Set Bullet Behavior "Strict Subproofs".
Opaque upto.

Lemma data_at_buffer_cohere : forall sh1 sh2 v1 v2 p, readable_share sh1 ->
data_at sh1 tbuffer v1 p * data_at sh2 tbuffer v2 p |--
data_at sh1 tbuffer v1 p * data_at sh2 tbuffer v1 p.