Based on further conversation with the Artifactory plugin developers, revisiting this extension point.

This is a breaking change, but this extension point was added very recently, and it's based on the input from Artifactory plugin, so there's not much point in keeping one that doesn't serve the intended use case.

IMO this needs further refactoring - respect separation of concerns:
it's not AbstractProject's call to trigger a node offline

Added Queue.schedule2 to allow the caller to retrieve the existing item in the queue. AbstractProject.doBuild() changed the behavior a bit to reply 201 if the item was already found in the queue (instead of a new one created.)

"201 Created" response doesn't work well with a browser as the user agent.

Fix ListJobsCommandTest failed on Windows by replace line ending

... although the primary use case still is. Suggested by Kutzi.

This page gets displayed when we throw an unhandled exception.

The exception handler ended up adding almost all the headers again,
resulting in a lot of duplicate headers.

Most critically, stapler was adding "Content-Encoding" header twice,
breaking browsers.

Add documentation about it. ref. [JENKINS-18451]

If someone knows a way to display this help section only for Maven jobs, feel
free to amend this commit.

use more explicit method name
use formattedDescription for all parameter types

This version supports piping of stdout/stderr directly into
OutputStream, avoiding the need for running a thread to pump the stream.

Integrated the new version of remoting

Not recording in the changelog as the regression isn't released yet.

Fire the "jenkins:apply" event from the apply button and listen to that to write back edits to <TEXTAREA>

Verified that JENKINS-5076 is no longer happening.

Looking at the code, I think the actual fix was in a2d82576.

Exposed the UI that sets the assigned label of matrix projects.
This deprecates the "Matrix tie parent" plugin.

Reimplemented a proper topological sort and generates a total order
comparison function.

FingerprintCleanupThread can now partially clean up a fingerprint record
by removing portions of it that's not referencing existing stuff.

[FIXED JENKINS-17713] JobColumn/column.jelly needs to have an itemGroup for display name calculation.
So passing it in explicitly from both the view main page and from the Maven module set modules page.
A more automatic solution might be to make getRelativeDisplayNameFrom use Ancestor.

Added a listener that gets called at the end of the test to provide opportunity for a cleanup.
This avoids the code duplication between HudsonTestCase vs JenkinsRule, too.

(cherry picked from commit 9c4cb4b5eca4fbeba5730b66f52042f647075ff8)