int try_merge_command(const char *strategy, size_t xopts_nr,
const char **xopts, struct commit_list *common,
const char *head_arg, struct commit_list *remotes);
-int checkout_fast_forward(const unsigned char *from,
- const unsigned char *to,
+int checkout_fast_forward(const struct object_id *from,
+ const struct object_id *to,
int overwrite_ignore);