Fix: Only show Add/Remove Hashtags UI elements if user has capability

The "Add #..." button is visible regardless if the user can add new
hashtags or not.

Already existing hashtags will also display a remove hashtag (×)
button when the user does not have the capability to edit hashtags.

Correct the UI to only show these elements when the user has the
necessary capability.

Change-Id: I6ad104f06f3c9ce4fffb8cdbe8a26b7f59381149

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Actions.java

@@ -38,7 +38,7 @@ class Actions extends Composite {
   private static final String[] CORE = {
     "abandon", "restore", "revert", "topic",
     "cherrypick", "submit", "rebase", "message",
-    "publish", "followup", "/"};
+    "publish", "followup", "hashtags", "/"};
 
   interface Binder extends UiBinder<FlowPanel, Actions> {}
   private static final Binder uiBinder = GWT.create(Binder.class);

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/Hashtags.java

@@ -51,6 +51,8 @@ public class Hashtags extends Composite {
   private static final String REMOVE;
   private static final String DATA_ID = "data-id";
 
+  private boolean canEdit;
+
   static {
     REMOVE = DOM.createUniqueId().replace('-', '_');
     init(REMOVE);
@@ -121,9 +123,10 @@ public class Hashtags extends Composite {
   }
 
   void set(ChangeInfo info) {
+    canEdit = info.has_actions() && info.actions().containsKey("hashtags");
     this.changeId = info.legacy_id();
     display(info);
-    openForm.setVisible(Gerrit.isSignedIn());
+    openForm.setVisible(canEdit);
   }
 
   @UiHandler("openForm")
@@ -165,13 +168,15 @@ public class Hashtags extends Composite {
               "#" + PageLinks.toChangeQuery("hashtag:\"" + hashtagName + "\""))
           .setAttribute("role", "listitem")
           .append("#").append(hashtagName)
-          .closeAnchor()
-          .openElement("button")
-          .setAttribute("title", "Remove hashtag")
-          .setAttribute("onclick", REMOVE + "(event)")
-          .append("×")
-          .closeElement("button")
-          .closeSpan();
+          .closeAnchor();
+      if (canEdit) {
+        html.openElement("button")
+            .setAttribute("title", "Remove hashtag")
+            .setAttribute("onclick", REMOVE + "(event)")
+            .append("×")
+            .closeElement("button");
+      }
+      html.closeSpan();
       if (itr.hasNext()) {
         html.append(' ');
       }

gerrit-server/src/main/java/com/google/gerrit/server/change/PostHashtags.java

@@ -20,6 +20,7 @@ import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.ResourceConflictException;
 import com.google.gerrit.extensions.restapi.Response;
 import com.google.gerrit.extensions.restapi.RestModifyView;
+import com.google.gerrit.extensions.webui.UiAction;
 import com.google.gerrit.server.validators.ValidationException;
 import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
@@ -29,7 +30,8 @@ import java.io.IOException;
 import java.util.Set;
 
 @Singleton
-public class PostHashtags implements RestModifyView<ChangeResource, HashtagsInput> {
+public class PostHashtags implements RestModifyView<ChangeResource, HashtagsInput>,
+    UiAction<ChangeResource>{
   private HashtagsUtil hashtagsUtil;
 
   @Inject
@@ -51,4 +53,11 @@ public class PostHashtags implements RestModifyView<ChangeResource, HashtagsInpu
       throw new ResourceConflictException(e.getMessage());
     }
   }
-}
+
+  @Override
+  public UiAction.Description getDescription(ChangeResource resource) {
+    return new UiAction.Description()
+      .setLabel("Edit Hashtags")
+      .setVisible(resource.getControl().canEditHashtags());
+  }
+}