upstream_base_url = http://downloads.xiph.org/releases/$(upstream_source_dir)
upstream_archive = $(OPK_SOURCE)-$(OPK_SOURCE_VERSION_UPSTREAM).tar.gz
upstream_url = $(upstream_base_url)/$(upstream_archive)
upstream_sum = $(upstream_base_url)/SHA256SUMS.txt
source_archive = ../$(OPK_SOURCE)-$(OPK_SOURCE_VERSION_UPSTREAM).orig.tar.gz

$(source_archive):
	wget -c '$(upstream_url)'
	wget -O - '$(upstream_sum)' | grep -F "$(upstream_archive)" >SHA256SUMS
	sha256sum -c SHA256SUMS
	rm -f SHA256SUMS
	mv '$(upstream_archive)' '$(source_archive)'

source: $(source_archive)