Automatically generate lists of source targets on Copybara export.

PiperOrigin-RevId: 448960624
diff --git a/WHITESPACE b/WHITESPACE
index 91b7478..f4b997f 100644
--- a/WHITESPACE
+++ b/WHITESPACE
@@ -1 +1,3 @@
-Edits in this file will cause a Copybara migration.
\ No newline at end of file
+Edits in this file will cause a Copybara migration.
+
+1 2 3 4 5
\ No newline at end of file