Add CMDsubmitchange to gerrit_client

Grant the power to gerrit_client cmd to submit a change. Once
we create a change and update it via CMDchangeedit, we can
submit it if the service account has permission.

BUG=1207955
TEST=e2e

Change-Id: Ia3102641ffe5bb72f8f63ad80bf15b5478cf5a2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3039331
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Michael Moss <mmoss@chromium.org>
Commit-Queue: Xinan Lin <linxinan@chromium.org>

gerrit_client.py

@@ -237,6 +237,23 @@ def CMDpublishchangeedit(parser, args):
   write_result(result, opt)
 
 
+@subcommand.usage('[args ...]')
+def CMDsubmitchange(parser, args):
+  """Submit a Gerrit change."""
+  parser.add_option('-c', '--change', type=int, help='change number')
+  parser.add_option('--wait-for-merge',
+                    action="store_true",
+                    default=False,
+                    help='whether to wait for the merge')
+
+  (opt, args) = parser.parse_args(args)
+  result = gerrit_util.SubmitChange(urlparse.urlparse(opt.host).netloc,
+                                    opt.change,
+                                    wait_for_merge=opt.wait_for_merge)
+  logging.info(result)
+  write_result(result, opt)
+
+
 @subcommand.usage('')
 def CMDabandon(parser, args):
   """Abandons a Gerrit change."""