Support --target_branch=refs/meta/config branch

This simplifies the administration of repositories which is currently
done via the Gerrit UI instead of the CLI.

Bug: None
Change-Id: I0af3d77fb611e0c89dc455a5a215129b5c51c5ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5472843
Commit-Queue: Gavin Mak <gavinmak@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Auto-Submit: Alexander Schulze <alexschulze@chromium.org>

git_cl.py

@@ -1320,7 +1320,8 @@ class Changelist(object):
 
         self.branchref = branchref
         if self.branchref:
-            assert branchref.startswith(('refs/heads/', 'refs/branch-heads/'))
+            assert (branchref.startswith(('refs/heads/', 'refs/branch-heads/'))
+                    or branchref == 'refs/meta/config')
             self.branch = scm.GIT.ShortBranchName(self.branchref)
         else:
             self.branch = None

tests/git_cl_test.py

@@ -260,6 +260,30 @@ class TestGitClBasic(unittest.TestCase):
         self.assertFalse(hasattr(options, 'force'))
         self.assertFalse(hasattr(options, 'edit_description'))
 
+    def test_upload_to_meta_config_branch_no_retry(self):
+        m = mock.patch('git_cl.Changelist._CMDUploadChange',
+                       side_effect=[git_cl.GitPushError(), None]).start()
+        mock.patch('git_cl.Changelist.GetRemoteBranch',
+                   return_value=('foo', 'bar')).start()
+        mock.patch('git_cl.Changelist.GetGerritProject',
+                   return_value='foo').start()
+        mock.patch('git_cl.gerrit_util.GetProjectHead',
+                   return_value='refs/heads/main').start()
+
+        cl = git_cl.Changelist()
+        options = optparse.Values()
+        options.target_branch = 'refs/meta/config'
+        with self.assertRaises(SystemExitMock):
+            cl.CMDUploadChange(options, [], 'foo',
+                               git_cl.ChangeDescription('bar'))
+
+        # ensure upload is called once
+        self.assertEqual(len(m.mock_calls), 1)
+        sys.exit.assert_called_once_with(1)
+        # option not set as retry didn't happen
+        self.assertFalse(hasattr(options, 'force'))
+        self.assertFalse(hasattr(options, 'edit_description'))
+
     def test_upload_to_old_default_still_active(self):
         m = mock.patch('git_cl.Changelist._CMDUploadChange',
                        side_effect=[git_cl.GitPushError(), None]).start()