Code review comment for lp:~abentley/bzr/skip-dupes

Thank you for making these changes. I was still nervous about things
going wrong - stepping back from paranoia isn't easy.

If you can do the following, I'll feel comfortable that things won't go
badly wrong *and* get ignored by users.

Add some sort of flag to the state of the GroupCompressVersionedFiles
object indicating 'trace or raise'. Then in the GCPackRepository
__init__, set the flag as follows:
revisions: raise
inventories: trace
texts: trace
signatures: trace
chk_bytes: trace

This will mean that if the revisions graph is wrong we stop cold - which
is important because that affects fetch. The other graphs don't affect
fetch and are consequently a lower priorityIMO.

-Rob