[MERGE] Fix #175520 by implementing a --deep option for log

[Ian Clatworthy]

Robert Collins wrote:
> On Thu, 2009-01-08 at 07:38 +1000, Ian Clatworthy wrote:
>> Hmm, I can see the problem with the above: you can miss
>> references to a file X because the most recent X was once
>> called Y at the same time. Again, not very likely in practice
>> but possible. Fast and correct just aren't going to play
>> together on this task it seems ...
> 
> Looking up a path in split-inventories is much cheaper than in xml
> inventories. Given a node cache and unchanged paths no IO will be
> needed.

Excellent.

> My point - this is a use case supported by the infrastructure in the
> pipeline, so perhaps looking at how it will work there is useful, and
> don't assume we can't do fast and correct :)

My point was better explained by John: we really need to find all
file-ids matching a name and union log those - just looking up
a name across every inventory isn't enough, even if that becomes
faster.

Ian C.