svnlook tree --full-paths "$REPO" | grep '/branches/[^/]*/$' | \
while read branch ; do
svnlook history -l 1 "$REPO" "$branch"
done | while read revision path ; do
# Input looks like the following, in a loop...
#
# REVISION PATH
# -------- ----
# 20 /path/to/branch
case "$revision" in
REVISION|--------) : ;; # Skip headers
*) echo "$path" 'svnlook date -r "$revision" "$REPO"'
;;
esac
done