Add parenthesis to function def with arguments.

    find . -iname '*.rb' | xargs perl -lapi -e 's/\bdef ([^ (]+)[ ]+([^(].*)/def $1($2)/'
Unused method argument - `tree`. If it's necessary, use `_` or `_tree` as an argument name to indicate that it won't be used. You can also write as `up_dir_path(*)` if you want the method to accept any arguments but don't care about them.