In ac8acb4 (sparse-index: complete partial expansion, 2022-05-23),
'expand_index()' was updated to expand the index to a given pathspec.
However, the 'path_matches_pattern_list()' method used to facilitate this
has the side effect of initializing or updating the index hash variables
('name_hash', 'dir_hash', and 'name_hash_initialized'). This operation is
performed on 'istate', though, not 'full'; as a result, the initialized
hashes are later overwritten when copied from 'full'. To ensure the correct
hashes are in 'istate' after the index expansion, change the arg used in
'path_matches_pattern_list()' from 'istate' to 'full'.

Note that this does not fully solve the problem. If 'istate' does not have
an initialized 'name_hash' when its contents are copied to 'full',
initialized hashes will be copied back into 'istate' but
'name_hash_initialized' will be 0. Therefore, we also need to copy
'full->name_hash_initialized' back to 'istate' after the index expansion is
complete.

Signed-off-by: Victoria Dye <vdye@github.com>

Add a test verifying that sparse-checkout (with and without sparse index
enabled) treat untracked files & directories correctly when changing sparse
patterns. Specifically, it ensures that 'git sparse-checkout set'

* deletes empty directories outside the sparse cone
* does _not_ delete untracked files outside the sparse cone

Signed-off-by: Victoria Dye <vdye@github.com>