Add the ability to administratively enroll repo into using superproject.

Repo will remember a choice and an expiration time of the choice, per
user, about whether to use superproject by default. When not specified
from command line and the choice is not expired, repo would use the
user default value.

When a user default value is not present and when the system wide
enable default is provided in git's system configuration, repo would
ask the user for a confirmation which will be valid for two weeks.

git_config.py: Add support for system config. When reading system
	config, we would use --system to avoid hardcoding a path as the
	value may be different on some other distributions.

git_superproject.py: Add a new subroutine, _UseSuperproject(), which
	returns whether superproject should be used and whether it
	is from a user configuration.

	The value is determined in the following order:

	1. If the user specifies either --use-superproject or
	--no-use-superproject, then that choice is being used.

	2. If neither is specified, we would then check the saved value
	(upon repo init) and use that choice when there was a choice.

	3. We then check if there is a saved and unexpired value for
	user's choice in their ~/.gitconfig, and use the unexpired
	choice, if available.

	4. Finally, if all the above didn't give us a decision, and if
	the git system configuration is providing a rollout hint, present
	a prompt to user for their decision and save it in ~/.gitconfig.

subcmds/sync.py: Make use of the new UseSuperproject() provided by
git_superproject.py.

While there also silent stderr from git describe when determining the
version of repo.

Bug: [google internal] b/190688390
Change-Id: Iad3ee03026342ee500e5d65e2f0fa600d7637613
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/309762
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Xin Li <delphij@google.com>

git_command.py

@@ -75,7 +75,8 @@ def RepoSourceVersion():
     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'):

git_config.py

@@ -65,6 +65,15 @@ class GitConfig(object):
 
   _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 @@ class GitConfig(object):
     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,

git_superproject.py

@@ -23,11 +23,14 @@ Examples:
 """
 
 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 @@ class Superproject(object):
 
     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()

subcmds/sync.py

@@ -278,16 +278,9 @@ later is required to fix a server side protocol bug.
       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 @@ later is required to fix a server side protocol bug.
       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