pipeline {
    agent any

    stages {
        stage('TEST') {
            steps {
                script {
                    CUSTOM_TAG = sh(returnStdout: true, script: "git tag --contains").trim()
                    echo CUSTOM_TAG
                }
                echo sh(script: 'env|sort', returnStdout: true)
                echo "${CUSTOM_TAG}"
            }
        }
        stage('ONLY ON TAG') {
            when { buildingTag() }
            steps {
                echo "I run only because I am on tag ${CUSTOM_TAG}"
            }
        }
    }
}