superproject: Don't update the commit ids of projects if remote is different.

1) Skip setting the revision id (commit id) for the projects whose
   remote doesn't match superproject's remote.
2) exp-superproject/superproject_override.xml includes local_manfiest's
   projects. When we load this XML, don't reload projects from local.xml
   (otherwise we will get duplicate projects errors).

Tested the code with the following commands.

$ ./run_tests -v

+ Test with local.xml
  $ repo_dev init -u sso://android.git.corp.google.com/platform/manifest -b master --use-superproject --partial-clone --clone-filter=blob:limit=10M && mkdir -p .repo/local_manifests && (gcertstatus -quiet=true || gcert) && ln -s /google/src/head/depot/google3/wireless/android/build_tools/aosp/manifests/mirror-aosp-master-with-vendor/local.xml  .repo/local_manifests/local.xml

  $ repo_dev sync -c -j8

+ Test without local.xml
  $ repo_dev init -u sso://android.git.corp.google.com/platform/manifest -b master --partial-clone --clone-filter=blob:limit=10M --repo-rev=main --use-superproject
  $ repo_dev sync -c -j8

Bug: [google internal] b/186395810
Change-Id: I4e9d4ac2d94a9fc0cef0ccd787b6310758009e86
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/304882
Tested-by: Raman Tenneti <rtenneti@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>

subcmds/sync.py

@@ -277,7 +277,7 @@ later is required to fix a server side protocol bug.
     """Returns True if current-branch or use-superproject options are enabled."""
     return opt.current_branch_only or self._UseSuperproject(opt)
 
-  def _UpdateProjectsRevisionId(self, opt, args):
+  def _UpdateProjectsRevisionId(self, opt, args, load_local_manifests):
     """Update revisionId of every project with the SHA from superproject.
 
     This function updates each project's revisionId with SHA from superproject.
@@ -287,6 +287,7 @@ later is required to fix a server side protocol bug.
       opt: Program options returned from optparse.  See _Options().
       args: Arguments to pass to GetProjects. See the GetProjects
           docstring for details.
+      load_local_manifests: Whether to load local manifests.
 
     Returns:
       Returns path to the overriding manifest file.
@@ -302,7 +303,7 @@ later is required to fix a server side protocol bug.
       print('error: Update of revsionId from superproject has failed',
             file=sys.stderr)
       sys.exit(1)
-    self._ReloadManifest(manifest_path)
+    self._ReloadManifest(manifest_path, load_local_manifests)
     return manifest_path
 
   def _FetchProjectList(self, opt, projects):
@@ -565,10 +566,18 @@ later is required to fix a server side protocol bug.
       t.join()
     pm.end()
 
-  def _ReloadManifest(self, manifest_name=None):
+  def _ReloadManifest(self, manifest_name=None, load_local_manifests=True):
+    """Reload the manfiest from the file specified by the |manifest_name|.
+
+    It unloads the manifest if |manifest_name| is None.
+
+    Args:
+      manifest_name: Manifest file to be reloaded.
+      load_local_manifests: Whether to load local manifests.
+    """
     if manifest_name:
       # Override calls _Unload already
-      self.manifest.Override(manifest_name)
+      self.manifest.Override(manifest_name, load_local_manifests=load_local_manifests)
     else:
       self.manifest._Unload()
 
@@ -857,8 +866,9 @@ later is required to fix a server side protocol bug.
     else:
       self._UpdateManifestProject(opt, mp, manifest_name)
 
+    load_local_manifests = not self.manifest.HasLocalManifests
     if self._UseSuperproject(opt):
-      manifest_name = self._UpdateProjectsRevisionId(opt, args)
+      manifest_name = self._UpdateProjectsRevisionId(opt, args, load_local_manifests)
 
     if self.gitc_manifest:
       gitc_manifest_projects = self.GetProjects(args,
@@ -926,7 +936,7 @@ later is required to fix a server side protocol bug.
       # Iteratively fetch missing and/or nested unregistered submodules
       previously_missing_set = set()
       while True:
-        self._ReloadManifest(manifest_name)
+        self._ReloadManifest(manifest_name, load_local_manifests)
         all_projects = self.GetProjects(args,
                                         missing_ok=True,
                                         submodules_ok=opt.fetch_submodules)