sync: Add CLI flag for globally disabling submodule fetch

A global setting for disabling fetching of submodules is useful
since this can currently otherwise only be done by modifying
the manifest, or by explicitly providing projects on command line.

Add this setting as --no-fetch-submodules to mirror the existing
--fetch-submodules.

Change-Id: Ic727c54f11a594aa52315751284b87138cf246bb
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/607641
Commit-Queue: Josef Malmstrom <Josef.Malmstrom@arm.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Tested-by: Josef Malmstrom <Josef.Malmstrom@arm.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

command.py

@@ -17,6 +17,7 @@ import multiprocessing
 import optparse
 import os
 import re
+from typing import TYPE_CHECKING
 
 from error import InvalidProjectGroupsError
 from error import NoSuchProjectError
@@ -25,6 +26,10 @@ from event_log import EventLog
 import progress
 
 
+if TYPE_CHECKING:
+    from project import Project
+
+
 # Are we generating man-pages?
 GENERATE_MANPAGES = os.environ.get("_REPO_GENERATE_MANPAGES_") == " indeed! "
 
@@ -375,7 +380,7 @@ class Command:
         manifest=None,
         groups="",
         missing_ok=False,
-        submodules_ok=False,
+        submodules_ok=None,
         all_manifests=False,
     ):
         """A list of projects that match the arguments.
@@ -385,7 +390,9 @@ class Command:
             manifest: an XmlManifest, the manifest to use, or None for default.
             groups: a string, the manifest groups in use.
             missing_ok: a boolean, whether to allow missing projects.
-            submodules_ok: a boolean, whether to allow submodules.
+            submodules_ok: whether to allow submodules. True allows them for
+                all projects, False disallows them for all projects, and None
+                defers to each project's sync-s setting.
             all_manifests: a boolean, if True then all manifests and
                 submanifests are used. If False, then only the local
                 (sub)manifest is used.
@@ -403,6 +410,11 @@ class Command:
             all_projects_list = manifest.projects
         result = []
 
+        def should_include_submodules(project: "Project") -> bool:
+            if submodules_ok is None:
+                return project.sync_s
+            return submodules_ok
+
         if not groups:
             groups = manifest.GetManifestGroupsStr()
         groups = [x for x in re.split(r"[,\s]+", groups) if x]
@@ -410,7 +422,7 @@ class Command:
         if not args:
             derived_projects = {}
             for project in all_projects_list:
-                if submodules_ok or project.sync_s:
+                if should_include_submodules(project):
                     derived_projects.update(
                         (p.RelPath(local=False), p)
                         for p in project.GetDerivedSubprojects()
@@ -452,7 +464,7 @@ class Command:
                     if (
                         project
                         and not project.Derived
-                        and (submodules_ok or project.sync_s)
+                        and should_include_submodules(project)
                     ):
                         search_again = False
                         for subproject in project.GetDerivedSubprojects():