Ruby

Limit uplevel travarsing

• tool/vcs.rb (VCS.detect): limit level of travarsing parent
  directories, 0 by the default. curretly always detecting at the
  source directory itself.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66305 b2dd03c8-39d4-4d8f-98ff-823fe69b080e