filter-branch: Add tests for submodules in tree-filter
Add tests to make sure that:
1) a submodule can be removed and its content replaced with regular files
('rewrite submodule with another content'). This test passes only with
the previous patch applied.
2) it is possible to replace submodule revision by direct index
manipulation ('replace submodule revision'). Although it would be
better to run such a filter in --index-filter, this test shows that
this functionality is not broken by the previous patch. This succeeds
both with and without the previous patch.
Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>