Return text/uri-list if ?part= is missing

This is part of #176

Author: stain

src/main/java/org/commonwl/view/workflow/WorkflowService.java

@@ -396,23 +396,46 @@ public void retryCwltool(QueuedWorkflow queuedWorkflow) {
      * @return A workflow model with the above two parameters
      */
     public Workflow findByCommitAndPath(String commitID, String path) throws WorkflowNotFoundException {
+        return findByCommitAndPath(commitID, path, Optional.empty());
+    }
+
+    /**
+     * Find a workflow by commit ID and path
+     *
+     * @param commitID
+     *            The commit ID of the workflow
+     * @param path
+     *            The path to the workflow within the repository
+     * @param part
+     *            The #part within the workflow, or Optional.empty() for no part, or
+     *            <code>null</code> for any part
+     * @return A workflow model with the above two parameters
+     */
+    public Workflow findByCommitAndPath(String commitID, String path, Optional<String> part)
+            throws WorkflowNotFoundException, MultipleWorkflowsException {
         List<Workflow> matches = workflowRepository.findByCommitAndPath(commitID, path);
-        if (matches == null || matches.size() == 0) {
+        if (matches == null || matches.isEmpty()) {
             throw new WorkflowNotFoundException();
-        } else if (matches.size() == 1) {
+        } else if (part == null) {
+            // any part will do - so we'll pick the first one
             return matches.get(0);
         } else {
             // Multiple matches means either added by both branch and ID
             // Or packed workflow
             for (Workflow workflow : matches) {
-                if (workflow.getRetrievedFrom().getPackedId() != null) {
-                    // This is a packed file
-                    // TODO: return 300 multiple choices response for this in controller
-                    throw new WorkflowNotFoundException();
+                if (Objects.equals(part.orElse(null), workflow.getRetrievedFrom().getPackedId())) {
+                    // either both are null; or both are non-null and equal
+                    return workflow;
                 }
             }
-            // Not a packed workflow, just different references to the same ID
-            return matches.get(0);
+            if (part.isPresent()) {
+                // Sorry, don't know about your part!
+                throw new WorkflowNotFoundException();
+            } else {
+                // No part requested, let's show some alternate permalinks,
+                // in addition to the raw redirect
+                throw new MultipleWorkflowsException(matches);
+            }
         }
     }