upstream_archive = m4-$(OPK_SOURCE_VERSION_UPSTREAM).tar.bz2
upstream_url = http://ftp.gnu.org/gnu/m4/$(upstream_archive)
source_archive = ../m4-$(OPK_SOURCE_VERSION_UPSTREAM).orig.tar.bz2
keys = 2527436A 2983D606

$(source_archive):
	wget '$(upstream_url)'
	set -e; if gpg --version >/dev/null 2>&1; then \
		wget '$(upstream_url).sig'; \
		[ -e ../keyring.gpg ] || \
			gpg --keyring ../keyring.gpg --no-default-keyring \
				--recv-keys $(keys) || true; \
		gpg --verify --keyring ../keyring.gpg \
			'$(upstream_archive).sig'; \
	fi
	mv '$(upstream_archive)' '$(source_archive)'

source: $(source_archive)