Excise old justification when duplicate is made

This is a POC that makes the unit test pass. Still need to spruce up the output
and restrict the excision to only o-supported productions.

See #529

Core/SoarKernel/src/decision_process/rete.cpp

@@ -3808,12 +3808,19 @@ byte add_production_to_rete(agent* thisAgent, production* p, condition* lhs_top,
             output << "\nIgnoring "
                    << p->name->to_string(true)
                    << " because it is a duplicate of "
-                   << p_node->b.p.prod->name->to_string(true)
+                   << duplicate_rule->name->to_string(true)
                    << " ";
             xml_generate_warning(thisAgent, output.str().c_str());
 
             thisAgent->outputManager->printa_sf(thisAgent, "Ignoring %y because it is a duplicate of %y\n",
-                               p->name, p_node->b.p.prod->name);
+                               p->name, duplicate_rule->name);
+        }
+        // TODO: only excise previous if o-supported
+        // TODO: reorganize and fix outputs; should not say it's ignoring the justification, but should say previous is being excised.
+        if (p->type == JUSTIFICATION_PRODUCTION_TYPE) {
+            thisAgent->outputManager->printa_sf(thisAgent, "Excising existing duplicate justification %y to replace with %y\n", duplicate_rule->name, p->name);
+            excise_production_from_rete(thisAgent, duplicate_rule);
+            break;
         }
         thisAgent->symbolManager->deallocate_symbol_list_removing_references(rhs_unbound_vars_for_new_prod);
         return DUPLICATE_PRODUCTION;