fn planned_root_size_mib(planned: &[RepartPartition]) -> Result<NonZeroU64>Expand description
The size in MiB to pin the root partition we generate to, given a dry run of all definitions in which it has no size limits. systemd-repart gives it the space the other definitions leave, padding included, and shares that by Weight= with any of them that can grow, so the partitions created only on first boot still fit after it. Rounded down to whole MiB.