Code review comment for lp:~jameinel/bzr/2.4-transform-cache-sha-740932

Thanks for tackling this.

I wonder if we can take a further step in this direction still within
the current format by just making sure we never actually hash things
from disk: it's enough to just say that they're either identical to
the current tree, or they're unknown. Recording hashes different to
those in any of the basis trees has very little value.

I don't see why we would be recording or checking the stat values of
directories at all. I don't think it can save us any time.

Martin