oneway_diff: handle removed sparse directories

Update 'do_oneway_diff()' to perform a 'diff_tree_oid()' on removed sparse
directories, as it does for added or modified sparse directories (see
9eb00af562 (diff-lib: handle index diffs with sparse dirs, 2021-07-14)).

At the moment, this update is unreachable code because 'unpack_trees()'
(currently the only way 'oneway_diff()' can be called, via 'diff_cache()')
will always traverse trees down to the individual removed files of a deleted
sparse directory. A subsequent patch will change this to better preserve a
sparse index in other uses of 'unpack_tree()', e.g. 'git reset --hard'.
However, making that change without this patch would result in (among other
issues) 'git status' printing only the name of a deleted sparse directory,
not its contents. To avoid introducing that bug, 'do_oneway_diff()' is
updated before modifying 'unpack_trees()'.

Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions