Jenkins Pipeline DSL code to demonstrate git merge before build

git-merge-before-build.dsl

// Jenkins Pipeline DSL to demonstrate git merge before build
node {
    String path = '/tmp/jenkins/upstream-repo'
    sh "rm -rf ${path}"
    ws(path) {
        sh 'git --version'
        sh 'git init'
        sh 'touch README.md; git add README.md; git commit -m "init"'
        sh 'git checkout -b pull-requests/1/from'
        sh 'touch file.txt; git add file.txt; git commit -m "Add file"'
    }
    // sh "git clone ${path} ."
    sh 'pwd; tree; ls;'
    checkout([
        $class: 'GitSCM',
        branches: [[name: 'refs/heads/master']],
        userRemoteConfigs: [[
            name: 'origin',
            refspec: 'pull-requests/1/from',
            url: path
        ]],
        extensions: [
        [
            $class: 'PreBuildMerge',
            options: [
                fastForwardMode: 'NO_FF',
                mergeRemote: 'origin',
                mergeStrategy: 'MergeCommand.Strategy',
                mergeTarget: 'master'
            ]
        ],
        [
            $class: 'LocalBranch',
            localBranch: 'master'
        ]]
    ])
    sh 'git log -n 10 --graph --pretty=oneline --abbrev-commit --all --decorate=full'
}