There is

svn revert -R

But sometimes after a svn merge, I see a lot of files are marked as modified because their property has changed. There is a way of reverting them separately.

Reverting all file changes

svn st | grep -e '^M' | awk '{print $2}' | xargs svn revert

Revert all file property changes

svn st | grep -e '^\sM' | awk '{print $2}' | xargs svn revert