This is a VERY expensive operation as it will read the entire contents of each open source file from disk. Ideally we could change this behavior so that the actual file contents are lazily loaded but this is not a trivial change and carries significant defect risk. Let's discuss possible alternatives -- my inclination is that since the client knows the dirty state of everything if there's a way this part of the calculation could be deferred until we're back on the client that would be ideal.