can't use add-files in treefile with latest rpm-ostree

[cristifalcas]

Host system details
Fedora 28, script is run in a privileged container

Provide the output of rpm-ostree status.
rpm-ostree status
error: This system was not booted via libostree; cannot operate

Expected vs actual behavior
Seems that "rpm-ostree compose tree" tries to go twice over add-files.

.........
Mutating /usr/lib/os.release.d/os-release-atomichost
Adding file 'usr/etc/pki/ca-trust/source/anchors/extra_ca.pem'
Adding file 'usr/etc/ssh/sshd_config'
Adding file 'usr/etc/sudoers'
Adding file 'usr/etc/systemd/system/dev-xvdz.swap'
Adding file 'usr/etc/sysconfig/docker'
Adding file 'usr/etc/sysconfig/docker-network'
Adding file 'usr/etc/sysconfig/docker-storage-setup'
Adding file 'usr/etc/containers/registries.conf'
Adding file 'usr/etc/cloudinit_dbus.te'
Adding file 'usr/etc/sshd_curl.te'
Adding file 'usr/etc/systemd_write_etc.te'
Adding file 'usr/bin/cfssl'
Adding file 'usr/bin/cfssljson'
Adding file 'usr/bin/helm'
Adding file 'usr/etc/systemd/system/kubelet.service.d/20-extra-args.conf'
Adding file 'usr/bin/etcd_readd_member.sh'
Adding file 'usr/etc/profile.d/custom_aliases.sh'
Adding file 'usr/bin/helm_install'
Adding file 'usr/bin/init_docker.sh'
Adding file 'usr/bin/init_instance.sh'
Adding file 'usr/etc/sysctl.d/01-kubernetes.conf'
Adding file 'usr/etc/flannel.te'
Adding file 'usr/etc/certs_dir.te'
Adding file 'usr/etc/pki/ca-trust/source/anchors/extra_ca.pem'
error: Postprocessing: Copying file 'ca/extra_ca.pem' into target: linkat: File exists

Expected:
Should be able to use add-files

Steps to reproduce it

Try to use "rpm-ostree compose tree" version 2018.8-1.fc28 with a treefile that has add-files. This will fail with:

error: Postprocessing: Copying file 'ca/extra_ca.pem' into target: linkat: File exists

Downgrade to 2018.4-1.fc28 and do the same thing again. This time the build is successful.

[jlebon]

OK, just verified that this is fixed in master. It was likely fixed by #1552, before which we parsed the first treefile twice resulting in doubling theadd-files array.