t3030: Add a testcase for resolvable rename/add conflict with symlinks

t3030: Add a testcase for resolvable rename/add conflict with symlinks

d5af510 (RE: [PATCH] Avoid rename/add conflict when contents are identical
2010-09-01) avoided erroring out in a rename/add conflict when the contents
were identical.  A simpler fix could have handled that particular testcase,
but it would not correctly handle the case where a symlink is involved.
Add another testcase using symlinks, to avoid breaking that case.

Signed-off-by: Ken Schalk <ken.schalk@intel.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>