bzr log --short; merging into an empty branch

[Tom Tobin]

I've found myself with the following workflow in certain cases:

1) Making a branch of an upstream project with a particular
overarching goal in mind
2) Making minor "feature" branches from that branch as I work and
merging them back in

I like how I can use use "bzr log --short" on that local main branch
to see only the merge messages from my feature branches; I *don't*
like how the history from the original project also gets included.
Trying to get around this, I've tried starting out by merging the
upstream project into an empty branch, only to discover that you can't
do that.  ^_^  Is there another way to get "bzr log" to leave off the
original history in a branch, or to merge into an empty branch?