Hudson: Git and Maven plugins

Suddenly, something went wrong .. 😦
A usual Hudson job pulling sources from Git repository started to fail with NPE:

Parsing POMs
[nexttags-CI] $ c:\Winny\java\jdk1.6.0_18\/bin/java -Xmx1024m -XX:MaxPermSize=512m -cp c:\dev\hudson-slave\maven-agent.jar;C:\Winny\java\apache-maven-2.2.1\boot\classworlds-1.1.jar hudson.maven.agent.Main C:\Winny\java\apache-maven-2.2.1 C:\dev\hudson-slave\slave.jar c:\dev\hudson-slave\maven-interceptor.jar 3841 c:\dev\hudson-slave\maven2.1-interceptor.jar
<===[HUDSON REMOTING CAPACITY]===>channel started
channel stopped
ERROR: Processing failed due to a bug in the code. Please report this to users@hudson.dev.java.net
java.lang.NullPointerException
	at java.util.Hashtable.put(Hashtable.java:394)
	at java.util.Hashtable.putAll(Hashtable.java:466)
	at hudson.maven.MavenBuilder.call(MavenBuilder.java:156)
	at hudson.maven.MavenModuleSetBuild$Builder.call(MavenModuleSetBuild.java:688)
	at hudson.maven.MavenModuleSetBuild$Builder.call(MavenModuleSetBuild.java:632)
	at hudson.remoting.UserRequest.perform(UserRequest.java:114)
	at hudson.remoting.UserRequest.perform(UserRequest.java:48)
	at hudson.remoting.Request$2.run(Request.java:270)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:619)

What ?! But it worked half an hour ago. Hmm, that’s interesting …

After re-installing Hudson from scratch, installing it locally on my machine, going back and forward with versions, creating simple jobs doing absolutely nothing except pulling sources from various Git projects and running "mvn clean" .. I still couldn’t git rid of this error.

Well, it was clearly time for some debugging and .. here we go!

For some reason Git plugin started to pass null value for GIT_BRANCH environment variable.
This caused Maven plugin to fail in System.getProperties().putAll(systemProps) call.

The solution was to use "master" as default Git branch instead of "**" or empty String:

My versions were: Hudson v1.352, Git plugin v0.8.1

P.S
Some Hudson links:

• SVN repo (user: “guest”, empty password)
• Various ways to get and view Hudson sources
• Hudson downloads – application itself and plugins, all versions
• Hudson Git plugin
• “Continuous Integration with Hudson” – book in progress