For Travis CI - (test successive commits do not cause build error).

Rakefile

@@ -281,8 +281,7 @@ end
 desc 'Delete CI mirror branch'
 task :ci_delete_mirror do
   # Skip if there are more commits since this one
-  last_commit = `git fetch origin; git log -1 --pretty=format:"%H" origin/master`
-  if last_commit == ENV['TRAVIS_COMMIT']
+  if `git fetch origin; git log -1 --pretty=format:"%H" origin/master` == ENV['TRAVIS_COMMIT']
     system 'git config user.name $GIT_NAME && git config user.email $GIT_EMAIL && git remote set-url --push origin https://[email protected]/$TRAVIS_REPO_SLUG.git'
     system "git push -qf origin --delete #{ENV['TRAVIS_BRANCH']}" or abort "Failed to delete #{ENV['TRAVIS_BRANCH']} mirror branch"
   end