tool/redmine-backporter.rb: scroll 1 lind on Enter key

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45188 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
tool/merger.rb: normalize the merged revision string

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45189 b2dd03c8-39d4-4d8f-98ff-823fe69b080e