Windows checkout fails on tests/fixtures/env/nul.env in v5.7.0 #619

Description
On Windows, Composer fails while installing vlucas/phpdotenv v5.7.0 from source. Git cannot check out the test fixture tests/fixtures/env/nul.env because NUL is a reserved Windows device name.

The file was added in v5.7.0: tests/fixtures/env/nul.env.

Steps to reproduce
Run composer update on Windows in a project that resolves vlucas/phpdotenv to v5.7.0.
Composer attempts to check out the package from source.

Actual result
Git checkout fails with:

error: invalid path 'tests/fixtures/env/nul.env'

Composer then reports that it failed to execute the Git checkout/reset for the package.

Expected result
Composer should be able to install the package on Windows, or the fixture should be named/stored in a way that does not prevent Windows checkouts.

Environment
OS: Windows Microsoft Windows 11 Pro, 10.0.26200 Build 26200
Composer version: 2.8.9 2025-05-13 14:01:37
PHP version: 8.4.7
phpdotenv: v5.7.0 (301c079)

Workaround
On Windows with Composer 2.10.3, composer install --prefer-dist completed successfully. It installed vlucas/phpdotenv v5.7.0 by extracting the distribution archive, avoiding the Git source checkout that fails on tests/fixtures/env/nul.env.