GitLab 事件触发 Jenkins 构建只是一个启动信号，获取变更文件列表需要知晓上一次构建时某个仓库的版本号，这里 Jenkins 的插件 git-plugin 已经帮我们实现了这部分工作。所以只需要通过 git-plugin 检出代码即可。

检出代码

    checkout([
        $class: 'GitSCM',
        branches: [[name: "*/$branchName"]],
        doGenerateSubmoduleConfigurations: false,
        extensions: [
            [$class: 'RelativeTargetDirectory',
            relativeTargetDir: "$relativeTarget"]
        ],
        submoduleCfg: [],
        userRemoteConfigs: [
            [credentialsId: "$credentialsId", url: "$gitUrl"]
        ]
    ])

请自行替换 $branchName 为分支名，$relativeTarget 为检出相对路径，$credentialsId 为用户凭据， $gitUrl 即 GIT仓库地址。

获取信息脚本demo

pipeline {
    agent any
    stages {
        stage('拉取代码') {
            steps {
                checkout([
			        $class: 'GitSCM',
			        branches: [[name: "*/$branchName"]],
			        doGenerateSubmoduleConfigurations: false,
			        extensions: [
			            [$class: 'RelativeTargetDirectory',
			            relativeTargetDir: "$relativeTarget"]
			        ],
			        submoduleCfg: [],
			        userRemoteConfigs: [
			            [credentialsId: "$credentialsId", url: "$gitUrl"]
			        ]
			    ])
            }
        }
        
		stage('构建代码') {
            steps {
				script{
                    List<String> changes = getChangedFilesList()
                    println ("文件变更列表: " + changes)
 
                    String gitCommitId = getGitcommitID()
                    println("CommitID: " + gitCommitID)
 
                    String gitCommitAuthorName = getAuthorName()
                    println("提交人: " + gitCommitAuthorName)
 
                    String gitCommitMessage = getCommitMessage()
                    println("提交信息: " + gitCommitMessage)
				}
            }
        }

    }
}

//获取变更文件列表，返回HashSet，注意添加的影响文件路径不含仓库目录名
@NonCPS
List<String> getChangedFilesList(){
    def changedFiles = []
    for ( changeLogSet in currentBuild.changeSets){
        for (entry in changeLogSet.getItems()){
            changedFiles.addAll(entry.affectedPaths)
        }
    }
    return changedFiles
}

// 获取提交ID
@NonCPS
String getGitcommitID(){
    gitCommitID = " "
    for ( changeLogSet in currentBuild.changeSets){
        for (entry in changeLogSet.getItems()){
            gitCommitID = entry.commitId
        }
    }
    return gitCommitID
}

// 获取提交人
@NonCPS
String getAuthorName(){
    gitAuthorName = " "
    for ( changeLogSet in currentBuild.changeSets){
        for (entry in changeLogSet.getItems()){
            gitAuthorName = entry.author.fullName
        }
    }
    return gitAuthorName
}

// 获取提交信息
@NonCPS
String getCommitMessage(){
    commitMessage = " "
    for ( changeLogSet in currentBuild.changeSets){
        for (entry in changeLogSet.getItems()){
            commitMessage = entry.msg
        }
    }
    return commitMessage
}