dir-iterator: add flags parameter to dir_iterator_begin
Add the possibility of giving flags to dir_iterator_begin to initialize
a dir-iterator with special options.
Currently possible flags are:
- DIR_ITERATOR_PEDANTIC, which makes dir_iterator_advance abort
immediately in the case of an error, instead of keep looking for the
next valid entry;
- DIR_ITERATOR_FOLLOW_SYMLINKS, which makes the iterator follow
symlinks and include linked directories' contents in the iteration.
These new flags will be used in a subsequent patch.
Also add tests for the flags' usage and adjust refs/files-backend.c to
the new dir_iterator_begin signature.
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>