extern int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
const char *base, struct diff_options *opt);
extern int diff_tree_sha1(const unsigned char *old, const unsigned char *new,
extern int diff_tree(struct tree_desc *t1, struct tree_desc *t2,
const char *base, struct diff_options *opt);
extern int diff_tree_sha1(const unsigned char *old, const unsigned char *new,