hudson.Util.useNativeChmodAndMode to true.
JENKINS-36088, Jenkins features controlled by system properties
hudson.lifecycle.ExitLifecycle to exit instead of restart.
JENKINS-47043, Jenkins features controlled by system properties
jenkins.war command-line arguments via standard input using the --paramsFromStdIn parameter.
pull 3223, documentation
Jenkins#getInstance() is now deprecated as its semantics have been a source of confusion for some time. Use #get() in typical cases and Jenkins#getInstanceOrNull() in rare cases (see Javadoc).
JENKINS-48638
User#getUser(String) in favor of the User#getById() or the new User#getOrCreateByIdOrFullName() methods.
JENKINS-47718
SecurityListener.
JENKINS-27027
hudson.util.Service in favor of Java's ServiceLoader.
pull 3191
winstone-*.jar in the temp folder from using up disk space needlessly.
JENKINS-22088