The test was failing because it called 'git config --global core.excludesfile'
which returned the real user's gitignore path instead of using the test's
temp directory.
Fix: Set GIT_CONFIG_GLOBAL env var to an empty temp config file, ensuring
the test uses the temp directory's .config/git/ignore path as intended.
Also extracted the isolation logic into a reusable setupIsolatedGitConfig helper.
Co-authored-by: Ismar Iljazovic <ismar@gmail.com>
dc28efe9d1