gclient: handle case for upstream has rebased

gclient_scm.py

 # Copyright (c) 2009 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.
 
 """Gclient-specific SCM-specific operations."""
 
 import logging
 import os
 import re
 import subprocess
@@ skipping 117 matching lines @@
 
     if not os.path.exists(self.checkout_path):
       self._Run(['clone', url, self.checkout_path],
                 cwd=self._root_dir, redirect_stdout=False)
       if revision:
         self._Run(['reset', '--hard', revision], redirect_stdout=False)
       files = self._Run(['ls-files']).split()
       file_list.extend([os.path.join(self.checkout_path, f) for f in files])
       return
 
-    self._Run(['remote', 'update'], redirect_stdout=False)
     new_base = 'origin'
     if revision:
       new_base = revision
+    cur_branch = self._Run(['symbolic-ref', 'HEAD']).split('/')[-1]
+    merge_base = self._Run(['merge-base', 'HEAD', new_base])
+    self._Run(['remote', 'update'], redirect_stdout=False)
     files = self._Run(['diff', new_base, '--name-only']).split()
     file_list.extend([os.path.join(self.checkout_path, f) for f in files])
-    self._Run(['rebase', '-v', new_base], redirect_stdout=False)
+    self._Run(['rebase', '-v', '--onto', new_base, merge_base, cur_branch],
+                redirect_stdout=False)
     print "Checked out revision %s." % self.revinfo(options, (), None)
 
   def revert(self, options, args, file_list):
     """Reverts local modifications.
 
     All reverted files will be appended to file_list.
     """
     __pychecker__ = 'unusednames=args'
     path = os.path.join(self._root_dir, self.relpath)
     if not os.path.isdir(path):
@@ skipping 300 matching lines @@
           self.ReplaceAndPrint(line)
         else:
           if (line.startswith(self.original_prefix) or
               line.startswith(self.working_prefix)):
             self.ReplaceAndPrint(line)
           else:
             print line
 
     filterer = DiffFilterer(self.relpath)
     self.RunAndFilterOutput(command, path, False, False, filterer.Filter)