In COSA when we create a disk image we stamp in a .coreos-aleph-version.json file that we then use for various other things later in time. We need an equivalent component when building disk images using OSBuild. Today the file is creating using this code:

cat > $rootfs/.coreos-aleph-version.json << EOF
{
    "build": "${buildid}",
    "ref": "${ref}",
    "ostree-commit": "${commit}",
    "imgid": "${imgid}"
}
EOF

We can feed some of this information into OSBuild via the manifest file but it might be really nice to be able to detect it dynamically from the installed tree so that we can reduce the requirements on future users of this having to know the values.

Another thing, I think since the `imgid` part here depends on what kind of image we are creating I think we might need to create a separate pipeline (i.e. `tree-qemu`) that adds in the correct imgid part, that is then fed into the qcow2 assembler. We probably also need to do something similar for `ignition.platform.id=qemu` in the future.

GitHub Internal PR: https://github.com/dustymabe/osbuild/pull/10
Upstream PR to OSBuild: https://github.com/osbuild/osbuild/pull/1475