Implement a 'cleanWorkspace' option for wrappedNode

Author: mikedougherty

vars/wrappedNode.groovy

@@ -5,6 +5,15 @@ def call(Map vars, Closure body=null) {
       withDockerRegistry(url: vars.get("registryUrl", "https://index.docker.io/v1/"), credentialsId: vars.get("registryCreds", "dockerbuildbot-index.docker.io")) {
         wrap([$class: 'TimestamperBuildWrapper']) {
           wrap([$class: 'AnsiColorBuildWrapper']) {
+            if (vars.get('cleanWorkspace', false)) {
+              // NOTE: `withChownWorkspace` uses docker. if our `label` doesn't have docker
+              // or is misconfigured, these operations will fail and the exception will be
+              // propogated.
+              withChownWorkspace { echo "cleanWorkspace: Ensuring workspace is owned by ${env.USER}" }
+              echo "cleanWorkspace: Removing existing workspace"
+              deleteDir()
+              echo "cleanWorkspace: Workspace is clean."
+            }
             if (body) { body() }
           }
         }

vars/wrappedNode.txt

@@ -1,10 +1,11 @@
-<strong>wrappedNode(label: null, registryCreds: "dockerbuildbot-index.docker.io") { ... }</strong>
+<strong>wrappedNode(label: null, registryCreds: "dockerbuildbot-index.docker.io", cleanWorkspace: false) { ... }</strong>
 
 <p>
 Runs the given closure on a node matching <code>label</code> with the following behaviors:
 <ul>
 <li>Timestamps in build output</li>
 <li>Colored output</li>
-<li>Logged into the Docker Registry with the credentials specified by thegiven ID</li>
+<li>Logged into the Docker Registry with the credentials specified by the given ID</li>
+<li>If cleanWorkspace is true, the workspace is removed (chowning the directory first).</li>
 </ul>
 </p>