use internal changelog library

Jenkinsfile

@@ -1,11 +1,9 @@
 #!/usr/bin/env groovy
 
 node('master') {
-    checkout scm
-    passedBuilds = []
-    def changelog = lastSuccessfulBuild(passedBuilds, currentBuild)
+    def changelog = getChangeLog currentBuild
 
-    slackSend "Building ${env.JOB_NAME} #${env.BUILD_NUMBER} \n ${changelog}"
+    slackSend "Building ${env.JOB_NAME} #${env.BUILD_NUMBER} \n Change Log: \n ${changelog}"
 }
 
 parallel 'centos7': {
@@ -63,27 +61,3 @@ parallel 'centos7': {
 }
 
 slackSend "${env.JOB_NAME} #${env.BUILD_NUMBER} Complete (<${env.BUILD_URL}|Show More...>)"
-
-def lastSuccessfulBuild(passedBuilds, build) {
-  if ((build != null) && (build.result != 'SUCCESS')) {
-      passedBuilds.add(build)
-      lastSuccessfulBuild(passedBuilds, build.getPreviousBuild())
-   }
-}
-
-@NonCPS
-def getChangeLog(passedBuilds) {
-    def log = ""
-    for (int x = 0; x < passedBuilds.size(); x++) {
-        def currentBuild = passedBuilds[x];
-        def changeLogSets = currentBuild.rawBuild.changeSets
-        for (int i = 0; i < changeLogSets.size(); i++) {
-            def entries = changeLogSets[i].items
-            for (int j = 0; j < entries.length; j++) {
-                def entry = entries[j]
-                log += "* ${entry.msg} by ${entry.author} \n"
-            }
-        }
-    }
-    return log;
-}