vcs.rb: fix r61054
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61056 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
vcs.rb: fix r61054
whole arguments for IO.popen as the second argument, that is an
array of command and mode.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61056 b2dd03c8-39d4-4d8f-98ff-823fe69b080e