Getting a list of commits between 2 points without upstream changes

Hi List,

I'm trying to send round an incremental changelog for my project which
contains just my changes without changes that have been made upstream.
The history look something like this.

---o--o--o--o--o--o--o--o-- upstream
    \          \        \
     \-m--A--m--B--m--C--D-- topic

What I want is a changelog with just B, C and D in it (i.e. no merge
commits and no commits already in upstream). I know if I wanted A,B,C
and D I could just do 'git log --no-merges upstream..topic'. If I do
'git log --no-merges B..topic' I get the merged commits from upstream.
In set-speak what I think want is the union of upstream..topic and
B..topic.

Is there any existing way to achieve this? I'm happy to hack something
up using git rev-list if necessary.

Thanks,
Chris