check the existence of specified tag
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61267 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
check the existence of specified tag
get rid of careless mistakes.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61267 b2dd03c8-39d4-4d8f-98ff-823fe69b080e