/*
    * Copyright (C) 2011, GitHub Inc.
    * and other copyright owners as documented in the project's IP log.
    *
    * This program and the accompanying materials are made available
    * under the terms of the Eclipse Distribution License v1.0 which
    * accompanies this distribution, is reproduced below, and is
    * available at http://www.eclipse.org/org/documents/edl-v10.php
    *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or
   * without modification, are permitted provided that the following
   * conditions are met:
   *
   * - Redistributions of source code must retain the above copyright
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   *
   * - Redistributions in binary form must reproduce the above
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   *   disclaimer in the documentation and/or other materials provided
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  package org.eclipse.jgit.submodule;
  
  import java.io.File;
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.eclipse.jgit.dircache.DirCache;
  import org.eclipse.jgit.dircache.DirCacheIterator;
  import org.eclipse.jgit.errors.ConfigInvalidException;
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.errors.RepositoryNotFoundException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.BlobBasedConfig;
  import org.eclipse.jgit.lib.Config;
  import org.eclipse.jgit.lib.ConfigConstants;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.FileMode;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.lib.RepositoryBuilder;
  import org.eclipse.jgit.lib.StoredConfig;
  import org.eclipse.jgit.storage.file.FileBasedConfig;
  import org.eclipse.jgit.treewalk.AbstractTreeIterator;
  import org.eclipse.jgit.treewalk.CanonicalTreeParser;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.treewalk.filter.PathFilter;
  import org.eclipse.jgit.treewalk.filter.TreeFilter;
  import org.eclipse.jgit.util.FS;
  
  /**
   * Walker that visits all submodule entries found in a tree
   */
  public class SubmoduleWalk implements AutoCloseable {
  
  	/**
  	 * The values for the config parameter submodule.<name>.ignore
  	 *
  	 * @since 3.6
  	 */
  	public enum IgnoreSubmoduleMode {
  		/**
  		 * Ignore all modifications to submodules
  		 */
  		ALL,
  
  		/**
  		 * Ignore changes to the working tree of a submodule
  		 */
  		DIRTY,
  
  		/**
 		 * Ignore changes to untracked files in the working tree of a submodule
 		 */
 		UNTRACKED,
 
 		/**
 		 * Ignore nothing. That's the default
 		 */
 		NONE;
 	}
 
 	/**
 	 * Create a generator to walk over the submodule entries currently in the
 	 * index
 	 *
 	 * The {@code .gitmodules} file is read from the index.
 	 *
 	 * @param repository
 	 *            a {@link org.eclipse.jgit.lib.Repository} object.
 	 * @return generator over submodule index entries. The caller is responsible
 	 *         for calling {@link #close()}.
 	 * @throws java.io.IOException
 	 */
 	public static SubmoduleWalk forIndex(Repository repository)
 			throws IOException {
 		@SuppressWarnings("resource") // The caller closes it
 		SubmoduleWalk generator = new SubmoduleWalk(repository);
 		try {
 			DirCache index = repository.readDirCache();
 			generator.setTree(new DirCacheIterator(index));
 		} catch (IOException e) {
 			generator.close();
 			throw e;
 		}
 		return generator;
 	}
 
 	/**
 	 * Create a generator and advance it to the submodule entry at the given
 	 * path
 	 *
 	 * @param repository
 	 *            a {@link org.eclipse.jgit.lib.Repository} object.
 	 * @param treeId
 	 *            the root of a tree containing both a submodule at the given
 	 *            path and .gitmodules at the root.
 	 * @param path
 	 *            a {@link java.lang.String} object.
 	 * @return generator at given path. The caller is responsible for calling
 	 *         {@link #close()}. Null if no submodule at given path.
 	 * @throws java.io.IOException
 	 */
 	public static SubmoduleWalk forPath(Repository repository,
 			AnyObjectId treeId, String path) throws IOException {
 		SubmoduleWalk generator = new SubmoduleWalk(repository);
 		try {
 			generator.setTree(treeId);
 			PathFilter filter = PathFilter.create(path);
 			generator.setFilter(filter);
 			generator.setRootTree(treeId);
 			while (generator.next())
 				if (filter.isDone(generator.walk))
 					return generator;
 		} catch (IOException e) {
 			generator.close();
 			throw e;
 		}
 		generator.close();
 		return null;
 	}
 
