I am in the process of migrating (to git) some debian packages from a subversion repository created with svn-inject -l 2, namely

/trunk/package 
/branches/upstream/package/ 
/tags/package

Here is a script I wrote that seems to do the trick

#!/bin/sh

package=$1
stage=$1.from-svn
set -x
# my debian packages live under $SVNROOT/debian, with layout 2
mkdir $stage
cd $stage
git-svn init --no-metadata \
    --trunk $SVNROOT/debian/trunk/$package \
    --branches $SVNROOT/debian/branches/upstream/$package \
    --tags $SVNROOT/debian/tags/$package 
git-svn fetch 
git branch -r upstream current
 cd ..
# git clone --bare loses some gunk from git-svn. Anyway we need a bare repo
git clone --bare $stage $1.git

rm -rf $stage

Your mileage may vary of course.

UPDATED Apparently 'git branch -r upstream current' no longer works, if it ever did. If anyone can psychically figure out what I wanted to do there, I'm happy to translate that into git.