Now that all merging go through try_acquire_edata_neighbor, the mergeablility checks (including head state checking) are done before reaching the merge hook. In other words, merge hook will never be called if the head state doesn't agree.
Now that all merging go through try_acquire_edata_neighbor, the mergeablility checks (including head state checking) are done before reaching the merge hook. In other words, merge hook will never be called if the head state doesn't agree.