I followed this tutorial: http://www.beletsky.net/2011/06/how-to-start-using-git-in-svn-based.html
I did this and it worked fine for a while i could rebase and dcommit and all.
But then I got an error when doing "git svn rebase": "Couldn't find revmap for" It seems that git-svn suddenly thinks that my branch is the svn trunk...
This might be the answer: git-svn import only branch
But I am simply not smart enough to unserstand it.
Edit What I did between the "git svn rebase" that worked and the one giving an error was create a branch and stash a little...
**Edit 2 ** This looks useful as well: git svn clone > git svn rebase > Unable to determine upstream SVN information from working tree history