fast-import is able to write imported tree objects in delta format.
It holds a tree structure in memory where each tree entry may have
a delta base sha1 assigned. When delta base data is needed it is
reconstructed from this in-memory structure. Though sometimes the
delta base data doesn't match the delta base sha1 so wrong or even
corrupt pack is produced.
Add a small test that produces a corrupt pack. It uses just tree
copy and file modification commands aside from the very basic commit
and blob commands.
Signed-off-by: Dmitry Ivankov <divanorama@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>