Dup string to avoid future frozen value from symbols

Author: JonRowe

lib/rspec/core/drb.rb

@@ -91,7 +91,7 @@ def add_full_description(argv)
       def add_filter(argv, name, hash)
         hash.each_pair do |k, v|
           next if CONDITIONAL_FILTERS.include?(k)
-          tag = name == :inclusion ? k.to_s : "~#{k}".dup
+          tag = name == :inclusion ? k.to_s.dup : "~#{k}".dup
           tag << ":#{v}" if v.is_a?(String)
           argv << "--tag" << tag
         end unless hash.empty?