rules.pl: refuse to submit commits that says DRAFT or DO NOT SUBMIT

rules.pl

diff --git a/rules.pl b/rules.pl
new file mode 100644
index 0000000..fd901e9
--- /dev/null
+++ b/rules.pl
@@ -0,0 +1,18 @@
+% We don't send email if the commit message says DRAFT, so don't allow submit either.
+submit_filter(In, Out) :-
+	In =.. [submit | I],
+	gerrit:commit_message_matches('DRAFT'),
+	!,
+	Error = label('Cannot-Submit-DRAFT-Commit', need(_)),
+	Out =.. [submit, Error | I].
+
+% Don't allow submit of DO NOT SUBMIT commit message either.
+submit_filter(In, Out) :-
+	In =.. [submit | I],
+	gerrit:commit_message_matches('DO NOT SUBMIT'),
+	!,
+	Error = label('Cannot-Submit-DO-NOT-SUBMIT-Commit', need(_)),
+	Out =.. [submit, Error | I].
+
+% Otherwise, pass submit rule through.
+submit_filter(In, Out) :- In = Out.