#1406 silently skipped the call to moveDirectory in case newBuildDir.isDirectory(), rather than throwing an IOE as renameTo does.
Also deleting apparently useless call to forceMkdir.

Tested on a windows box to automaticaly install 1.4, 1.5, 1.6, 1.7 and 1.8 JDKs

[FIXED JENKINS-23797] Produce human readable output in DiskSpaceMonitorDescriptor.DiskSpace.toString()

Not fully solved, since the scannedDirs field can still grow to be large, but at least clearing files/dirsNotIncluded.
Also imposing a 5s timeout on the scan regardless of file count, and defining a user-customizable bound.

[JENKINS-25691] Might have prevented the need for: https://github.com/jenkinsci/maven-plugin/pull/33

ssh-slaves plugin can leverage this to try to obtain the state of the slave JVM via SSH.

Reference: ZD-23093

Reference: ZD-23093

Allow Projects to take the Queue.Item's actions into consideration when determining their default authentication

- Also tidy up some holes in locking strategy that can cause builds to be scheduled on
  executors that are about to be interrupted or nodes in the process of being removed

AtomicFileWriter.commit should use Util.deleteFile so as to get a more meaningful error message in case the deletion fails.
The following is not helpful in terms of diagnosing the root problem:
java.io.IOException: Unable to delete /…/jobs/demo/builds/…/workflow/3.xml
	at hudson.util.AtomicFileWriter.commit(AtomicFileWriter.java:112)
	at hudson.XmlFile.write(XmlFile.java:179)
	at org.jenkinsci.plugins.workflow.support.storage.SimpleXStreamFlowNodeStorage.saveActions(SimpleXStreamFlowNodeStorage.java:106)
	at …

jenkins.model.Jenkins::getInstance() method is marked as @CheckForNull, but the most of Jenkins code does not actually check the return value. It leads to tons of static analysis errors, hence it is hard to analyze the code.

The change also adds annotations to old methods like Hudson::getInstance()
Signed-off-by: NOleg Nenashev <o.v.nenashev@gmail.com>

[JENKINS-2786] Makes no sense for Computer.currentComputer to return MasterComputer when not on an executor thread.

Even though SezpozModule.configure catches and ignores the faulty component, Guice still dies:
… hudson.ExtensionFinder$GuiceFinder <init>
SEVERE: Failed to create Guice container from all the plugins
com.google.inject.internal.guava.collect.$ComputationException: java.lang.NoClassDefFoundError: org/eclipse/jgit/storage/file/FileRepository
	at …
	at com.google.inject.Guice.createInjector(Guice.java:73)
	at hudson.ExtensionFinder$GuiceFinder.<init>(ExtensionFinder.java:279)

[FIXED JENKINS-25400] Rework fix of JENKINS-22769 (c04cdcd9) to put the burden on each listener to impersonate ACL.SYSTEM if it needs to.

Signed-off-by: NOleg Nenashev <o.v.nenashev@gmail.com>

Resource leak may happen during the search of manifest file.
Signed-off-by: NOleg Nenashev <o.v.nenashev@gmail.com>

The issue is related to JENKINS-18351.
Signed-off-by: NOleg Nenashev <o.v.nenashev@gmail.com>

Signed-off-by: NOleg Nenashev <o.v.nenashev@gmail.com>