diff --git a/shared/get_public_rsync.sh b/shared/get_public_rsync.sh
index 86af335..ccba369 100755
--- a/shared/get_public_rsync.sh
+++ b/shared/get_public_rsync.sh
@@ -1,4 +1,5 @@
 #!/bin/sh
+# https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html
 set -u
 
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