upstream_archive = $(OPK_SOURCE)-$(OPK_SOURCE_VERSION_UPSTREAM).tar.gz
upstream_url = https://www.joonet.de/lilo/ftp/sources/$(upstream_archive)
source_archive = ../$(OPK_SOURCE)-$(OPK_SOURCE_VERSION_UPSTREAM).orig.tar.gz

gpg = GNUPGHOME=gnupghome/ gpg --no-default-keyring --keyring ../keyring.gpg
keys = \
	'5E78 7F8D B58F 02AF 5C63  C9DD 4A22 5464 1FE1 B08B' \
	'46A6 2D7D 44A2 6FBE 10D7  EEE7 3139 3680 39A1 1092'

$(source_archive):
	wget -c '$(upstream_url)' '$(upstream_url).asc'
	install -m 0700 -d gnupghome/
	[ -e ../keyring.gpg ] || \
		$(gpg) --keyserver hkp://pool.sks-keyservers.net \
			--recv-keys $(keys); \
	rm -f ../keyring.gpg~; \
	if ! $(gpg) --verify '$(upstream_archive).asc'; then \
		rm -Rf gnupghome/; \
		exit 1; \
	fi
	rm -Rf gnupghome/
	mv '$(upstream_archive)' '$(source_archive)'

source: $(source_archive)