Recently at work I had to checkout a repository that I was previously syncing to an SVN repo. It turns out the SVN history is kept in the commits so I just needed a way to convince git-svn that the current master branch was in fact linked to the SVN repo’s head.
[svn-remote "svn"]
url = http://host/svn/base
fetch = path/to/trunk:refs/remotes/trunk
First I had to add the above snippet to my .git/config file in the repo. This
tells git-svn where to pull from. Next I told it what trunk currently was by
placing the sha hash of the current master branch into the svn trunk ref:
cat .git/refs/heads/master > .git/refs/remotes/trunk
At this point just running git svn fetch works again and git-svn has been
happily working since!