Add warning when use existing - file for downloading output file

b2/console_tool.py

@@ -1369,11 +1369,13 @@ class DownloadFileMixin(
     MaxDownloadStreamsMixin,
     DownloadCommand,
 ):
-    @staticmethod
-    def correct_local_file_name(filename):
+    def correct_local_file_name(self, filename: str):
         if filename != '-':
             return filename
         if os.path.exists('-'):
+            self._print_stderr(
+                "WARNING: Filename `-` won't be supported in the future and will be treated as stdout alias."
+            )
             return filename
         return 'CON' if platform.system() == 'Windows' else '/dev/stdout'