We have a helper function test_ln_s_add that inserts a symbolic link
into the index even if the file system does not support symbolic links.
There is a small flaw in the emulation path: the added entry does not
pick up stat information of the fake symbolic link from the file system,
as a consequence, the index is not exactly the same as for the "regular"
path (where symbolic links are available). To fix this, just call
git update-index again.
This flaw was revealed by the earlier change that tightened
compare_diff_raw(), because a test case in t4008 depends on the
correctly updated index.
Signed-off-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>