name-hash: properly fold directory names in adjust_dirname_case()
Correct the pointer arithmetic in adjust_dirname_case() so that it calls
find_dir_entry() with the correct string length. Previously passing in
"dir1/foo" would pass a length of 6 instead of the correct 4. This resulted in
find_dir_entry() never finding the entry and so the subsequent memcpy that would
fold the name to the version with the correct case never executed.
Add a test to validate the corrected behavior with name folding of directories.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>