Deprecation of dashes affects other project settings

[jaraco]

Hi! I checked https://setuptools.readthedocs.io/en/latest/history.html#v54-1-0 but I wasn't entirely clear: is this meant to warn for all keys using hyphens in setup.cfg? For example, I see warnings for these Flake8 options:

$ cat setup.cfg
[flake8]
extend-ignore = E203
max-line-length = 88

[isort]
profile = black

[tool:pytest]
addopts = -ra --color=yes
testpaths = Tests
$ python setup.py --version
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'extend-ignore' will not be supported in future versions. Please use the underscore name 'extend_ignore' instead
  warnings.warn(
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'max-line-length' will not be supported in future versions. Please use the underscore name 'max_line_length' instead
  warnings.warn(
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'extend-ignore' will not be supported in future versions. Please use the underscore name 'extend_ignore' instead
  warnings.warn(
/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/setuptools/dist.py:633: UserWarning: Usage of dash-separated 'max-line-length' will not be supported in future versions. Please use the underscore name 'max_line_length' instead
  warnings.warn(
8.2.0.dev0

Flake8 themselves say both underscores and hyphens are fine in setup.cfg:

https://flake8.pycqa.org/en/latest/user/configuration.html#project-configuration

Thanks!

Originally posted by @hugovk in #2588 (comment)

[jaraco]

Short answer, no. It was unintentional to affect config for other projects.