Those are bugs which might require some technical knowledge but no deep
dive knowledge of the entire code. So, take ownership of one, and just
work on it. If you see that you need help, ask us, we're more than happy
to help. If you recognize that you can't progress anymore, be honest and
tell us, we'll understand (we also have sometimes a private life).
The issue #51 is special in this regard that multiple persons can work
on it, and you don't need any Python knowledge: we would need volunteers
to go through the Savannah bugs, try to reproduce them on version 2.x of
rdiff-backup and create a "mirror" issue in GitHub if they are still
valid. Add to it the simplest possible procedure (like a shell script)
on how to reproduce the bug (or clarify the enhancement request). Make
sure that you link both old and new bugs together in comments (or state
that you can't reproduce it or it's a duplicate), and take ownership of
a Savannah bug _before you start_ by adding a comment.
(the instructions are also documented in #51c591286234)