scm: mercurial: add "summary" method in adapter (#4455).

Contributed by Yuya Nishihara.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4845 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine/scm/adapters/mercurial_adapter.rb

@@ -93,6 +93,13 @@ module Redmine
           return nil
         end
 
+        def summary
+          @summary ||= hg 'rhsummary' do |io|
+            ActiveSupport::XmlMini.parse(io.read)['rhsummary']
+          end
+        end
+        private :summary
+
         def entries(path=nil, identifier=nil)
           path ||= ''
           entries = Entries.new