setup_git_directory_gently contract question?

    Is the function setup_git_directory_gently supposed to change the
current working directory, or should it keep the initial one?
    What is the meaning of nongit_ok?

    Because if I use nongit_ok != NULL, but *nongit_ok == 1, this
function changes the current working directory to the top of the
worktree directory.

    Thanks,
    Ciprian Craciun.