Apply suggestions from the review

httpie/manager/cli.py

@@ -4,7 +4,7 @@ from httpie import __version__
 
 CLI_SESSION_UPGRADE_FLAGS = [
     {
-        'variadic': ['--bind-cookies'],
+        'flags': ['--bind-cookies'],
         'action': 'store_true',
         'default': False,
         'help': 'Bind domainless cookies to the host that session belongs.'
@@ -102,8 +102,8 @@ def generate_subparsers(root, parent_parser, definitions):
 
         for argument in properties:
             argument = argument.copy()
-            variadic = argument.pop('variadic', [])
-            command_parser.add_argument(*variadic, **argument)
+            flags = argument.pop('flags', [])
+            command_parser.add_argument(*flags, **argument)
 
 
 parser = HTTPieManagerArgumentParser(

httpie/manager/tasks.py

@@ -1,9 +1,10 @@
 import argparse
 from typing import TypeVar, Callable, Tuple
 
-from httpie.sessions import SESSIONS_DIR_NAME, Session, get_httpie_session
+from httpie.sessions import SESSIONS_DIR_NAME, get_httpie_session
 from httpie.status import ExitStatus
 from httpie.context import Environment
+from httpie.legacy import cookie_format as legacy_cookies
 from httpie.manager.cli import missing_subcommand, parser
 
 T = TypeVar('T')
@@ -51,27 +52,8 @@ def is_version_greater(version_1: str, version_2: str) -> bool:
     return split_version(version_1) > split_version(version_2)
 
 
-def fix_cookie_layout(session: Session, hostname: str, args: argparse.Namespace) -> None:
-    if not isinstance(session['cookies'], dict):
-        return None
-
-    session['cookies'] = [
-        {
-            'name': key,
-            **value
-        }
-        for key, value in session['cookies'].items()
-    ]
-    for cookie in session.cookies:
-        if cookie.domain == '':
-            if args.bind_cookies:
-                cookie.domain = hostname
-            else:
-                cookie._rest['is_explicit_none'] = True
-
-
 FIXERS_TO_VERSIONS = {
-    '3.1.0': fix_cookie_layout
+    '3.1.0': legacy_cookies.fix_layout
 }