Merge pull request #4331 from tsparber/patch-1

Add note to run mvn hudson-dev:run to CONTRIBUTING.md

Author: oleg-nenashev

CONTRIBUTING.md

@@ -39,6 +39,17 @@ If you want to debug this WAR file without using Maven plugins,
 You can just start the executable with [Remote Debug Flags]
 and then attach IDE Debugger to it.
 
+To compile and launch a development instance, run:
+
+    mvn hudson-dev:run
+
+<!--
+This should be `mvn hudson-dev:run` as long as JENKINS-23364 is not resolved.
+For jenkis-dev:run it is currently necessary to add `org.jenkins-ci.tools` as a plugin group
+to the maven settings.xml.
+See also https://github.com/jenkinsci/jenkins/pull/4331#discussion_r341041470
+-->
+
 ## Testing changes
 
 Jenkins core includes unit and functional tests as a part of the repository.