Test that the rebase command updates the work tree as expected for
changes which don't result in conflicts. To make that work add two
helper functions that add a commit only touching files and then
revert it. This allows to rebase the target commit over these two
and to compare the result.
Set KNOWN_FAILURE_NOFF_MERGE_DOESNT_CREATE_EMPTY_SUBMODULE_DIR to
document that "replace directory with submodule" fails for an
interactive rebase because a directory "sub1" already exists.
Signed-off-by: Jens Lehmann <Jens.Lehmann@web.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>