Phosphor code updater

[Lei YU]

>     By default, image-rwfs is an empty image with size 0, and thus it will NOT be
>     updated to rwfs partition. So by default rwfs is preserved during code update.
> Then how will we get a clean install. If we want to have complete factory reset with empty rw.

This could be done by doing a [factory reset][1].
Example REST API:
curl ... -X POST -d '{"data": []}'
https://$bmc/xyz/openbmc_project/software/action/Reset


> Also how can we add machine name to manifest file which can be used to verify if the image is being built for same target.

This is good suggest and not implemented, welcome to add this feature!

[1]: https://github.com/openbmc/phosphor-dbus-interfaces/tree/05375b14e5a68ac249da6a8cd68e3d522a7ed022/xyz/openbmc_project/Common/FactoryReset