[merge-tracking] 'svn blame' auditing

In response to my query in irc a few days ago, Dan Rall mentioned that
there are a few aspects of merge tracking that can be worked on in
parallel to the work that is currently being done. One of those items
is auditing[1].

I've decided to investigate what needs to be done to implement 'svn
blame' auditing support. For those unfamiliar with the problem, the use
case is simple. Quoting [1]: "If you merge rN into a branch B, and rN
was committed by author A, then svn blame should show the changed lines
in B as last touched by A, even if the merge was committed by you and
you are not A. This must also work when merging a range of revisions
with different authors."

Before I begin, though. I would like to know if
a) Anybody else is currently working on this.
b) Anybody has any suggestions/recommendations as to where to begin.

If all goes well, I hope to be able to start posting patches in the next
couple of weeks.

Thanks,
-Hyrum

[1] http://subversion.tigris.org/merge-tracking/requirements.html#auditing