upstream_version = $$(printf '%s\n' '$(OPK_SOURCE_VERSION_UPSTREAM)' | \
	tr '~' '-')
upstream_archive = $(OPK_SOURCE)-$(upstream_version).tar.gz
upstream_url_base = https://download.savannah.gnu.org/releases/$(OPK_SOURCE)
upstream_url = $(upstream_url_base)/$(upstream_archive)
source_archive = ../$(OPK_SOURCE)-$(OPK_SOURCE_VERSION_UPSTREAM).orig.tar.gz

$(source_archive):
	wget -c -O '$(source_archive)' "$(upstream_url)"

source: $(source_archive)