UPSTREAM_VER = $$(printf '%s\n' '$(OPK_SOURCE_VERSION_UPSTREAM)' | \
	sed 's/^\([0-9a-z.~-][0-9a-z.~-]*\)+sip[1-9][0-9]*.*$$/\1/')
UPSTREAM_URL = http://zlib.net/zlib-$(UPSTREAM_VER).tar.gz
SOURCE_ARCHIVE = ../zlib-$(OPK_SOURCE_VERSION_UPSTREAM).orig.tar.bz2

$(SOURCE_ARCHIVE):
	wget -O - "$(UPSTREAM_URL)" | tar -xz
	rm -f "zlib-$(UPSTREAM_VER)"/doc/rfc*.txt
	tar -cjf '$(SOURCE_ARCHIVE)' "zlib-$(UPSTREAM_VER)"
	rm -Rf src
	mv "zlib-$(UPSTREAM_VER)" src

source: $(SOURCE_ARCHIVE)