BundlePostInstall hook's rsync command needs a slash

[ChrisPbb]

Kairos version:

kairos@localhost:~$ cat /etc/os-release
PRETTY_NAME="Ubuntu 22.04.5 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.5 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=jammy
kairos@localhost:~$ cat /etc/kairos-release
KAIROS_BUG_REPORT_URL="https://github.com/kairos-io/kairos/issues"
KAIROS_HOME_URL="https://github.com/kairos-io/kairos"
KAIROS_SOFTWARE_VERSION_PREFIX="k3s"
KAIROS_ID="kairos"
KAIROS_FLAVOR="ubuntu"
KAIROS_RELEASE="v3.2.3"
KAIROS_ARTIFACT="kairos-ubuntu-22.04-core-amd64-generic-v3.2.3"
KAIROS_TARGETARCH="amd64"
KAIROS_VARIANT="core"
KAIROS_GITHUB_REPO="kairos-io/kairos"
KAIROS_NAME="kairos-core-ubuntu-22.04"
KAIROS_ID_LIKE="kairos-core-ubuntu-22.04"
KAIROS_IMAGE_REPO="quay.io/kairos/ubuntu:22.04-core-amd64-generic-v3.2.3"
KAIROS_IMAGE_LABEL="22.04-core-amd64-generic-v3.2.3"
KAIROS_FLAVOR_RELEASE="22.04"
KAIROS_FAMILY="ubuntu"
KAIROS_MODEL="generic"
KAIROS_REGISTRY_AND_ORG="quay.io/kairos"
KAIROS_VERSION="v3.2.3"
KAIROS_VERSION_ID="v3.2.3"
KAIROS_PRETTY_NAME="kairos-core-ubuntu-22.04 v3.2.3"
kairos@localhost:~$

CPU architecture, OS, and Version:

kairos@localhost:~$ uname -a
Linux localhost 6.8.0-48-generic #48~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Mon Oct  7 11:24:13 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

Describe the bug
The source image's extensions are not properly copied over to the machine after install. Instead they all end up in /var/lib/extensions/extensions, causing systemd-sysext to treat them all as one big extension.

According to the rsync man page:

A trailing slash on the source ... [avoids] creating an additional directory level at the destination.

Thus, I think the culprit is the BundlePostInstall hook's rsync command. We should be able to solve the issue with a / on the source (example below)

cmd := exec.Command("rsync", "-aqAX", "/var/lib/extensions/", "/usr/local/.state/var-lib-extensions.bind")

To Reproduce
Define some bundles under install.bundles and provision a system. Notice the resulting system has /var/lib/extensions/extensions.

Expected behavior
The source image's /var/lib/extensions content is copied to the bind mount instead of the entire extensions directory itself.

Logs

kairos@localhost:~$ ls -l /var/lib/extensions/
total 8
d--------- 2 root root 4096 Dec 27 20:55 extensions
drwxr-xr-x 4 root root 4096 Dec 27 20:57 <CENSORED>
kairos@localhost:~$