add config.chat_template to be able to customize the chat file banner

lua/gp/config.lua

@@ -102,6 +102,20 @@ local config = {
 	-- just a static string is legacy and the [{{agent}}] element is added automatically
 	-- if you really want just a static string, make it a table with one element { "🤖:" }
 	chat_assistant_prefix = { "🤖:", "[{{agent}}]" },
+	-- The banner shown at the top of each chat file.
+	chat_template = [[
+# topic: ?
+
+- file: %s
+%s
+Write your queries after %s. Use `%s` or :%sChatRespond to generate a response.
+Response generation can be terminated by using `%s` or :%sChatStop command.
+Chats are saved automatically. To delete this chat, use `%s` or :%sChatDelete.
+Be cautious of very long chats. Start a fresh chat by using `%s` or :%sChatNew.
+
+---
+
+%s]],
 	-- chat topic generation prompt
 	chat_topic_gen_prompt = "Summarize the topic of our conversation above"
 		.. " in two or three words. Respond only with those words.",

lua/gp/init.lua

@@ -1675,7 +1675,7 @@ M.new_chat = function(params, model, system_prompt, toggle)
 	end
 
 	local template = string.format(
-		M.chat_template,
+		M.config.chat_template or M.chat_template,
 		string.match(filename, "([^/]+)$"),
 		model .. system_prompt,
 		M.config.chat_user_prefix,