updating velvet chat template

Author: fbuciuni90

src/llama-chat.cpp

@@ -573,8 +573,11 @@ int32_t llm_chat_apply_template(
         // Velvet template
         std::string leading_space = "";
         std::string trailing_space = "";
-        bool trim_assistant_message = true;
+        bool trim_assistant_message = false;
         bool is_inside_turn = false;
+        std::string system_message = "";
+        std::string last_message(chat.back()->content);
+        ss << "<s>";
         for (auto message : chat) {
             if (!is_inside_turn) {
                 ss << leading_space << "<instruction>" << trailing_space;
@@ -583,9 +586,9 @@ int32_t llm_chat_apply_template(
             std::string role(message->role);
             std::string content(message->content);
             if (role == "system") {
-                ss << content << "\n\n";
+                system_message = content + "\n\n";
             } else if (role == "user") {
-                ss << content << leading_space << "</instruction>";
+                ss << (content==last_message ? system_message : "") << content << leading_space << "</instruction>";
             } else {
                 ss << trailing_space << (trim_assistant_message ? trim(content) : content) << "</s>";
                 is_inside_turn = false;