extern int read_index_from(struct index_state *, const char *path);
extern int is_index_unborn(struct index_state *);
extern int read_index_unmerged(struct index_state *);
-extern int write_index(const struct index_state *, int newfd);
+extern int write_index(struct index_state *, int newfd);
extern int discard_index(struct index_state *);
extern int unmerged_index(const struct index_state *);
extern int verify_path(const char *path);