sync: skip bloat check if fresh sync

Initial syncs won't have accumulated any garbage.

Bug: 379111283
Change-Id: I04b2ecde3e33f1f055038861a2705ab6aabb36d1
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/536083
Commit-Queue: Gavin Mak <gavinmak@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Tested-by: Gavin Mak <gavinmak@google.com>

subcmds/sync.py

diff --git a/subcmds/sync.py b/subcmds/sync.py
index eb71ae9..726e6d0 100644
--- a/subcmds/sync.py
+++ b/subcmds/sync.py
@@ -2110,7 +2110,8 @@
                 "experience, sync the entire tree."
             )
 
-        self._CheckForBloatedProjects(all_projects, opt)
+        if existing:
+            self._CheckForBloatedProjects(all_projects, opt)
 
         if not opt.quiet:
             print("repo sync has finished successfully.")