show diff in "replace with local history" dialog on selection change

- disallow multi selection in "replace with local history" dialog
- fix layouting issue on MacOS when loading the compare viewers on
selection change

team/bundles/org.eclipse.team.ui/src/org/eclipse/team/internal/ui/history/LocalHistoryPage.java

@@ -336,9 +336,7 @@ private IWorkbenchPartSite getWorkbenchSite(IHistoryPageSite parentSite) {
 		return null;
 	}
 
-	@Override
-	public void createControl(Composite parent) {
-
+	public final void createControl(Composite parent, boolean allowMultiSelection) {
 		localComposite = new Composite(parent, SWT.NONE);
 		GridLayout layout = new GridLayout();
 		layout.marginHeight = 0;
@@ -348,7 +346,7 @@ public void createControl(Composite parent) {
 		data.grabExcessVerticalSpace = true;
 		localComposite.setLayoutData(data);
 
-		treeViewer = createTree(localComposite);
+		treeViewer = createTree(localComposite, allowMultiSelection);
 
 		contributeActions();
 
@@ -362,6 +360,11 @@ public void createControl(Composite parent) {
 		PlatformUI.getWorkbench().getHelpSystem().setHelp(localComposite, IHelpContextIds.LOCAL_HISTORY_PAGE);
 	}
 
+	@Override
+	public void createControl(Composite parent) {
+		createControl(parent, true);
+	}
+
 	private void contributeActions() {
 		final IPreferenceStore store = TeamUIPlugin.getPlugin().getPreferenceStore();
 		//Group by Date
@@ -599,8 +602,12 @@ private boolean showGetContentsAction(ITreeSelection sel) {
 	 * @return the group control
 	 */
 	protected TreeViewer createTree(Composite parent) {
+		return createTree(parent, true);
+	}
+
+	protected final TreeViewer createTree(Composite parent, boolean allowMultiSelection) {
 		historyTableProvider = new LocalFileHistoryTableProvider();
-		TreeViewer viewer = historyTableProvider.createTree(parent);
+		TreeViewer viewer = historyTableProvider.createTree(parent, allowMultiSelection);
 		viewer.setContentProvider(new LocalHistoryContentProvider());
 		return viewer;
 	}

team/bundles/org.eclipse.team.ui/src/org/eclipse/team/internal/ui/history/LocalHistoryTableProvider.java

@@ -291,7 +291,15 @@ public void widgetSelected(SelectionEvent e) {
 	 * @return TableViewer
 	 */
 	public TreeViewer createTree(Composite parent) {
-		Tree tree = new Tree(parent, SWT.H_SCROLL | SWT.V_SCROLL | SWT.MULTI | SWT.FULL_SELECTION);
+		return createTree(parent, true);
+	}
+
+	public TreeViewer createTree(Composite parent, boolean allowMultiSelection) {
+		int style = SWT.H_SCROLL | SWT.V_SCROLL | SWT.FULL_SELECTION;
+		if (allowMultiSelection) {
+			style = style | SWT.MULTI;
+		}
+		Tree tree = new Tree(parent, style);
 		tree.setHeaderVisible(true);
 		tree.setLinesVisible(false);
 

team/bundles/org.eclipse.team.ui/src/org/eclipse/team/internal/ui/history/ReplaceLocalHistory.java

@@ -13,19 +13,33 @@
  *******************************************************************************/
 package org.eclipse.team.internal.ui.history;
 
+import java.lang.reflect.InvocationTargetException;
+
 import org.eclipse.compare.CompareConfiguration;
 import org.eclipse.compare.CompareUI;
+import org.eclipse.compare.CompareViewerPane;
 import org.eclipse.compare.structuremergeviewer.ICompareInput;
 import org.eclipse.core.resources.IFile;
 import org.eclipse.core.resources.IFileState;
 import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.NullProgressMonitor;
 import org.eclipse.jface.action.IAction;
+import org.eclipse.jface.action.IToolBarManager;
+import org.eclipse.jface.operation.IRunnableWithProgress;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.SelectionAdapter;
+import org.eclipse.swt.events.SelectionEvent;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Control;
+import org.eclipse.swt.widgets.Event;
 import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Tree;
 import org.eclipse.team.internal.ui.TeamUIMessages;
 import org.eclipse.team.internal.ui.TeamUIPlugin;
 import org.eclipse.team.internal.ui.Utils;
 import org.eclipse.team.ui.history.HistoryPageCompareEditorInput;
 import org.eclipse.team.ui.history.IHistoryPageSource;
+import org.eclipse.ui.part.IPage;
 
