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

Fixes to sparse index compatibility work for "reset" and "checkout"
commands.

* vd/sparse-reset-checkout-fixes:
  unpack-trees: unpack new trees as sparse directories
  cache.h: create 'index_name_pos_sparse()'
  oneway_diff: handle removed sparse directories
  checkout: fix nested sparse directory diff in sparse index

diff --cc builtin/checkout.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc read-cache.c
Simple merge

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

diff --cc unpack-trees.c
Simple merge