Make it possible to compare untrusted regexps

lib/gitlab/untrusted_regexp.rb

@@ -9,7 +9,7 @@ module Gitlab
   # there is a strict limit on total execution time. See the RE2 documentation
   # at https://github.com/google/re2/wiki/Syntax for more details.
   class UntrustedRegexp
-    delegate :===, to: :regexp
+    delegate :===, :source, to: :regexp
 
     def initialize(pattern)
       @regexp = RE2::Regexp.new(pattern, log_errors: false)
@@ -31,6 +31,10 @@ module Gitlab
       RE2.Replace(text, regexp, rewrite)
     end
 
+    def ==(other)
+      self.source == other.source
+    end
+
     private
 
     attr_reader :regexp