-extern int head_ref(int (*fn)(const char *path, const unsigned char *sha1));
-extern int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1));
-extern int for_each_tag_ref(int (*fn)(const char *path, const unsigned char *sha1));
-extern int for_each_branch_ref(int (*fn)(const char *path, const unsigned char *sha1));
-extern int for_each_remote_ref(int (*fn)(const char *path, const unsigned char *sha1));
+typedef int each_ref_fn(const char *refname, const unsigned char *sha1, void *cb_data);
+extern int head_ref(each_ref_fn, void *);
+extern int for_each_ref(each_ref_fn, void *);
+extern int for_each_tag_ref(each_ref_fn, void *);
+extern int for_each_branch_ref(each_ref_fn, void *);
+extern int for_each_remote_ref(each_ref_fn, void *);