This adds a new `org.osbuild.bind` mount feature to the osbuild
mount modules. This allows to (r)bind mount parts of another mount
into the tree (or replace the default tree for a stage entirely).
The use case is the `bootc install to-filesystem` where we get
a populated disk and need to do customizations directly there
without going through an intermediate tree.
Note that right now only "--rbind" is supported and used but
we could trivially change that to become an option in either
direction. Given that the main use-case right now is to be
paried with `org.osbuild.ostree.deployment` and here the
`rbind` is crucial I would leave that the default.
Here is an example what this looks like:
```json
{
"type": "org.osbuild.users",
"options": {
"users": {
"alice": {
"home": "/home/alice",
"groups": [
"wheel"
],
"password": "$6$NV3P7UzUqP3xb1ML$3qnHpWs037VRTaOc.kirQ4.RwNz4gu9dkhAhpBYVCkHw8CMhpBKnegyyqw0QfURowarZnRnQi.jo4JEzIOvPO/",
"key": "ssh-rsa AAA ... user@email.com"
}
}
},
"devices": {
"disk": {
"type": "org.osbuild.loopback",
"options": {
"filename": "disk.raw",
"partscan": true
}
}
},
"mounts": [
{
"name": "part4",
"type": "org.osbuild.ext4",
"source": "disk",
"target": "/",
"partition": 4
},
...
{
"name": "ostree.deployment",
"type": "org.osbuild.ostree.deployment",
"options": {
"source": "mount",
"deployment": {
"default": true
}
}
},
{
"name": "bind",
"type": "org.osbuild.bind",
"target": "tree://",
"options": {
"source": "mount://"
}
}
]
},
```
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