Better impl of getRootBuild in case the promoted build was e.g. a MatrixRun.
Comment.
[FIXED JENKINS-13248] Now possible to use the REST API to determine which build a promotion promoted.
E.g.: http://localhost:8080/job/j/promotion/latest/OK/api/json?tree=target[number]
Hyperlinking processes for discoverability.
[FIXED JENKINS-15947] Make it possible to obtain list of promotions via REST.
[FIXED JENKINS-9259] Include information about promotions in the REST API for each build.