Comment 6 for bug 806348

I should note that another aspect here is that so far it appears that this situation only occurs when fetching multiple heads (as now commonly happens because we fetch missing tags in recent bzr versions). I'm not certain that fetching one head at a time can't hit a similar problem, but if that is safe it suggests that perhaps a fix could be:
 * when calculating which records to stream do so independently for each head and then send the union of those streams.

That feels too expensive to me though (both in computation effort, and in possibly sending redundant data).