Revert "Use --unset to remove the credentials store from the git config"
running :

    git config --local foo.bar qix
    git config --local --unset foo.bar
    git config --local foo.bar qix

result in (unexpected) dublicate [foo] section. Looks like a git bug.

This reverts commit 0390acb4c5af51cbc62359122d6719a95dfb452c.