Change how display-message uses the client. Originally it was only

intended as the target client where the message should be displayed but
at some point (perhaps when -p was added), it was used for format
expansion too. This means it can get a bit weird where you have client
formats expanding for a client with a different current session than the
target session.

However, it is nice that display-message can be used to show information
about a specific client. So change so that the -c client will be used if
the session matches the target session (-t or default), otherwise the
best client will be chosen.

cmd-find.c

@@ -122,7 +122,7 @@ cmd_find_client_better(struct client *c, struct client *than)
 }
 
 /* Find best client for session. */
-static struct client *
+struct client *
 cmd_find_best_client(struct session *s)
 {
 	struct client	*c_loop, *c;