[BUG] source distributions do not preserve case in keys of setup.cfg

[aerusso]

setuptools version

HEAD (58.0.2)

Python version

(irrelevant)

OS

(irrelevant)

Additional environment information

No response

Description

When building a source tar.gz with python -m build, edit_config of setuptools is called to record information about the call in setup.cfg. During the rewrite, the case of the keys in the file is lost -- most notably, options.data_files loses the case of destination paths.

Expected behavior

The case of destination paths is preserved for data_files. More generally, all keys have their case preserved when building source tar.gzs

How to Reproduce

1. Create a setup.cfg with

[options.data_files]
cAsE=
  file
  file2

2. touch file file2
3. python3 -m build

Output

setup.cfg in the tar.gz loses the case: (extract with tar -xf dist/UNKNOWN-0.0.0.tar.gz && cat UNKNOWN-0.0.0/setup.cfg)

[options.data_files]
case = 
        file
        file2

[egg_info]
tag_build = 
tag_date = 0

Code of Conduct

• I agree to follow the PSF Code of Conduct

[jaraco]

I confirmed the finding.

Here's the stack when edit_config gets called:

  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/distutils/command/sdist.py", line 473, in make_distribution
    self.make_release_tree(base_dir, self.filelist.files)
  File "/Users/jaraco/code/public/pypa/setuptools/setuptools/command/sdist.py", line 158, in make_release_tree
    self.get_finalized_command('egg_info').save_version_info(dest)
  File "/Users/jaraco/code/public/pypa/setuptools/setuptools/command/egg_info.py", line 195, in save_version_info
    edit_config(filename, dict(egg_info=egg_info))
  File "/Users/jaraco/code/public/pypa/setuptools/setuptools/command/setopt.py", line 40, in edit_config

[jaraco]

Configparser converts keys to lowercase unless optionxform = lambda x: x.

[jaraco]

Oh, shoot. I just noticed you'd created a PR :/