Revert making apply_issue assume 'master'

checkout.py

 # coding=utf8
 # Copyright (c) 2012 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.
 """Manages a project checkout.
 
 Includes support for svn, git-svn and git.
 """
 
 import ConfigParser
@@ skipping 544 matching lines @@
 
 class GitCheckout(CheckoutBase):
   """Manages a git checkout."""
   def __init__(self, root_dir, project_name, remote_branch, git_url,
       commit_user, post_processors=None, base_ref=None):
     super(GitCheckout, self).__init__(root_dir, project_name, post_processors)
     self.base_ref = base_ref
     self.git_url = git_url
     self.commit_user = commit_user
     self.remote_branch = remote_branch
-    assert self.remote_branch
     # The working branch where patches will be applied. It will track the
     # remote branch.
     self.working_branch = 'working_branch'
     # There is no reason to not hardcode origin.
     self.pull_remote = 'origin'
     self.push_remote = 'upstream'
 
   def prepare(self, revision):
     """Resets the git repository in a clean state.
 
@@ skipping 42 matching lines @@
 
     Also commits the changes on the local branch.
 
     Ignores svn properties and raise an exception on unexpected ones.
     """
     post_processors = post_processors or self.post_processors or []
     # It this throws, the checkout is corrupted. Maybe worth deleting it and
     # trying again?
     if self.remote_branch:
       self._check_call_git(
-          ['checkout', 
-           '-b', self.working_branch, 
+          ['checkout', '-b', self.working_branch,
            '-t', '%s/%s' % (self.pull_remote, self.remote_branch),
            '--quiet'])
 
     for index, p in enumerate(patches):
       stdout = []
       try:
         filepath = os.path.join(self.project_path, p.filename)
         if p.is_delete:
           if (not os.path.exists(filepath) and
               any(p1.source_filename == p.filename for p1 in patches[0:index])):
@@ skipping 182 matching lines @@
   def revisions(self, rev1, rev2):
     return self.checkout.revisions(rev1, rev2)
 
   @property
   def project_name(self):
     return self.checkout.project_name
 
   @property
   def project_path(self):
     return self.checkout.project_path