svn log URL_to_docs | awk '/^r/{gsub(/^r/,"",$1);print $1}' > revisions.txt
#tac for revisions in reverse (oldest revision first)
tac revisions.txt | while read line; do svnadmin dump /svn/old_repo -r$line >> ./docs_revisions.dump ; done
#You don't have to filter if you commited only files in your directory docs in your exported revisions
svndumpfilter include path/to/docs --drop-empty-revs --renumber-revs --preserve-revprops < ./docs_revisions.dump > ./docs_only.dump
svnadmin load /svn/new_repos < ./docs_only.dump