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: http://bugs.java.com/bugdatabase/view_bug.do?bug_id=8051847
Reference: ZD-23093

Reference: ZD-23093

Caused a failure in hudson.plugins.promoted_builds.conditions.ManualConditionTest.testManualPromotionProcessViaWebClient when run against 1.580.1.

Explode WAR fails when ./target does not yet exist (e.g., run from IDEA)

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

Create parent directory before trying to lock dir using files.

java.lang.Exception: Failed to initialize exploded war
at org.jvnet.hudson.test.WarExploder.getExplodedDir(WarExploder.java:49)
at org.jvnet.hudson.test.JenkinsRule.createWebServer(JenkinsRule.java:582)
at org.jvnet.hudson.test.JenkinsRule.newHudson(JenkinsRule.java:538)
at org.jvnet.hudson.test.JenkinsRule.before(JenkinsRule.java:332)
at org.jvnet.hudson.test.JenkinsRule$2.evaluate(JenkinsRule.java:482)
at org.junit.rules.ExternalResource$1.evaluate(ExternalResource.java:48)
at org.junit.rules.RunRules.evaluate(RunRules.java:20)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.junit.runner.JUnitCore.run(JUnitCore.java:160)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:74)
at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:211)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:67)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: java.io.FileNotFoundException: /Users/integer/Documents/idea/jenkins-ws-git-plugin/./target/jenkins-for-test.exploding (No such file or directory)
at java.io.FileOutputStream.open(Native Method)
at java.io.FileOutputStream.(FileOutputStream.java:212)
at java.io.FileOutputStream.(FileOutputStream.java:104)
at org.jvnet.hudson.test.WarExploder.explode(WarExploder.java:99)
at org.jvnet.hudson.test.WarExploder.(WarExploder.java:58)
... 24 more

Update ChoiceParameterDefinition

The "it.value" don't exist, so we need to set the defaultParameterValue. 

It help me display correctly parameter for my multilauncher plugin. 
Note that other ParameterDefinition use the default value to display parameter, so IMO it is safe to do this.

Better debug messages in JSONSignatureValidator

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 …