git-svn and local only topic branch

Hi,

I'm using Git as a SVN frontend (via git-svn). Recently, I made a topic branch, I did some job on it and wish to "upload" my work (on the SVN). But, I do not want "pushing" all commits, I only want to create a single commit on the SVN, while keeping full commits on my Git repo. But I did not find how to do this.

Here my story. Let's call "upstream" the local branch connected to the SVN, the raw SVN mirror branch is remotes/upstream. Now, I create a branch "topic" from "upstream" and I do job:

o--o--o (upstream, remotes/upstream)
         \
          o--o--o--o (topic)

I want the following result:

o--o--o-------------- o (upstream, remotes/upstream)
         \             /
          o--o--o--o (topic)

So I did "git-merge "Merge" upstream topic". But, the merge action decided to do a fast-forward. It's not correct because I really don't want to "pollute" the SVN with all my commits.

So I rewinded and I did "git-merge --squash "Merge" upstream topic". This time, it seems to work as I obtained a single commit on upstream branch. But this commit does not have ancestry link with the topic branch. Here is it:

o--o--o--o (upstream, remotes/upstream)
         \
          o--o--o--o (topic)

Is there a way to do what I want?