This can also be controlled by setting the GIT_WORK_TREE
environment variable and the core.worktree configuration
variable. It can be an absolute path or relative path to
the directory specified by --git-dir or GIT_DIR.
Note: If --git-dir or GIT_DIR are specified but none of
--work-tree, GIT_WORK_TREE and core.worktree is specified,
the current working directory is regarded as the top directory