Getting a list of commits between 2 points without upstream changes

[Chris Packham <judge.packham@gmail.com>]

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