applied a patch for #1348

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@7732 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/AbstractProject.java

@@ -588,19 +588,24 @@ public abstract class AbstractProject<P extends AbstractProject<P,R>,R extends A
         }
 
         try {
-            FilePath workspace = getWorkspace();
-            if(workspace==null) {
-                // workspace offline. build now, or nothing will ever be built
-                listener.getLogger().println(Messages.AbstractProject_WorkspaceOffline());
-                return true;
-            }
-            if(!workspace.exists()) {
-                // no workspace. build now, or nothing will ever be built
-                listener.getLogger().println(Messages.AbstractProject_NoWorkspace());
-                return true;
-            }
-
-            return scm.pollChanges(this, workspace.createLauncher(listener), workspace, listener );
+        	FilePath workspace = getWorkspace();
+        	if (scm.requiresWorkspaceForPolling()) {
+        		if(workspace==null) {
+        			// workspace offline. build now, or nothing will ever be built
+        			listener.getLogger().println("Workspace is offline.");
+        			listener.getLogger().println("Scheduling a new build to get a workspace.");
+        			return true;
+        		}
+        		if(!workspace.exists()) {
+        			// no workspace. build now, or nothing will ever be built
+        			listener.getLogger().println("No workspace is available, so can't check for updates.");
+        			listener.getLogger().println("Scheduling a new build to get a workspace.");
+        			return true;
+        		}
+        	}
+
+        	Launcher launcher = workspace != null ? workspace.createLauncher(listener) : null;
+            return scm.pollChanges(this, launcher, workspace, listener );
         } catch (AbortException e) {
             listener.fatalError(Messages.AbstractProject_Aborted());
             return false;

core/src/main/java/hudson/scm/SCM.java

@@ -80,6 +80,26 @@ public abstract class SCM implements Describable<SCM>, ExtensionPoint {
     public boolean supportsPolling() {
         return true;
     }
+    
+    /**
+     * Returns true if this SCM requires a checked out workspace for doing polling.
+     *
+     * <p>
+     * This flag affects the behavior of Hudson when a job lost its workspace
+     * (typically due to a slave outage.) If this method returns false and
+     * polling is configured, then that would immediately trigger a new build.
+     *
+     * <p>
+     * The default implementation returns true.
+     *
+     * <p>
+     * See issue #1348 for more discussion of this feature.
+     *
+     * @since 1.196
+     */
+    public boolean requiresWorkspaceForPolling() {
+    	return true;
+    }
 
     /**
      * Checks if there has been any changes to this module in the repository.

core/src/main/java/hudson/scm/SubversionSCM.java

@@ -55,6 +55,7 @@ import org.tmatesoft.svn.core.io.SVNRepositoryFactory;
 import org.tmatesoft.svn.core.wc.SVNClientManager;
 import org.tmatesoft.svn.core.wc.SVNInfo;
 import org.tmatesoft.svn.core.wc.SVNRevision;
+import org.tmatesoft.svn.core.wc.SVNStatus;
 import org.tmatesoft.svn.core.wc.SVNUpdateClient;
 import org.tmatesoft.svn.core.wc.SVNWCClient;
 import org.tmatesoft.svn.core.wc.SVNWCUtil;
@@ -1355,4 +1356,12 @@ public class SubversionSCM extends SCM implements Serializable {
 
         ch.ethz.ssh2.log.Logger.logLevel = 100;
     }
+
+    /**
+     * Polling can happen on the master and does not require a workspace.
+     */
+	@Override
+	public boolean requiresWorkspaceForPolling() {
+		return false;
+	}
 }