repopick: Use project revision if available

* Fixes repopicking from repos synced under multiple paths + branches.

Change-Id: Icb165f3d9df67f1b11304e8d7ed955464dcb57bc

build/tools/repopick.py

@@ -268,7 +268,7 @@ if __name__ == '__main__':
                 if remote.get('name') == project.get('remote'):
                     revision = remote.get('revision')
             if revision is None:
-                revision = default_revision
+                revision = project.get('revision', default_revision)
 
         if name not in project_name_to_data:
             project_name_to_data[name] = {}