src/vs/workbench/browser/dnd.ts/ResourceListDnDHandler/getDragLabel
class ResourceListDnDHandler:	getDragLabel(elements: T[]): string | undefined {
		const resources = coalesce(elements.map(this.toResource));
		return resources.length === 1 ? basename(resources[0]) : resources.length > 1 ? String(resources.length) : undefined;
	}