Get nebraska from git HEAD

autoupdate_EndToEndTest currently is fetching nebraska from the
devserver, but the devserver isn't being updated with new images anymore
so it's still serving an older version of nebraska. We need the latest
version to pick up fixes though, so always opt to get it from git HEAD.

BUG=b:205716602
TEST=test_that chromeos4-row7-rack11-host39 autoupdate_EndToEndTest --autotest_dir ~/trunk/src/third_party/autotest/files --args="update_type=delta source_release=14382.0.0 source_payload_uri=gs://chromeos-releases/dev-channel/cherry/14382.0.0/payloads/chromeos_14382.0.0_cherry_dev-channel_full_test.bin-gyywczdbha3wjkwpsipe5hzo5zbuw36i target_release=14382.0.0 target_payload_uri=gs://chromeos-releases/dev-channel/cherry/14382.0.0/payloads/chromeos_14382.0.0-14382.0.0_cherry_dev-channel_delta_test.bin-gyywczdbha3wi4pqmosksupuokistkmm"

Change-Id: I694972dd755aa5cdf6ba6c17eada90b5b750d6b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/3319337
Tested-by: Kyle Shimabukuro <kyleshima@chromium.org>
Reviewed-by: David Haddock <dhaddock@chromium.org>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: Derek Beckett <dbeckett@chromium.org>
Commit-Queue: David Haddock <dhaddock@chromium.org>
diff --git a/utils/frozen_chromite/lib/auto_updater_transfer.py b/utils/frozen_chromite/lib/auto_updater_transfer.py
index 9805bcd..7c1d22e 100644
--- a/utils/frozen_chromite/lib/auto_updater_transfer.py
+++ b/utils/frozen_chromite/lib/auto_updater_transfer.py
@@ -617,3 +617,16 @@
     cmd = ['curl', '-o', os.path.join(payload_dir, saved_filename),
            self._GetStagedUrl(payload_filename, build_id)]
     return cmd
+
+  def _TransferUpdateUtilsPackage(self):
+    """Transfer update-utils package to work directory of the remote device."""
+    logging.notice('Copying update script to device...')
+    source_dir = os.path.join(self._tempdir, 'src')
+    osutils.SafeMakedirs(source_dir)
+    nebraska_wrapper.RemoteNebraskaWrapper.GetNebraskaSrcFile(source_dir)
+
+    # Make sure the device.work_dir exists after any installation and reboot.
+    self._EnsureDeviceDirectory(self._device.work_dir)
+    # Python packages are plain text files.
+    self._device.CopyToWorkDir(source_dir, mode=_SCP, log_output=True,
+                               **self._cmd_kwargs)
diff --git a/utils/frozen_chromite/lib/nebraska_wrapper.py b/utils/frozen_chromite/lib/nebraska_wrapper.py
index 5a337d7..76a5d54 100644
--- a/utils/frozen_chromite/lib/nebraska_wrapper.py
+++ b/utils/frozen_chromite/lib/nebraska_wrapper.py
@@ -358,7 +358,7 @@
     else:
       # Download from googlesource.
       nebraska_url_path = '%s/+/%s/%s?format=text' % (
-          'chromiumos/platform/dev-util', 'refs/heads/master',
+          'chromiumos/platform/dev-util', 'refs/heads/main',
           'nebraska/nebraska.py')
       contents_b64 = gob_util.FetchUrl(constants.EXTERNAL_GOB_HOST,
                                        nebraska_url_path)