diffmanifests/sync: simplify repodir lookup

We have access to repodir on the command object itself, so we don't
need to pull it indirectly out of the manifest object.

Change-Id: I8688fb1c84979825efa966dc787e78c6f7ba3823
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/296542
Reviewed-by: Raman Tenneti <rtenneti@google.com>
Tested-by: Mike Frysinger <vapier@google.com>
diff --git a/subcmds/sync.py b/subcmds/sync.py
index 5855af5..5020ea7 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -680,7 +680,7 @@
       if project.relpath:
         new_project_paths.append(project.relpath)
     file_name = 'project.list'
-    file_path = os.path.join(self.manifest.repodir, file_name)
+    file_path = os.path.join(self.repodir, file_name)
     old_project_paths = []
 
     if os.path.exists(file_path):