* `head_ref_submodule()`, `for_each_ref_submodule()`,
`for_each_ref_in_submodule()`, `for_each_tag_ref_submodule()`,
`for_each_branch_ref_submodule()`, `for_each_remote_ref_submodule()`
- do the same as the functions descibed above but for a specified
+ do the same as the functions described above but for a specified
submodule.
* `for_each_rawref()` can be used to learn about broken ref and symref.