fetch branches before master checkout

Jenkinsfile

@@ -47,6 +47,10 @@ node('docker') {
           // commit changes
           sh "git -c user.name='CES Marvin' -c user.email='cesmarvin@cloudogu.com' commit -m 'release version ${releaseVersion}'"
 
+          // we need to fetch all branches, so we can checkout master and develop later
+          sh "git config 'remote.origin.fetch +refs/heads/*:refs/remotes/origin/*'"
+          sh "git fetch --all"
+
           // merge release branch into master
           sh "git checkout master"
           sh "git merge --ff-only ${env.BRANCH_NAME}"