-int head_ref_submodule(const char *submodule, each_ref_fn fn, void *cb_data);
-int for_each_ref_submodule(const char *submodule,
- each_ref_fn fn, void *cb_data);
-int for_each_ref_in_submodule(const char *submodule, const char *prefix,
- each_ref_fn fn, void *cb_data);
-int for_each_fullref_in_submodule(const char *submodule, const char *prefix,
- each_ref_fn fn, void *cb_data,
- unsigned int broken);
-int for_each_tag_ref_submodule(const char *submodule,
- each_ref_fn fn, void *cb_data);
-int for_each_branch_ref_submodule(const char *submodule,
- each_ref_fn fn, void *cb_data);
-int for_each_remote_ref_submodule(const char *submodule,
- each_ref_fn fn, void *cb_data);
-