The official documentation describes the format of packfiles to include 6 types of objects, i.e. Commit, Blob, Tree, Tag, OffsetDelta and RefDelta. OffsetDelta is clearly described as being defined in context of an object (which itself can be a delta) earlier in the pack. However, RefDelta can be defined in context of any object based solely on the ObjectId.
The documentation mentions that RefDeltas are typically used to delta against objects outside the pack (so called thin-packs) but can they be used to delta against objects in the same pack? I am manually generating packfiles so I am curious to know the standard practice with respect to packfile format.