private void writeUserIncludeDirs(ApplicationPackage applicationPackage, List<String> userIncludeDirs) throws IOException {
            for (String userInclude : userIncludeDirs) {
                ApplicationFile dir = applicationPackage.getFile(Path.fromString(userInclude));
                final List<ApplicationFile> files = dir.listFiles();
                if (files == null || files.isEmpty()) {
                    curator.create(getZooKeeperAppPath(USERAPP_ZK_SUBPATH + "/" + userInclude));
                }
                writeDir(dir, getZooKeeperAppPath(USERAPP_ZK_SUBPATH + "/" + userInclude), xmlFilter);
            }
        }
Like {@link ApplicationFile#listFiles(ApplicationFile.PathFilter)}
with slightly different semantics: Never filter out directories.
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ZooKeeperDeployer.java