dbca1afefa
This is similar to some other datablocks. Mainly applies to collections, so freeing scene does not involve changing any non-directly owned data. There are two main usecases foreseen for the future: - Less CPU ticks on bmain free, where everything is freed anyway and there is no need to preserve id counters. - Easier freeing of temporary data, including data which is used by depsgraph's copy-on-write mechanism. Neither of those are currently implemented, but will be shortly.