I couldn't find a way to distinguish between manually triggered and auto triggered jobs in my pipeline script, using tfs-plugin. What ever i trigger the build mannually or by a code push the result of "currentBuild.getBuildCauses()" : 
[\{"_class":"hudson.model.Cause$UserIdCause","shortDescription":"Démarré par l'utilisateur Admin Jenkins","userId":"admin","userName":"Admin Jenkins"}]
I think that the Cause class https://javadoc.jenkins-ci.org/hudson/model/Cause.html should be extended  to keep track of why a given build was started.