Sample structure for optional pipeline steps

#!groovy

/* Sample structure for optional parametrized DDSL pipeline steps
 * Copyright (C) 2016 by Jim Klimov on the terms of MIT license
 */
pipeline {
    agent label:"myproject-builder"
    parameters {
        booleanParam(defaultValue: false, description: 'Removes workspace completely before checkout and build', name: 'action_DistcleanRebuild')
        booleanParam(defaultValue: false, description: 'Wipes untracked files from workspace before checkout and build', name: 'action_GitcleanRebuild')
        booleanParam(defaultValue: true,  description: 'Run Git to checkout or update the project sources', name: 'action_DoSCM')
/* other boolean toggles and/or string parameter definitions for prep, build, check, publish, etc. stages and other behaviors */
    }
    stages {
        stage("WORKSPACE:DESTROY") {
            when {
                if (params["action_DistcleanRebuild"] == true) {
                    if (fileExists(file: "${env.WORKSPACE}/.git/config")) {
                        return true;
                    }
                }
                return false;
            }
            steps {
                echo "Removing '${env.WORKSPACE}' at '${env.NODE_NAME}'"
                dir("${env.WORKSPACE}") {
                    deleteDir()
                }
            }
        }
        stage("WORKSPACE:GITWIPE") {
            when {
                if (params["action_DistcleanRebuild"] == false && params["action_GitcleanRebuild"] == true) {
                    if (fileExists(file: "${env.WORKSPACE}/.git/config")) {
                        return true;
                    }
                }
                return false;
            }
            steps {
                dir("${env.WORKSPACE}") {
                    echo "Git-cleaning '${env.WORKSPACE}' at '${env.NODE_NAME}'"
                    sh 'git checkout -f'
                    sh 'git clean -d -ff -x'
                }
            }
            post {
                failure {
                    echo "ERROR: Git clean failed in '${env.WORKSPACE}' at '${env.NODE_NAME}', removing workspace completely"
                    dir("${env.WORKSPACE}") {
                        deleteDir()
                    }
                }
            }
        }
        stage("WORKSPACE:CHECKOUT") {
            when {
                params["action_DoSCM"] == true
            }
            steps {
                sh "mkdir -p '${env.WORKSPACE}'"
                checkout scm
            }
        }
/* other stages for prep, build, check, publish, etc. */
    }
}