Git automatically treats certain directories as Git repositories when certain files are present. http://stackoverflow.com/questions/2044574/determine-if-directory-is-under-git-control

In normal circumstances, this happens for test repos that are kept inside git related repositories, e.g. https://github.com/schacon/grack/tree/613acd237ab7f522a02953c310aad0d484873bd7/tests/example

When there is a .git directory in the current directory, it takes precedence over the current directory being a bare repo: git commands without explicit --git-dir will use it.

If however git finds a directory that it recognizes to be a git bare repo and there is no .git, it will be used. Try git log in this directory. If some system fails to check for that, it is a great vector for arbitrary code execution.