git svn clone https://example.com/path/to/trunk -T trunk -b branches -t tags
(may take a long time with large repos, e.g. several days)
Now you can rebase your code! You can do all your work with git - easily branch, stash, rebase, blame, etc. - and when you're done, push back to subversion.
(source)
See subversion branches:
git branch -r
Update the git repo (may take several hours for large repos - you don't need to run this more than once):
git svn fetch --fetch-all
Update the current branch (run this on trunk/master instead of "fetch" above):
git svn rebase
(source)