brew search can take a --desc argument to search descriptions

Library/Homebrew/cmd/search.rb

@@ -20,6 +20,13 @@ module Homebrew
       exec_browser "https://admin.fedoraproject.org/pkgdb/packages/%2A#{ARGV.next}%2A/"
     elsif ARGV.include? '--ubuntu'
       exec_browser "http://packages.ubuntu.com/search?keywords=#{ARGV.next}&searchon=names&suite=all&section=all"
+    elsif ARGV.include? '--desc'
+      query = ARGV.next
+      Formula.each do |formula|
+        if formula.desc =~ query_regexp(query)
+          puts "#{formula.name}: #{formula.desc}"
+        end
+      end
     elsif ARGV.empty?
       puts_columns Formula.names
     elsif ARGV.first =~ HOMEBREW_TAP_FORMULA_REGEX