src/vs/workbench/contrib/files/browser/views/explorerView.ts/ExplorerView/collapseAll
class ExplorerView:	collapseAll(): void {
		if (this.explorerService.isEditable(undefined)) {
			this.tree.domFocus();
		}

		const treeInput = this.tree.getInput();
		if (Array.isArray(treeInput)) {
			if (hasExpandedRootChild(this.tree, treeInput)) {
				treeInput.forEach(folder => {
					folder.children.forEach(child => this.tree.hasNode(child) && this.tree.collapse(child, true));
				});

				return;
			}
		}

		this.tree.collapseAll();
	}