src/vs/workbench/api/common/extHostFileSystem.ts/ExtHostFileSystem/$copy
class ExtHostFileSystem:	$copy(handle: number, oldUri: UriComponents, newUri: UriComponents, opts: files.IFileOverwriteOptions): Promise<void> {
		const provider = this._getFsProvider(handle);
		if (!provider.copy) {
			throw new Error('FileSystemProvider does not implement "copy"');
		}
		return Promise.resolve(provider.copy(URI.revive(oldUri), URI.revive(newUri), opts));
	}