X:Y doesn't include X in svn

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45199 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

tool/merger.rb

@@ -180,6 +180,7 @@ else
     when /\A\d+:\d+\z/
       r = ['-r', rev]
     when /\A(\d+)-(\d+)\z/
+      rev = "#{$1.to_i-1}:#$2"
       r = ['-r', rev]
     when /\A\d+\z/
       r = ['-c', rev]