Merge branch 'vd/sparse-reset-checkout-fixes'

Segfault fix-up to an earlier fix to the topic to teach "git reset"
and "git checkout" work better in a sparse checkout.

* vd/sparse-reset-checkout-fixes:
  unpack-trees: fix sparse directory recursion check

diff --cc t/t1092-sparse-checkout-compatibility.sh
Simple merge

diff --cc unpack-trees.c
Simple merge