Order in output of "bzr status -S -r"

[Eli Zaretskii]

> Date: Sat, 12 Mar 2011 14:15:43 +0100
> From: John Arbash Meinel <john at arbash-meinel.com>
> CC: bazaar at lists.canonical.com
> 
> I'm guessing the latter shows the status in "iter_changes" or
> "dirblocks" order. I can go into detailed description, but roughly every
> file in a directory is scanned before descending into subdirs. So if you
> have:
> 
>  a
>  b/
>   h/
>    i
>    j
>   k/
>    l
>  m/
>   n
>   o
>  p
> 
> They will come out as:
>  a
>  b
>  m
>  p
>  b/h
>  b/k
>  b/h/i
>  b/h/j
>  b/k/l
>  m/n
>  m/o

But without the -S switch, the order is

 a
 b
 b/h
 b/h/i
 b/h/j
 b/k/l
 b/k
 m
 m/n
 m/o
 p

I.e., in depth-first search order.  Why does -S change the order?