ChangeScreen2: Add 'Diff against' to select base revision

Add dropdown on the Files header section to select
reference version for loading the revision.

Change-Id: I5c40a52b0018fea7e11ac67696ee6fb7b4674349
(cherry picked from commit 2d2a3c405e)

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.java

@@ -58,6 +58,8 @@ import com.google.gwt.core.client.JsArrayString;
 import com.google.gwt.dom.client.AnchorElement;
 import com.google.gwt.dom.client.Element;
 import com.google.gwt.dom.client.NativeEvent;
+import com.google.gwt.dom.client.SelectElement;
+import com.google.gwt.event.dom.client.ChangeEvent;
 import com.google.gwt.event.dom.client.ClickEvent;
 import com.google.gwt.event.dom.client.ClickHandler;
 import com.google.gwt.event.dom.client.KeyPressEvent;
@@ -73,6 +75,7 @@ import com.google.gwt.user.client.rpc.AsyncCallback;
 import com.google.gwt.user.client.ui.Button;
 import com.google.gwt.user.client.ui.HTMLPanel;
 import com.google.gwt.user.client.ui.Image;
+import com.google.gwt.user.client.ui.ListBox;
 import com.google.gwt.user.client.ui.ToggleButton;
 import com.google.gwtexpui.clippy.client.CopyableLabel;
 import com.google.gwtexpui.globalkey.client.GlobalKey;
@@ -124,6 +127,7 @@ public class ChangeScreen2 extends Screen {
   private Timestamp lastDisplayedUpdate;
   private UpdateAvailableBar updateAvailable;
   private boolean openReplyBox;
+  private boolean loaded;
 
   @UiField HTMLPanel headerLine;
   @UiField Style style;
@@ -151,6 +155,7 @@ public class ChangeScreen2 extends Screen {
   @UiField CommitBox commit;
   @UiField RelatedChanges related;
   @UiField FileTable files;
+  @UiField ListBox diffBase;
   @UiField History history;
 
   @UiField Button includedIn;
@@ -185,7 +190,7 @@ public class ChangeScreen2 extends Screen {
       @Override
       public void onSuccess(ChangeInfo info) {
         info.init();
-        loadConfigInfo(info);
+        loadConfigInfo(info, null);
       }
     });
   }
@@ -194,9 +199,7 @@ public class ChangeScreen2 extends Screen {
     RestApi call = ChangeApi.detail(changeId.get());
     ChangeList.addOptions(call, EnumSet.of(
       ListChangesOption.CURRENT_ACTIONS,
-      fg && revision != null
-        ? ListChangesOption.ALL_REVISIONS
-        : ListChangesOption.CURRENT_REVISION));
+      ListChangesOption.ALL_REVISIONS));
     if (!fg) {
       call.background();
     }
@@ -444,25 +447,40 @@ public class ChangeScreen2 extends Screen {
     collapseAll.setVisible(false);
   }
 
-  private void loadConfigInfo(final ChangeInfo info) {
+  @UiHandler("diffBase")
+  void onChangeRevision(ChangeEvent e) {
+    int idx = diffBase.getSelectedIndex();
+    if (0 <= idx) {
+      String n = diffBase.getValue(idx);
+      loadConfigInfo(changeInfo, !n.isEmpty() ? n : null);
+    }
+  }
+
+  private void loadConfigInfo(final ChangeInfo info, final String base) {
     info.revisions().copyKeysIntoChildren("name");
     final RevisionInfo rev = resolveRevisionToDisplay(info);
 
     CallbackGroup group = new CallbackGroup();
-    loadDiff(rev, myLastReply(info), group);
+    loadDiff(info.revisions().get(base), rev, myLastReply(info), group);
     loadCommit(rev, group);
+
+    if (loaded) {
+      group.done();
+      return;
+    }
+
     RevisionInfoCache.add(changeId, rev);
     ConfigInfoCache.add(info);
     ConfigInfoCache.get(info.project_name_key(),
-      group.add(new ScreenLoadCallback<ConfigInfoCache.Entry>(this) {
+      group.addFinal(new ScreenLoadCallback<ConfigInfoCache.Entry>(this) {
         @Override
         protected void preDisplay(Entry result) {
+          loaded = true;
           commentLinkProcessor = result.getCommentLinkProcessor();
           setTheme(result.getTheme());
           renderChangeInfo(info);
         }
       }));
-    group.done();
   }
 
   private static Timestamp myLastReply(ChangeInfo info) {
@@ -478,16 +496,19 @@ public class ChangeScreen2 extends Screen {
     return null;
   }
 
