Run docker build and deployment only for main branch

Jenkinsfile

@@ -48,20 +48,21 @@ node('docker') {
       def commitHash = getCommitHash()
       def dockerImageTag = "2.0.0-dev-${commitHash.substring(0,7)}-${BUILD_NUMBER}"
 
-      stage('Docker') {
-        // TODO only on mainBranch
-        def image = docker.build('cloudogu/scm-manager')
-        docker.withRegistry('', 'hub.docker.com-cesmarvin') {
-          image.push(dockerImageTag)
-          image.push('latest')
+      if (isMainBranch()) {
+        stage('Docker') {
+          def image = docker.build('cloudogu/scm-manager')
+          docker.withRegistry('', 'hub.docker.com-cesmarvin') {
+            image.push(dockerImageTag)
+            image.push('latest')
+          }
         }
-      }
 
-      stage('Deployment') {
-        build job: 'scm-manager/next-scm.cloudogu.com', propagate: false, wait: false, parameters: [
-          string(name: 'changeset', value: commitHash), 
-          string(name: 'imageTag', value: dockerImageTag)
-        ]
+        stage('Deployment') {
+          build job: 'scm-manager/next-scm.cloudogu.com', propagate: false, wait: false, parameters: [
+            string(name: 'changeset', value: commitHash),
+            string(name: 'imageTag', value: dockerImageTag)
+          ]
+        }
       }
     }
 
@@ -81,7 +82,7 @@ Maven setupMavenBuild() {
   // Keep this version number in sync with .mvn/maven-wrapper.properties
   Maven mvn = new MavenInDocker(this, "3.5.2-jdk-8")
 
-  if (mainBranch.equals(env.BRANCH_NAME)) {
+  if (isMainBranch()) {
     // Release starts javadoc, which takes very long, so do only for certain branches
     mvn.additionalArgs += ' -DperformRelease'
     // JDK8 is more strict, we should fix this before the next release. Right now, this is just not the focus, yet.
@@ -108,7 +109,7 @@ void analyzeWith(Maven mvn) {
         "-Dsonar.pullrequest.bitbucketcloud.repository=scm-manager "
     } else {
       mvnArgs += " -Dsonar.branch.name=${env.BRANCH_NAME} "
-      if (!mainBranch.equals(env.BRANCH_NAME)) {
+      if (!isMainBranch()) {
         // Avoid exception "The main branch must not have a target" on main branch
         mvnArgs += " -Dsonar.branch.target=${mainBranch} "
       }
@@ -117,6 +118,10 @@ void analyzeWith(Maven mvn) {
   }
 }
 
+boolean isMainBranch() {
+  return mainBranch.equals(env.BRANCH_NAME)
+}
+
 boolean waitForQualityGateWebhookToBeCalled() {
   boolean isQualityGateSucceeded = true
   timeout(time: 2, unit: 'MINUTES') { // Needed when there is no webhook for example