t0612: add tests to exercise Git/JGit reftable compatibility
While the reftable format is a recent introduction in Git, JGit already
knows to read and write reftables since 2017. Given the complexity of
the format there is a very real risk of incompatibilities between those
two implementations, which is something that we really want to avoid.
Add some basic tests that verify that reftables written by Git and JGit
can be read by the respective other implementation. For now this test
suite is rather small, only covering basic functionality. But it serves
as a good starting point and can be extended over time.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>