contrib/rootfs-builder: Support xz (and other) compression formats

I'm not sure when the change happened (sometime since ff5e578,
contrib/rootfs-builder: Support multiple architectures, 2017-09-20,
#479), but Gentoo is now using xz compression for some amd64 stages:

  $ curl http://distfiles.gentoo.org/releases/amd64/autobuilds/latest-stage3.txt
  # Latest as of Fri, 09 Mar 2018 15:00:02 +0000
  # ts=1520607602
  20180308T214502Z/stage3-amd64-20180308T214502Z.tar.xz 188851072
  20180308T214502Z/hardened/stage3-amd64-hardened-20180308T214502Z.tar.xz 174759140
  20180308T214502Z/hardened/stage3-amd64-hardened+nomultilib-20180308T214502Z.tar.xz 167639136
  20180301T214503Z/hardened/stage3-amd64-hardened-selinux-20180301T214503Z.tar.xz 187319664
  20180308T214502Z/stage3-amd64-nomultilib-20180308T214502Z.tar.xz 181866296
  20180303/systemd/stage3-amd64-systemd-20180303.tar.bz2 281873162
  20180225/uclibc/stage3-amd64-uclibc-hardened-20180225.tar.bz2 57147392
  20180225/uclibc/stage3-amd64-uclibc-vanilla-20180225.tar.bz2 144490332
  20180308T214502Z/stage3-x32-20180308T214502Z.tar.xz 205285160
  20180308T214502Z/hardened/stage4-amd64-hardened+minimal-20180308T214502Z.tar.bz2 261776436
  20180308T214502Z/hardened/stage4-amd64-hardened+minimal-nomultilib-20180308T214502Z.tar.bz2 251821245
  20180308T214502Z/stage4-amd64-minimal-20180308T214502Z.tar.bz2 280918565
  20180308T214502Z/stage4-amd64-minimal-nomultilib-20180308T214502Z.tar.bz2 268835860
  20180303/systemd/stage4-amd64-systemd-20180303.tar.bz2 622067712

This commit adapts to that change, allowing us to continue to pull the
vanilla stage3-amd64-20180308T214502Z.tar.xz.

Signed-off-by: W. Trevor King <wking@tremily.us>

Author: wking

contrib/rootfs-builder/Makefile

@@ -6,15 +6,15 @@ rootfs-%.tar.gz: rootfs/%/bin/echo
 	tar -czf $@ -C rootfs/$* .
 
 .PRECIOUS: rootfs/%/bin/busybox
-rootfs/%/bin/busybox: downloads/stage3-%-current.tar.bz2 rootfs-files
+rootfs/%/bin/busybox: downloads/stage3-%-current.tar rootfs-files
 	gpg --verify $<.DIGESTS.asc
 	(cd downloads && \
-		grep -A1 '^# SHA512 HASH' stage3-$*-current.tar.bz2.DIGESTS.asc | \
+		grep -A1 '^# SHA512 HASH' stage3-$*-current.tar.DIGESTS.asc | \
 		grep -v '^--' | \
 		sha512sum -c)
 	sudo rm -rf rootfs/$*
 	sudo mkdir -p rootfs/$*
-	sudo tar -xvf downloads/stage3-$*-current.tar.bz2 -C rootfs/$* \
+	sudo tar -xvf downloads/stage3-$*-current.tar -C rootfs/$* \
 		--no-recursion --wildcards $$(< rootfs-files)
 	sudo touch $@
 
@@ -24,9 +24,9 @@ rootfs/%/bin/echo: rootfs/%/bin/busybox
 		test -L "rootfs/$*/bin/$${COMMAND}" || ln -rs $< "rootfs/$*/bin/$${COMMAND}" || exit; \
 	done'
 
-downloads/stage3-%-current.tar.bz2: get-stage3.sh
+downloads/stage3-%-current.tar: get-stage3.sh
 	STAGE3_ARCH=$* ./$<
-	touch downloads/stage3-$*-*.tar.bz2
+	touch downloads/stage3-$*-*.tar
 
 clean:
 	rm -f downloads/*

contrib/rootfs-builder/get-stage3.sh

@@ -78,13 +78,23 @@ then
 			die "could not calculate DATE from ${BASE_ARCH_URL}latest-stage3.txt"
 		fi
 	fi
-	STAGE3="${STAGE3:-stage3-${STAGE3_ARCH}-${DATE}.tar.bz2}"
+
+	STAGE3=$(echo "${LATEST}" | sed -n "s|${DATE}/\(stage3-${STAGE3_ARCH}-${DATE}[.]tar[.][^ ]*\) .*|\1|p")
+	if test -z "${STAGE3}"
+	then
+		die "could not calculate STAGE3 from ${BASE_ARCH_URL}latest-stage3.txt"
+	fi
 fi
 
 ARCH_URL="${ARCH_URL:-${BASE_ARCH_URL}${DATE}/}"
 STAGE3_CONTENTS="${STAGE3_CONTENTS:-${STAGE3}.CONTENTS}"
 STAGE3_DIGESTS="${STAGE3_DIGESTS:-${STAGE3}.DIGESTS.asc}"
 
+COMPRESSION=$(echo "${STAGE3}" | sed -n 's/^.*[.]\([^.]*\)$/\1/p')
+if test -z "${COMPRESSION}"
+then
+	die "could not calculate COMPRESSION from ${STAGE3}"
+fi
 for FILE in "${STAGE3}" "${STAGE3_CONTENTS}" "${STAGE3_DIGESTS}"; do
 	if [ ! -f "downloads/${FILE}" ]; then
 		wget -O "downloads/${FILE}" "${ARCH_URL}${FILE}"
@@ -94,12 +104,15 @@ for FILE in "${STAGE3}" "${STAGE3_CONTENTS}" "${STAGE3_DIGESTS}"; do
 		fi
 	fi
 
-	CURRENT=$(echo "${FILE}" | sed "s/${DATE}/current/")
+	FILE_NOCOMPRESSION=$(echo "${FILE}" | sed "s/[.]${COMPRESSION}//")
+	if [ "${FILE_NOCOMPRESSION}" = "${FILE}" ]; then
+		die "unable to remove .${COMPRESSION} from ${FILE}"
+	fi
+	CURRENT=$(echo "${FILE_NOCOMPRESSION}" | sed "s/${DATE}/current/")
 	(
 		cd downloads &&
 		rm -f "${CURRENT}" &&
 		ln -s "${FILE}" "${CURRENT}" ||
 		die "failed to link ${CURRENT} -> ${FILE}"
 	)
 done
-