 public class ReplaceLocalHistory extends ShowLocalHistory {
 
@@ -46,6 +60,14 @@ private void showCompareInDialog(Shell shell, Object object){
 			cc.setLeftEditable(false);
 			cc.setRightEditable(false);
 			HistoryPageCompareEditorInput input = new HistoryPageCompareEditorInput(cc, pageSource, object) {
+				@Override
+				public void run(boolean fork, boolean cancelable, IRunnableWithProgress runnable)
+						throws InvocationTargetException, InterruptedException {
+					// Avoid using super.run() on macOS as it causes layout issues.
+					// The compare viewer controls appear small and do not fill the entire dialog.
+					runnable.run(new NullProgressMonitor());
+				}
+
 				@Override
 				public boolean isEditionSelectionDialog() {
 					return true;
@@ -54,6 +76,48 @@ public boolean isEditionSelectionDialog() {
 				public String getOKButtonLabel() {
 					return TeamUIMessages.ReplaceLocalHistory_0;
 				}
+
+				@Override
+				protected IPage createPage(CompareViewerPane parent, IToolBarManager toolBarManager) {
+					var page = super.createPage(parent, toolBarManager, false);
+					Tree tree = getTree(page);
+					runDefaultSelectionEventOnSelectionChange(tree);
+					return page;
+				}
+
+				private void runDefaultSelectionEventOnSelectionChange(Tree tree) {
+					if (tree == null) {
+						return;
+					}
+					tree.addSelectionListener(new SelectionAdapter() {
+
+						@Override
+						public void widgetSelected(SelectionEvent e) {
+							if (tree.getSelectionCount() != 1) {
+								return;
+							}
+							Event event = new Event();
+							event.item = e.item;
+							tree.notifyListeners(SWT.DefaultSelection, event);
+						}
+					});
+				}
+				private Tree getTree(IPage page) {
+					Control control = page.getControl();
+					if (!(control instanceof Composite composite)) {
+						return null;
+					}
+					Control[] children = composite.getChildren();
+					if (children == null) {
+						return null;
+					}
+					for (Control child : children) {
+						if (child instanceof Tree t) {
+							return t;
+						}
+					}
+					return null;
+				}
 				@Override
 				public boolean okPressed() {
 					try {

team/bundles/org.eclipse.team.ui/src/org/eclipse/team/ui/history/HistoryPageCompareEditorInput.java

@@ -31,6 +31,7 @@
 import org.eclipse.team.internal.ui.TeamUIMessages;
 import org.eclipse.team.internal.ui.Utils;
 import org.eclipse.team.internal.ui.history.DialogHistoryPageSite;
+import org.eclipse.team.internal.ui.history.LocalHistoryPage;
 import org.eclipse.team.ui.PageCompareEditorInput;
 import org.eclipse.ui.part.IPage;
 import org.eclipse.ui.part.Page;
@@ -79,11 +80,20 @@ protected void handleDispose() {
 
 	@Override
 	protected IPage createPage(CompareViewerPane parent, IToolBarManager toolBarManager) {
+		return createPage(parent, toolBarManager, true);
+	}
+
+	protected final IPage createPage(CompareViewerPane parent, IToolBarManager toolBarManager,
+			boolean allowMultiSelection) {
 		site = new DialogHistoryPageSite(parent.getShell());
 		historyPage = (IHistoryPage)pageSource.createPage(object);
 		historyPage.setSite(site);
 		site.setToolBarManager(toolBarManager);
-		((Page) historyPage).createControl(parent);
+		if (historyPage instanceof LocalHistoryPage localHistoryPage) {
+			localHistoryPage.createControl(parent, allowMultiSelection);
+		} else {
+			((Page) historyPage).createControl(parent);
+		}
 		historyPage.setInput(object);
 		String description = historyPage.getDescription();
 		if (description == null)