extensions: add a default "*" suboptions prefix This is similar to what we do in other section (e.g. `paths`) and allow to change the behavior for all extensions. Sub options on individual extensions overwrite the default settings. Differential Revision: https://phab.mercurial-scm.org/D11823

[build-system]
requires = ["setuptools", "wheel"]

[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true