title: Jenkins build output set as current build description
body: <p>I want to set current build description in my jenkins job from <code>#bash</code> output</p>
  
  <p>Jenkins build output set  as current build description  </p>
  
  <p>For example to set revision and branch from string and choice parameters I do it like this:  </p>
  
  <pre><code>   parameters {
         string(defaultValue: "", description: '11.00', name: 'REVISION')
         choice(name: 'BRANCH', choices: 'trunk\nupdate', description: 'Branch')
     }
  
     stage('Set build') {
        steps {
           script {
               // Set build parameters
               currentBuild.description = "$REVISION $BRANCH"
           }
        }
     }
  </code></pre>
  
  <p>Let's say that I want get my diskspace % <code>#bash</code> execution and put it in the description...</p>
  
  <pre><code>   stage('bash') {
        steps {
           script {
           sh '''
              DISK_SIZE="$(df -h --output='pcent' /mnt | grep -v "Use%")
           }
          currentBuild.description = "$DISK_SIZE"
        }
     }
  </code></pre>
  
  <p>I want in the build description for example to put my disk%. In this case I expect to in the description <code>%30</code></p>
  
  <p>Or to put some other staff that are generated from current build.</p>