I'm looking for an efficient way to get the list of unique commit authors for an SVN repository as a whole, or for a given resource path. I haven't been able to find an SVN command specifically for this (and don't expect one) but I'm hoping there may be a better way that what I've tried so far in Terminal (on OS X):

svn log --quiet | grep "^r" | awk '{print $3}'

svn log --quiet --xml | grep author | sed -E "s:</?author>::g"

Either of these will give me one author name per line, but they both require filtering out a fair amount of extra information. They also don't handle duplicates of the same author name, so for lots of commits by few authors, there's tons of redundancy flowing over the wire. More often than not I just want to see the unique author usernames. (It actually might be handy to infer the commit count for each author on occasion, but even in these cases it would be better if the aggregated data were sent across instead.)

I'm generally working with client-only access, so svnadmin commands are less useful, but if necessary, I might be able to ask a special favor of the repository admin if strictly necessary or much more efficient. The repositories I'm working with have tens of thousands of commits and many active users, and I don't want to inconvenience anyone.