Update chat handling to clear chat and show help; small fix to /export (#826)

* Update chat handling

(1) Make sure to use the `chat_history` prefix in the filename if none is supplied and not use a blank string on double `<Enter>`

(2) When using `/clear` clear the entire chat but show the help menu.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: srdas

packages/jupyter-ai/jupyter_ai/chat_handlers/clear.py

@@ -6,6 +6,8 @@
 
 
 class ClearChatHandler(BaseChatHandler):
+    """Clear the chat panel and show the help menu"""
+
     id = "clear"
     name = "Clear chat messages"
     help = "Clear the chat window"
@@ -17,10 +19,15 @@ def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
 
     async def process_message(self, _):
+        tmp_chat_history = self._chat_history[0]
         self._chat_history.clear()
         for handler in self._root_chat_handlers.values():
             if not handler:
                 continue
 
             handler.broadcast_message(ClearMessage())
+
+            self._chat_history = [tmp_chat_history]
+            self.reply(tmp_chat_history.body)
+
             break

packages/jupyter-ai/jupyter_ai/chat_handlers/export.py

@@ -35,7 +35,9 @@ async def process_message(self, message: HumanChatMessage):
             self.chat_message_to_markdown(msg) for msg in self._chat_history
         )
         args = self.parse_args(message)
-        chat_filename = args.path[0] if args.path else "chat_history"
+        chat_filename = (
+            args.path[0] if (args.path and args.path[0] != "") else "chat_history"
+        )  # Handles both empty args and double tap <Enter> key
         chat_filename = f"{chat_filename}-{datetime.now():%Y-%m-%d-%H-%M}.md"
         chat_file = os.path.join(self.root_dir, chat_filename)
         with open(chat_file, "w") as chat_history: