Allow server admins to require that a display nick drops last.

Closes #348.

data/anope.example.conf

@@ -746,6 +746,7 @@ log
  *  nickserv/cert                 - Can modify other users certificate lists
  *  nickserv/confirm              - Can confirm other users nicknames
  *  nickserv/drop                 - Can drop other users nicks
+ *  nickserv/drop/display         - Allows dropping display nicks when preservedisplay is enabled
  *  nickserv/drop/override        - Allows dropping nicks without using a confirmation code
  *  nickserv/recover              - Can recover other users nicks
  *  operserv/config               - Can modify services's configuration

data/nickserv.example.conf

@@ -219,6 +219,12 @@ module
 	 * This directive is optional. If not set it defaults to 50.
 	 */
 	maxpasslen = 50
+
+	/*
+	 * Whether all of the secondary nicks of a nick group have to expire or be
+	  dropped before the display nick can expire or be dropped.
+	 */
+	preservedisplay = no
 }
 
 /*

modules/nickserv/nickserv.cpp

@@ -536,6 +536,9 @@ public:
 			if (nickserv_expire && Anope::CurTime - na->last_seen >= nickserv_expire)
 				expire = true;
 
+			if (na->nc->na == na && na->nc->aliases->size() > 1 && Config->GetModule("nickserv")->Get<bool>("preservedisplay"))
+				expire = false;
+
 			FOREACH_MOD(OnPreNickExpire, (na, expire));
 
 			if (expire)

modules/nickserv/ns_drop.cpp

@@ -57,6 +57,12 @@ public:
 			return;
 		}
 
+		if (na->nc->na == na && na->nc->aliases->size() > 1 && Config->GetModule("nickserv")->Get<bool>("preservedisplay") && !source.HasPriv("nickserv/drop/display"))
+		{
+			source.Reply(_("You may not drop \002%s\002 as it is the display nick for the account."), na->nick.c_str());
+			return;
+		}
+
 		auto *code = dropcode.Get(na);
 		if (params.size() < 2 || ((!code || !code->equals_ci(params[1])) && (!source.HasPriv("nickserv/drop/override") || params[1] != "OVERRIDE")))
 		{