 	/**
 	 * Create a generator and advance it to the submodule entry at the given
 	 * path
 	 *
 	 * @param repository
 	 *            a {@link org.eclipse.jgit.lib.Repository} object.
 	 * @param iterator
 	 *            the root of a tree containing both a submodule at the given
 	 *            path and .gitmodules at the root.
 	 * @param path
 	 *            a {@link java.lang.String} object.
 	 * @return generator at given path. The caller is responsible for calling
 	 *         {@link #close()}. Null if no submodule at given path.
 	 * @throws java.io.IOException
 	 */
 	public static SubmoduleWalk forPath(Repository repository,
 			AbstractTreeIterator iterator, String path) throws IOException {
 		SubmoduleWalk generator = new SubmoduleWalk(repository);
 		try {
 			generator.setTree(iterator);
 			PathFilter filter = PathFilter.create(path);
 			generator.setFilter(filter);
 			generator.setRootTree(iterator);
 			while (generator.next())
 				if (filter.isDone(generator.walk))
 					return generator;
 		} catch (IOException e) {
 			generator.close();
 			throw e;
 		}
 		generator.close();
 		return null;
 	}
 
 	/**
 	 * Get submodule directory
 	 *
 	 * @param parent
 	 *            the {@link org.eclipse.jgit.lib.Repository}.
 	 * @param path
 	 *            submodule path
 	 * @return directory
 	 */
 	public static File getSubmoduleDirectory(final Repository parent,
 			final String path) {
 		return new File(parent.getWorkTree(), path);
 	}
 
 	/**
 	 * Get submodule repository
 	 *
 	 * @param parent
 	 *            the {@link org.eclipse.jgit.lib.Repository}.
 	 * @param path
 	 *            submodule path
 	 * @return repository or null if repository doesn't exist
 	 * @throws java.io.IOException
 	 */
 	public static Repository>Repository getSubmoduleRepository(final Repository parent,
 			final String path) throws IOException {
 		return getSubmoduleRepository(parent.getWorkTree(), path,
 				parent.getFS());
 	}
 
 	/**
 	 * Get submodule repository at path
 	 *
 	 * @param parent
 	 *            the parent
 	 * @param path
 	 *            submodule path
 	 * @return repository or null if repository doesn't exist
 	 * @throws java.io.IOException
 	 */
 	public static Repository getSubmoduleRepository(final File parent,
 			final String path) throws IOException {
 		return getSubmoduleRepository(parent, path, FS.DETECTED);
 	}
 
 	/**
 	 * Get submodule repository at path, using the specified file system
 	 * abstraction
 	 *
 	 * @param parent
 	 * @param path
 	 * @param fs
 	 *            the file system abstraction to be used
 	 * @return repository or null if repository doesn't exist
 	 * @throws IOException
 	 * @since 4.10
 	 */
 	public static Repository getSubmoduleRepository(final File parent,
 			final String path, FS fs) throws IOException {
 		File subWorkTree = new File(parent, path);
 		if (!subWorkTree.isDirectory())
 			return null;
 		File workTree = new File(parent, path);
 		try {
 			return new RepositoryBuilder() //
 					.setMustExist(true) //
 					.setFS(fs) //
 					.setWorkTree(workTree) //
 					.build();
 		} catch (RepositoryNotFoundException e) {
 			return null;
 		}
 	}
 
 	/**
 	 * Resolve submodule repository URL.
 	 * <p>
 	 * This handles relative URLs that are typically specified in the
 	 * '.gitmodules' file by resolving them against the remote URL of the parent
 	 * repository.
 	 * <p>
 	 * Relative URLs will be resolved against the parent repository's working
 	 * directory if the parent repository has no configured remote URL.
 	 *
 	 * @param parent
 	 *            parent repository
 	 * @param url
 	 *            absolute or relative URL of the submodule repository
 	 * @return resolved URL
 	 * @throws java.io.IOException
 	 */
 	public static String getSubmoduleRemoteUrl(final Repository parent,
 			final String url) throws IOException {
 		if (!url.startsWith("./") && !url.startsWith("../")) //$NON-NLS-1$ //$NON-NLS-2$
 			return url;
 
