VOL-1174: Keep only latest data and apply changes only when committed.

Change-Id: I2311eb9cf1487b39f23066df50d19b47fd5c7dcc
diff --git a/db/model/revision.go b/db/model/revision.go
index 44f97b2..a7b0c39 100644
--- a/db/model/revision.go
+++ b/db/model/revision.go
@@ -19,6 +19,7 @@
 	Finalize()
 	SetConfig(revision *DataRevision)
 	GetConfig() *DataRevision
+	Drop(txid string, includeConfig bool)
 	SetChildren(children map[string][]Revision)
 	GetChildren() map[string][]Revision
 	SetHash(hash string)