diff --git a/git_command.py b/git_command.py
index 04953f3..95db91f 100644
--- a/git_command.py
+++ b/git_command.py
@@ -75,7 +75,8 @@
     proj = os.path.dirname(os.path.abspath(__file__))
     env[GIT_DIR] = os.path.join(proj, '.git')
     result = subprocess.run([GIT, 'describe', HEAD], stdout=subprocess.PIPE,
-                            encoding='utf-8', env=env, check=False)
+                            stderr=subprocess.DEVNULL, encoding='utf-8',
+                            env=env, check=False)
     if result.returncode == 0:
       ver = result.stdout.strip()
       if ver.startswith('v'):
diff --git a/git_config.py b/git_config.py
index 978f6a5..3eaf201 100644
--- a/git_config.py
+++ b/git_config.py
@@ -65,6 +65,15 @@
 
   _USER_CONFIG = '~/.gitconfig'
 
+  _ForSystem = None
+  _SYSTEM_CONFIG = '/etc/gitconfig'
+
+  @classmethod
+  def ForSystem(cls):
+    if cls._ForSystem is None:
+      cls._ForSystem = cls(configfile=cls._SYSTEM_CONFIG)
+    return cls._ForSystem
+
   @classmethod
   def ForUser(cls):
     if cls._ForUser is None:
@@ -356,7 +365,10 @@
     return c
 
   def _do(self, *args):
-    command = ['config', '--file', self.file, '--includes']
+    if self.file == self._SYSTEM_CONFIG:
+      command = ['config', '--system', '--includes']
+    else:
+      command = ['config', '--file', self.file, '--includes']
     command.extend(args)
 
     p = GitCommand(None,
diff --git a/git_superproject.py b/git_superproject.py
index 0c47706..2a47847 100644
--- a/git_superproject.py
+++ b/git_superproject.py
@@ -23,11 +23,14 @@
 """
 
 import hashlib
+import functools
 import os
 import sys
+import time
 from typing import NamedTuple
 
 from git_command import git_require, GitCommand
+from git_config import RepoConfig
 from git_refs import R_HEADS
 from manifest_xml import LOCAL_MANIFEST_GROUP_PREFIX
 
@@ -343,3 +346,81 @@
 
     manifest_path = self._WriteManfiestFile()
     return UpdateProjectsResult(manifest_path, False)
+
+
+@functools.lru_cache(maxsize=None)
+def _UseSuperprojectFromConfiguration():
+  """Returns the user choice of whether to use superproject."""
+  user_cfg = RepoConfig.ForUser()
+  system_cfg = RepoConfig.ForSystem()
+  time_now = int(time.time())
+
+  user_value = user_cfg.GetBoolean('repo.superprojectChoice')
+  if user_value is not None:
+    user_expiration = user_cfg.GetInt('repo.superprojectChoiceExpire')
+    if user_expiration is not None and (user_expiration <= 0 or user_expiration >= time_now):
+      # TODO(b/190688390) - Remove prompt when we are comfortable with the new
+      # default value.
+      print(('You are currently enrolled in Git submodules experiment '
+             '(go/android-submodules-quickstart).  Use --no-use-superproject '
+             'to override.\n'), file=sys.stderr)
+    return user_value
+
+  # We don't have an unexpired choice, ask for one.
+  system_value = system_cfg.GetBoolean('repo.superprojectChoice')
+  if system_value:
+    # The system configuration is proposing that we should enable the
+    # use of superproject. Present this to user for confirmation if we
+    # are on a TTY, or, when we are not on a TTY, accept the system
+    # default for this time only.
+    #
+    # TODO(b/190688390) - Remove prompt when we are comfortable with the new
+    # default value.
+    prompt = ('Repo can now use Git submodules (go/android-submodules-quickstart) '
+              'instead of manifests to represent the state of the Android '
+              'superproject, which results in faster syncs and better atomicity.\n\n')
+    if sys.stdout.isatty():
+      prompt += 'Would you like to opt in for two weeks (y/N)? '
+      response = input(prompt).lower()
+      time_choiceexpire = time_now + (86400 * 14)
+      if response in ('y', 'yes'):
+        userchoice = True
+      elif response in ('a', 'always'):
+        userchoice = True
+        time_choiceexpire = 0
+      elif response == 'never':
+        userchoice = False
+        time_choiceexpire = 0
+      elif response in ('n', 'no'):
+        userchoice = False
+      else:
+        # Unrecognized user response, assume the intention was no, but
+        # only for 2 hours instead of 2 weeks to balance between not
+        # being overly pushy while still retain the opportunity to
+        # enroll.
+        userchoice = False
+        time_choiceexpire = time_now + 7200
+
+      user_cfg.SetString('repo.superprojectChoiceExpire', str(time_choiceexpire))
+      user_cfg.SetBoolean('repo.superprojectChoice', userchoice)
+
+      return userchoice
+    else:
+      print('Accepting once since we are not on a TTY', file=sys.stderr)
+      return True
+
+  # For all other cases, we would not use superproject by default.
+  return False
+
+
+def UseSuperproject(opt, manifest):
+  """Returns a boolean if use-superproject option is enabled."""
+
+  if opt.use_superproject is not None:
+    return opt.use_superproject
+  else:
+    client_value = manifest.manifestProject.config.GetBoolean('repo.superproject')
+    if client_value is not None:
+      return client_value
+    else:
+      return _UseSuperprojectFromConfiguration()
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 8d89cf7..8defc93 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -278,16 +278,9 @@
       branch = branch[len(R_HEADS):]
     return branch
 
-  def _UseSuperproject(self, opt):
-    """Returns True if use-superproject option is enabled"""
-    if opt.use_superproject is not None:
-      return opt.use_superproject
-    else:
-      return self.manifest.manifestProject.config.GetBoolean('repo.superproject')
-
   def _GetCurrentBranchOnly(self, opt):
     """Returns True if current-branch or use-superproject options are enabled."""
-    return opt.current_branch_only or self._UseSuperproject(opt)
+    return opt.current_branch_only or git_superproject.UseSuperproject(opt, self.manifest)
 
   def _UpdateProjectsRevisionId(self, opt, args, load_local_manifests):
     """Update revisionId of every project with the SHA from superproject.
@@ -964,7 +957,7 @@
       self._UpdateManifestProject(opt, mp, manifest_name)
 
     load_local_manifests = not self.manifest.HasLocalManifests
-    if self._UseSuperproject(opt):
+    if git_superproject.UseSuperproject(opt, self.manifest):
       new_manifest_name = self._UpdateProjectsRevisionId(opt, args, load_local_manifests)
       if not new_manifest_name:
         manifest_name = new_manifest_name