This simplifies remapping task, since you don't have to ensure your
overrides are created in the correct dependency order.
Uses famous LIB_TAG_DOIT to mark IDs to be overridden.
Code also handling auto-generation of static overrides.
Aside from some naming consistency cleanup, this commit:
* Is the first step addressing the 'operator' issue with static
overrides, by implementing a first version of the 'restore from
reference' behavior.
* Fixes several issues that were discovered on the way in enhanced
RNA comparision code, like the 'zero-length dynamic array' case, or some
infinite looping caused by some non-ID pointers (that for some
mysterious reasons did not show up previously...).
* Factorizes a bit said RNA comparison code (auto-static override
generation and comparison/check were essentially doing the same thing).
When one creates a new local static override from another linked
data-block already overriding a third one etc., walk the whole
inheritance chain up to the original ancestor to try to find an
overriding template, instead of only checking the immediate reference...
This is essentially a huge refactor/extension of our existing RNA
compare & copy code, since static override needs more advanced handling here.
Note that not all new features are implemented yet, advanced things like
collections insertion/deletion are still TODO (medium priority).
This completes the ground work for overrides, remaining commits will be
about UI and some basic/testing activation of overrides for a limited
set of data-blocks & properties.
For details see https://developer.blender.org/D2417
See https://developer.blender.org/D2417 for details.
Note that since static overrides rely heavily on RNA, this commit is
essentially invisible from user PoV, more in next commits.
