patch 7.4.2263
Problem:    :filter does not work for many commands.  Can only get matching
            messages.
Solution:   Make :filter work for :command, :map, :list, :number and :print.
            Make ":filter!" show non-matching lines.
diff --git a/src/message.c b/src/message.c
index f24bc28..0d10431 100644
--- a/src/message.c
+++ b/src/message.c
@@ -2161,8 +2161,12 @@
     int
 message_filtered(char_u *msg)
 {
-    return cmdmod.filter_regmatch.regprog != NULL
-		     && !vim_regexec(&cmdmod.filter_regmatch, msg, (colnr_T)0);
+    int match;
+
+    if (cmdmod.filter_regmatch.regprog == NULL)
+	return FALSE;
+    match = vim_regexec(&cmdmod.filter_regmatch, msg, (colnr_T)0);
+    return cmdmod.filter_force ? match : !match;
 }
 
 /*