machinectl import-tar hangs when the import file is multi-streamed

[Jesse Pretorius]

When trying to use machinectl import-tar to import a compressed rootfs tarball, if the compression is multi-streamed then the import hangs after the first stream.

Either the multi-stream import should work, or it should be detected and an error output.

Environment:
Ubuntu 17.10 (Artful Aardvark)
systemd-container 234-2ubuntu12.1

Steps to reproduce:

# install systemd-container
apt-get update && apt-get install systemd-container

# fetch a multi-stream compressed rootfs
wget http://rpc-repo.rackspace.com/lxc-images/ubuntu/xenial/amd64/default-r14.7.0/20180101/rootfs.tar.xz

# verify that it has multiple streams
xz -lvv rootfs.tar.xz

# try to import it
machinectl --verify=no import-tar rootfs.tar.xz test

[Matthew Thode (prometheanfire)]

fixed in https://github.com/systemd/systemd/pull/7857 (tested)