Fixes microsoft#161967 (microsoft#162165)

Author: hediet

src/vs/workbench/contrib/mergeEditor/browser/view/mergeEditor.ts

@@ -278,6 +278,10 @@ export class MergeEditor extends AbstractTextEditor<IMergeEditorViewState> {
 					return;
 				}
 				this.input1View.editor.revealLineInCenter(firstConflict.input1Range.startLineNumber);
+				transaction(tx => {
+					/** @description setActiveModifiedBaseRange */
+					viewModel.setActiveModifiedBaseRange(firstConflict, tx);
+				});
 			}));
 		}
 

src/vs/workbench/contrib/mergeEditor/browser/view/viewModel.ts

@@ -124,6 +124,10 @@ export class MergeEditorViewModel extends Disposable {
 		}
 	);
 
+	public setActiveModifiedBaseRange(range: ModifiedBaseRange | undefined, tx: ITransaction): void {
+		this.manuallySetActiveModifiedBaseRange.set({ range, counter: this.counter++ }, tx);
+	}
+
 	public setState(
 		baseRange: ModifiedBaseRange,
 		state: ModifiedBaseRangeState,