
     try:
       diff_file = os.path.join(temp_dir, 'patch.diff')
       with open(diff_file, 'wb') as f:
         f.write(proc.communicate()[0])
   
-      # Find depot_tools. This is needed to import trychange.
-      sys.path.append(FindDepotTools())
-      import trychange
       try_args = ['--use_svn',
                   '--svn_repo', GetTryRepo(),
                   '--root', GetCheckoutRoot(is_svn),
                   '--bot', botlist,
                   '--diff', diff_file,
                   ]
       if args.revision:
         try_args.extend(['-r', args.revision])
 
       # Submit the try request.
@@ skipping 11 matching lines @@
 
   # Parse and validate the command-line arguments.
   args = ValidateArgs(sys.argv[1:], trybots=trybots, is_svn=is_svn)
 
   # Submit the try request.
   SubmitTryRequest(args, is_svn=is_svn)
 
 
 if __name__ == '__main__':
   sys.exit(main())