git clone https://github.com/jenkinsci/jenkins.git
cd jenkins
mvn clean
mvn install -Dmavem.test.skip=true -DskipTests
cd war # this is important ! :)
# change pom.xml
# Remove following lines:
# <manifest>
# <mainClass>Main</mainClass>
# </manifest>
sed "/<\/manifest>/d" pom.xml | sed "/<manifest>/d" | sed "/<mainClass>Main<\/mainClass>/d" > pom.xml
mvn clean
mvn install -Dmavem.test.skip=true -DskipTests
cf push jenkins -p target/jenkins.war