tree_entry_interesting(): remove dependency on struct diff_options

tree_entry_interesting(): remove dependency on struct diff_options

This function can be potentially used in more places than just
tree-diff.c. "struct diff_options" does not make much sense outside
diff_tree_sha1().

While removing the use of diff_options, it also removes
tree_entry_extract() call, which means S_ISDIR() uses the entry->mode
directly, without being filtered by canon_mode() (called internally
inside tree_entry_extract).

The only use of the mode information in this function is to check the
type of the entry by giving it to S_ISDIR() macro, and the result does
not change with or without canon_mode(), so it is ok to bypass
tree_entry_extract().

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>