-  private void loadDiff(final RevisionInfo rev, final Timestamp myLastReply,
-      CallbackGroup group) {
+  private void loadDiff(final RevisionInfo base, final RevisionInfo rev,
+      final Timestamp myLastReply, CallbackGroup group) {
     final List<NativeMap<JsArray<CommentInfo>>> comments = loadComments(rev, group);
     final List<NativeMap<JsArray<CommentInfo>>> drafts = loadDrafts(rev, group);
     DiffApi.list(changeId.get(),
+      base != null ? base.name() : null,
       rev.name(),
       group.add(new AsyncCallback<NativeMap<FileInfo>>() {
         @Override
         public void onSuccess(NativeMap<FileInfo> m) {
-          files.setRevisions(null, new PatchSet.Id(changeId, rev._number()));
+          files.setRevisions(
+              base != null ? new PatchSet.Id(changeId, base._number()) : null,
+              new PatchSet.Id(changeId, rev._number()));
           files.setValue(m, myLastReply, comments.get(0), drafts.get(0));
         }
 
@@ -653,6 +674,7 @@ public class ChangeScreen2 extends Screen {
 
     renderOwner(info);
     renderActionTextDate(info);
+    renderDiffBaseListBox(info);
     initIncludedInAction(info);
     initRevisionsAction(info, revision);
     initDownloadAction(info, revision);
@@ -728,6 +750,28 @@ public class ChangeScreen2 extends Screen {
     actionDate.setInnerText(FormatUtil.relativeFormat(info.updated()));
   }
 
+  private void renderDiffBaseListBox(ChangeInfo info) {
+    JsArray<RevisionInfo> list = info.revisions().values();
+    RevisionInfo.sortRevisionInfoByNumber(list);
+    for (int i = list.length() - 1; i >= 0; i--) {
+      RevisionInfo r = list.get(i);
+      diffBase.addItem(
+        r._number() + ": " + r.name().substring(0, 6),
+        r.name());
+      if (r.name().equals(revision)) {
+        SelectElement.as(diffBase.getElement()).getOptions()
+            .getItem(diffBase.getItemCount() - 1).setDisabled(true);
+      }
+    }
+
+    RevisionInfo rev = info.revisions().get(revision);
+    JsArray<CommitInfo> parents = rev.commit().parents();
+    diffBase.addItem(
+      parents.length() > 1 ? Util.C.autoMerge() : Util.C.baseDiffItem(),
+      "");
+    diffBase.setSelectedIndex(diffBase.getItemCount() - 1);
+  }
+
   void showUpdates(ChangeInfo newInfo) {
     if (!isAttached() || newInfo.updated().equals(lastDisplayedUpdate)) {
       return;

gerrit-gwtui/src/main/java/com/google/gerrit/client/change/ChangeScreen2.ui.xml

@@ -251,12 +251,27 @@ limitations under the License.
     .sectionHeader .headerButtons {
       top: 2px;
       height: 18px;
+      line-height: 18px;
       border-left: 1px inset #fff;
       padding-top: 3px;
       padding-bottom: 3px;
     }
     .sectionHeader button { margin-top: 0; }
 
+    .diffBase {
+      display: inline-block;
+      height: 18px;
+      line-height: 18px;
+      font-size: smaller;
+      font-weight: normal;
+      vertical-align: top;
+    }
+    .diffBase select {
+      margin: 0;
+      border: 1px solid #bbb;
+      font-size: smaller;
+    }
+
     .replyBox {
       background-color: trimColor;
     }
@@ -390,6 +405,11 @@ limitations under the License.
 
     <div class='{style.sectionHeader}'>
       <ui:msg>Files</ui:msg>
+      <div class='{style.headerButtons}'>
+        <div class='{style.diffBase}'>
+          <ui:msg>Diff against: <g:ListBox ui:field='diffBase' styleName=''/></ui:msg>
+        </div>
+      </div>
     </div>
     <c:FileTable ui:field='files'/>
 

gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/DiffApi.java

@@ -26,11 +26,13 @@ public class DiffApi {
     NONE, TRAILING, CHANGED, ALL;
   };
 
-  public static void list(int id, String revision,
+  public static void list(int id, String base, String revision,
       AsyncCallback<NativeMap<FileInfo>> cb) {
-    ChangeApi.revision(id, revision)
-      .view("files")
-      .get(NativeMap.copyKeysIntoChildren("path", cb));
+    RestApi api = ChangeApi.revision(id, revision).view("files");
+    if (base != null) {
+      api.addParameter("base", base);
+    }
+    api.get(NativeMap.copyKeysIntoChildren("path", cb));
   }
 
   public static DiffApi diff(PatchSet.Id id, String path) {