patch 8.0.0034
Problem:    No completion for ":messages".
Solution:   Complete "clear" argument. (Hirohito Higashi)
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 25a12be..5d098cc 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -4832,6 +4832,7 @@
 	{
 	    {EXPAND_COMMANDS, get_command_name, FALSE, TRUE},
 	    {EXPAND_BEHAVE, get_behave_arg, TRUE, TRUE},
+	    {EXPAND_MESSAGES, get_messages_arg, TRUE, TRUE},
 #ifdef FEAT_CMDHIST
 	    {EXPAND_HISTORY, get_history_arg, TRUE, TRUE},
 #endif