update-index: add test for chmod flags

update-index: add test for chmod flags

Currently there is no test checking the expected behaviour when multiple
chmod flags with different arguments are passed.  As argument handling
is not in line with other git commands it's easy to miss and
accidentally change the current behaviour.

While there, fix the argument type of chmod_path, which takes an int,
but had a char passed in.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>