interfaces: add a Protocol class for `scmutil.status` I initially tried moving this to the `interfaces` package, both to have more cleanly defined interfaces (interfaces shouldn't have to reach into implementation files for their type info), and because importing `mercurial.ui` either directly or indirectly into `interfaces.repository` causes a situation where pytype stops inferring the type for `revlogutils.constants` that are imported by `revlog`. (Likely this is caused by a cycle. The `dirstate` interface already imports `scmutil`, which in turn imports `ui`, so the `repository` interface module importing the `dirstate` interface module as part of converting those classes to Protocol classes will trigger the issue.) I gave up on moving the class because `scmutil.status` depends on `stringutil`, which has a surprisingly long tail of dependencies. In any event, a standalone Protocol class might help with the Rust code.

# util.py - Utilities for declaring interfaces.
#
# Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

# zope.interface imposes a run-time cost due to module import overhead and
# bookkeeping for declaring interfaces. So, we use stubs for various
# zope.interface primitives unless instructed otherwise.

from __future__ import annotations

if True:

    class Attribute:
        def __init__(self, __name__, __doc__=b''):
            pass

    class Interface:
        def __init__(
            self, name, bases=(), attrs=None, __doc__=None, __module__=None
        ):
            pass

    def implementer(*ifaces):
        def wrapper(cls):
            return cls

        return wrapper