Fix various stray bugs in the GN auto-roller, and repair the DEPS file.

tools/gn/bin/roll_gn.py

 # Copyright 2014 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.
 
 """An auto-roller for GN binaries into Chromium.
 
 This script is used to update the GN binaries that a Chromium
 checkout uses. In order to update the binaries, one must follow
 four steps in order:
 
@@ skipping 284 matching lines @@
         print("buildtools git cl land failed: %d" % ret)
         if out:
             print(out)
         if err:
             print(err)
         return ret
 
     # Fetch the revision we just committed so that RollDEPS will find it.
     self.Call('git fetch', cwd=self.buildtools_dir)
 
+    # Reset buildtools to the new commit so that we're not still on the
+    # merged branch.
+    self.Call('git checkout origin/master', cwd=self.buildtools_dir)
+
     return 0
 
   def RollDEPS(self):
     ret, _, _ = self.Call('git new-branch roll_gn_%s' % self.new_gn_version)
     if ret:
       print('Failed to create a new branch for roll_gn_%s' %
             self.new_gn_version)
       return 1
 
     _, out, _ = self.Call('git rev-parse origin/master',
                           cwd=self.buildtools_dir)
     new_buildtools_commitish = out.strip()
 
     new_deps_lines = []
     old_buildtools_commitish = ''
     with open(os.path.join(self.chromium_src_dir, 'DEPS')) as fp:
       for l in fp.readlines():
         m = re.match(".*'buildtools_revision':.*'(.+)',", l)
         if m:
           old_buildtools_commitish = m.group(1)
-          new_deps_lines.append("  'buildtools_revision': '%s'," %
+          new_deps_lines.append("  'buildtools_revision': '%s',\n" %
                                 new_buildtools_commitish)
         else:
           new_deps_lines.append(l)
 
     if not old_buildtools_commitish:
       print('Could not update DEPS properly, exiting')
       return 1
 
     with open('DEPS', 'w') as fp:
       fp.write(''.join(new_deps_lines) + '\n')
 
     desc = self.GetDEPSRollDesc(old_buildtools_commitish,
                                 new_buildtools_commitish)
     desc_file = tempfile.NamedTemporaryFile(delete=False)
     try:
       desc_file.write(desc)
       desc_file.close()
       self.Call('git commit -a -F %s' % desc_file.name)
       self.Call('git-cl upload -f --send-mail --use-commit-queue')
     finally:
       os.remove(desc_file.name)
+
+    # Intentionally leave the src checkout on the new branch with the roll
+    # since we're not auto-committing it.
+
     return 0
 
   def GetBuildtoolsDesc(self):
     gn_changes = self.GetGNChanges()
     return (
       'Roll gn %s..%s (r%s:r%s)\n'
       '\n'
       '%s'
       '\n'
       'TBR=%s\n' % (
@@ skipping 40 matching lines @@
   def Call(self, cmd, cwd=None):
     proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, shell=True,
                             cwd=(cwd or self.chromium_src_dir))
     out, err = proc.communicate()
     return proc.returncode, out, err
 
 
 if __name__ == '__main__':
   roller = GNRoller()
   sys.exit(roller.Roll())