Function basic_packing_with_prior_build 

fn basic_packing_with_prior_build<'a>(
    components: &'a [ObjectSourceMetaSized],
    bin_size: NonZeroU32,
    prior_build: &ImageManifest,
) -> Result<Option<Vec<Vec<&'a ObjectSourceMetaSized>>>>

If the current rpm-ostree commit to be encapsulated is not the one in which packing structure changes, then Flatten out prior_build_metadata to view all the packages in prior build as a single vec Compare the flattened vector to components to see if pkgs added, updated, removed or kept same if pkgs added, then add them to the last bin of prior if pkgs removed, then remove them from the prior[i] iterate through prior[i] and make bins according to the name in nevra of pkgs to update required packages else if pkg structure to be changed || prior build not specified Recompute optimal packaging structure (Compute partitions, place packages and optimize build)

A return value of Ok(None) indicates there was not an error, but the prior packing structure is incompatible in some way with the current build.