add BufferPane::clear()

src/gui/BufferPane.cc

@@ -749,3 +749,9 @@ void BufferPane::set_command_mode()
     set_show_status_bar(false);
     enter_insert_mode(Window::EnterInsertModeMode::START_OF_CHAR);
 }
+
+void BufferPane::clear()
+{
+    m_buffer->clear();
+    *m_iterator = m_buffer->begin();
+}

src/gui/BufferPane.h

@@ -34,6 +34,7 @@ public:
     {
         m_focused = focused;
     }
+    void clear();
 
 protected:
     int effective_scroll_offset()