[Updater] Optionally commit and upload change

Test: ./updater.sh update --force --branch_and_commit --push_change googletest
Test: aosp/889542
Change-Id: I1025e2ded65000ce34e2f02f84052e7871e425d3
diff --git a/git_updater.py b/git_updater.py
index 81ef922..81ee93d 100644
--- a/git_updater.py
+++ b/git_updater.py
@@ -135,7 +135,8 @@
             print('{} is {} commits behind of {}.'.format(
                 self.merge_from, len(commits), upstream_branch))
 
-        self._write_metadata(self.proj_path)
         print("Running `git merge {merge_branch}`..."
               .format(merge_branch=self.merge_from))
         git_utils.merge(self.proj_path, self.merge_from)
+        self._write_metadata(self.proj_path)
+        git_utils.add_file(self.proj_path, 'METADATA')