A function to cancel previous builds from the same GitLab merge request

gitlab_cancel_builds.groovy

def cancelBuilds(int builds_to_scan=300) {
    def jobName = env.JOB_NAME
    def currentMR = env.gitlabMergeRequestIid?.toInteger()
    def currentRepoUrl = env.gitlabSourceRepoURL
    def currentBuildNumber = env.BUILD_NUMBER?.toInteger()
    def currentJob = Jenkins.instance.getItemByFullName(jobName)

    def i = 0
    for (def build : currentJob.builds) {
        if (i > builds_to_scan) {
            return null
        }
        def buildNumber = build.number?.toInteger()
        if (buildNumber < currentBuildNumber) {
            def buildMR = build.getEnvVars()["gitlabMergeRequestIid"]?.toInteger()
            def buildRepoUrl = build.getEnvVars()["gitlabSourceRepoURL"]

            if (build.isBuilding() && buildMR == currentMR && buildRepoUrl == currentRepoUrl) {
                def executor = build.getExecutor()
                def cause = new CauseOfInterruption.UserInterruption(
                    "New pre-commit build was started for current MR ${buildMR} " +
                        "(see ${this.script.env.BUILD_URL}), current build is aborted"
                )
                executor.interrupt(Result.ABORTED, cause)
                return buildNumber
            }
        }
        i++
    }
}