Project Explorer: auto-expand long paths of single elements #1063

This commit enables auto-expansion of paths of elements with single
children in the project explorer.
In order not to accidentally lazy-load a big amount of files,
the auto-expansion is limited to a depth of 10 elements.

Implements #1063

bundles/org.eclipse.ui.navigator.resources/src/org/eclipse/ui/navigator/resources/ProjectExplorer.java

@@ -28,6 +28,7 @@
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.core.runtime.IStatus;
 import org.eclipse.core.runtime.SafeRunner;
+import org.eclipse.jface.viewers.AbstractTreeViewer;
 import org.eclipse.jface.viewers.DoubleClickEvent;
 import org.eclipse.jface.viewers.ILabelProvider;
 import org.eclipse.jface.viewers.IStructuredSelection;
@@ -84,6 +85,14 @@
 @SuppressWarnings("restriction")
 public final class ProjectExplorer extends CommonNavigator implements ISecondarySaveableSource {
 
+	/**
+	 * Number of levels to automatically expand when an element only has a single
+	 * child.
+	 *
+	 * @see AbstractTreeViewer#setAutoExpandOnSingleChildLevels(int)
+	 */
+	private static final int AUTO_EXPAND_ON_SINGLE_CHILD_LEVEL_COUNT = 10;
+
 	/**
 	 * Provides a constant for the standard instance of the Common Navigator.
 	 *
@@ -164,6 +173,7 @@ public void createPartControl(Composite aParent) {
 		if (this.userFilters.stream().anyMatch(UserFilter::isEnabled)) {
 			getCommonViewer().refresh();
 		}
+		getCommonViewer().setAutoExpandOnSingleChildLevels(AUTO_EXPAND_ON_SINGLE_CHILD_LEVEL_COUNT);
 	}
 
 	@Override