improved the error message.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@3810 71c3de6d-444a-0410-be80-ed276b4c234a

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

@@ -312,7 +312,7 @@ public class CVSSCM extends SCM implements Serializable {
         File[] files = dir.listFiles();
         if(files==null) {
             if(isRoot)
-                throw new IOException("No such directory exists. Did you specify the correct branch/tag?: "+dir);
+                throw new IOException("No such directory exists. Did you specify the correct branch? Perhaps you specified a tag: "+dir);
             else
                 throw new IOException("No such directory exists. Looks like someone is modifying the workspace concurrently: "+dir);
         }