[V3] --token and --no-instance flags (#1872)

* Ability to run Red with token without instance

* --no-instance flag

* Reformatted cli with black

* Fix changes requested by @Tobotimus

- Use "system reboot" to be clearer
- save_default_config renamed to create_temp_config
- More documentation for the create_temp_config function

* Update create_temp_config call

* Fix up imports

redbot/core/cli.py

@@ -138,6 +138,16 @@ def parse_cli_flags(args):
         action="store_true",
         help="Enables the built-in RPC server. Please read the docs prior to enabling this!",
     )
+    parser.add_argument("--token", type=str, help="Run Red with the given token.")
+    parser.add_argument(
+        "--no-instance",
+        action="store_true",
+        help=(
+            "Run Red without any existing instance. "
+            "The data will be saved under a temporary folder "
+            "and deleted on next system restart."
+        ),
+    )
     parser.add_argument(
         "instance_name", nargs="?", help="Name of the bot instance created during `redbot-setup`."
     )

redbot/core/data_manager.py

@@ -2,15 +2,18 @@ import sys
 import os
 from pathlib import Path
 from typing import List
+from copy import deepcopy
 import hashlib
 import shutil
 import logging
 
 import appdirs
+import tempfile
 
 from .json_io import JsonIO
 
 __all__ = [
+    "create_temp_config",
     "load_basic_configuration",
     "cog_data_path",
     "core_data_path",
@@ -39,6 +42,26 @@ if not config_dir:
 config_file = config_dir / "config.json"
 
 
+def create_temp_config():
+    """
+    Creates a default instance for Red, so it can be ran
+    without creating an instance.
+
+    .. warning:: The data of this instance will be removed
+        on next system restart.
+    """
+    name = "temporary_red"
+
+    default_dirs = deepcopy(basic_config_default)
+    default_dirs["DATA_PATH"] = tempfile.mkdtemp()
+    default_dirs["STORAGE_TYPE"] = "JSON"
+    default_dirs["STORAGE_DETAILS"] = {}
+
+    config = JsonIO(config_file)._load_json()
+    config[name] = default_dirs
+    JsonIO(config_file)._save_json(config)
+
+
 def load_basic_configuration(instance_name_: str):
     """Loads the basic bootstrap configuration necessary for `Config`
     to know where to store or look for data.