Make some adjustments to .summon and .group summon behavior to make t…

…hem more permissive:

- Now only requires the either target's group leader or target itself to be on your map
- Now summons all applicable group members even if one member fails checks
- No longer has some truly weird edge case instance unbind code that could cause exploit behavior (Really, I have no idea why this existed, because it certainly didn't do what it might've been meant to do.)

src/server/scripts/Commands/cs_group.cpp

@@ -65,7 +65,6 @@ public:
         if (!group)
         {
             handler->PSendSysMessage(LANG_NOT_IN_GROUP, nameLink.c_str());
-            handler->SetSentErrorMessage(true);
             return false;
         }
 
@@ -73,19 +72,22 @@ public:
         Group* gmGroup = gmPlayer->GetGroup();
         Map* gmMap = gmPlayer->GetMap();
         bool toInstance = gmMap->Instanceable();
+        bool onlyLocalSummon = false;
 
-        // we are in instance, and can summon only player in our group with us as lead
-        if (toInstance && (
-            !gmGroup || group->GetLeaderGUID() != gmPlayer->GetGUID() ||
-            gmGroup->GetLeaderGUID() != gmPlayer->GetGUID()))
-            // the last check is a bit excessive, but let it be, just in case
+        // make sure people end up on our instance of the map, disallow far summon if intended destination is different from actual destination
+        // note: we could probably relax this further by checking permanent saves and the like, but eh
+        // :close enough:
+        if (toInstance)
         {
-            handler->SendSysMessage(LANG_CANNOT_SUMMON_TO_INST);
-            handler->SetSentErrorMessage(true);
-            return false;
+            Player* groupLeader = ObjectAccessor::GetPlayer(gmMap, group->GetLeaderGUID());
+            if (!groupLeader || (groupLeader->GetMapId() != gmMap->GetId()) || (groupLeader->GetInstanceId() != gmMap->GetInstanceId()))
+            {
+                handler->SendSysMessage(LANG_PARTIAL_GROUP_SUMMON);
+                onlyLocalSummon = true;
+            }
         }
 
-        for (GroupReference* itr = group->GetFirstMember(); itr != NULL; itr = itr->next())
+        for (GroupReference* itr = group->GetFirstMember(); itr != nullptr; itr = itr->next())
         {
             Player* player = itr->GetSource();
 
@@ -94,27 +96,28 @@ public:
 
             // check online security
             if (handler->HasLowerSecurity(player, ObjectGuid::Empty))
-                return false;
+                continue;
 
             std::string plNameLink = handler->GetNameLink(player);
 
             if (player->IsBeingTeleported())
             {
                 handler->PSendSysMessage(LANG_IS_TELEPORTED, plNameLink.c_str());
-                handler->SetSentErrorMessage(true);
-                return false;
+                continue;
             }
 
             if (toInstance)
             {
                 Map* playerMap = player->GetMap();
 
-                if (playerMap->Instanceable() && playerMap->GetInstanceId() != gmMap->GetInstanceId())
+                if (
+                    (onlyLocalSummon || (playerMap->Instanceable() && playerMap->GetId() == gmMap->GetId())) && // either no far summon allowed or we're in the same map as player (no map switch)
+                    ((playerMap->GetId() != gmMap->GetId()) || (playerMap->GetInstanceId() != gmMap->GetInstanceId())) // so we need to be in the same map and instance of the map, otherwise skip
+                    )
                 {
                     // cannot summon from instance to instance
-                    handler->PSendSysMessage(LANG_CANNOT_SUMMON_TO_INST, plNameLink.c_str());
-                    handler->SetSentErrorMessage(true);
-                    return false;
+                    handler->PSendSysMessage(LANG_CANNOT_SUMMON_INST_INST, plNameLink.c_str());
+                    continue;
                 }
             }