clone: copy hidden paths at local clone

clone: copy hidden paths at local clone

Make the copy_or_link_directory function no longer skip hidden
directories. This function, used to copy .git/objects, currently skips
all hidden directories but not hidden files, which is an odd behaviour.
The reason for that could be unintentional: probably the intention was
to skip '.' and '..' only but it ended up accidentally skipping all
directories starting with '.'. Besides being more natural, the new
behaviour is more permissive to the user.

Also adjust tests to reflect this behaviour change.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Co-authored-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>