Upgrade yesno() and make cp -i use it.
diff --git a/lib/lib.h b/lib/lib.h
index a695973..ab10eb7 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -109,7 +109,7 @@
 void replace_tempfile(int fdin, int fdout, char **tempname);
 void crc_init(unsigned int *crc_table, int little_endian);
 void terminal_size(unsigned *x, unsigned *y);
-int yesno(int def);
+int yesno(char *prompt, int def);
 void for_each_pid_with_name_in(char **names, void (*callback)(pid_t pid));