 		String remoteName = null;
 		// Look up remote URL associated wit HEAD ref
 		Ref ref = parent.exactRef(Constants.HEAD);
 		if (ref != null) {
 			if (ref.isSymbolic())
 				ref = ref.getLeaf();
 			remoteName = parent.getConfig().getString(
 					ConfigConstants.CONFIG_BRANCH_SECTION,
 					Repository.shortenRefName(ref.getName()),
 					ConfigConstants.CONFIG_KEY_REMOTE);
 		}
 
 		// Fall back to 'origin' if current HEAD ref has no remote URL
 		if (remoteName == null)
 			remoteName = Constants.DEFAULT_REMOTE_NAME;
 
 		String remoteUrl = parent.getConfig().getString(
 				ConfigConstants.CONFIG_REMOTE_SECTION, remoteName,
 				ConfigConstants.CONFIG_KEY_URL);
 
 		// Fall back to parent repository's working directory if no remote URL
 		if (remoteUrl == null) {
 			remoteUrl = parent.getWorkTree().getAbsolutePath();
 			// Normalize slashes to '/'
 			if ('\\' == File.separatorChar)
 				remoteUrl = remoteUrl.replace('\\', '/');
 		}
 
 		// Remove trailing '/'
 		if (remoteUrl.charAt(remoteUrl.length() - 1) == '/')
 			remoteUrl = remoteUrl.substring(0, remoteUrl.length() - 1);
 
 		char separator = '/';
 		String submoduleUrl = url;
 		while (submoduleUrl.length() > 0) {
 			if (submoduleUrl.startsWith("./")) //$NON-NLS-1$
 				submoduleUrl = submoduleUrl.substring(2);
 			else if (submoduleUrl.startsWith("../")) { //$NON-NLS-1$
 				int lastSeparator = remoteUrl.lastIndexOf('/');
 				if (lastSeparator < 1) {
 					lastSeparator = remoteUrl.lastIndexOf(':');
 					separator = ':';
 				}
 				if (lastSeparator < 1)
 					throw new IOException(MessageFormat.format(
 							JGitText.get().submoduleParentRemoteUrlInvalid,
 							remoteUrl));
 				remoteUrl = remoteUrl.substring(0, lastSeparator);
 				submoduleUrl = submoduleUrl.substring(3);
 			} else
 				break;
 		}
 		return remoteUrl + separator + submoduleUrl;
 	}
 
 	private final Repository repository;
 
 	private final TreeWalk walk;
 
 	private StoredConfig repoConfig;
 
 	private AbstractTreeIterator rootTree;
 
 	private Config modulesConfig;
 
 	private String path;
 
 	private Map<String, String> pathToName;
 
 	/**
 	 * Create submodule generator
 	 *
 	 * @param repository
 	 *            the {@link org.eclipse.jgit.lib.Repository}.
 	 * @throws java.io.IOException
 	 */
 	public SubmoduleWalk(Repository repository) throws IOException {
 		this.repository = repository;
 		repoConfig = repository.getConfig();
 		walk = new TreeWalk(repository);
 		walk.setRecursive(true);
 	}
 
 	/**
 	 * Set the config used by this walk.
 	 *
 	 * This method need only be called if constructing a walk manually instead of
 	 * with one of the static factory methods above.
 	 *
 	 * @param config
 	 *            .gitmodules config object
 	 * @return this generator
 	 */
 	public SubmoduleWalk setModulesConfig(Config config) {
 		modulesConfig = config;
 		loadPathNames();
 		return this;
 	}
 
 	/**
 	 * Set the tree used by this walk for finding {@code .gitmodules}.
 	 * <p>
 	 * The root tree is not read until the first submodule is encountered by the
 	 * walk.
 	 * <p>
 	 * This method need only be called if constructing a walk manually instead of
 	 * with one of the static factory methods above.
 	 *
 	 * @param tree
 	 *            tree containing .gitmodules
 	 * @return this generator
 	 */
 	public SubmoduleWalk setRootTree(AbstractTreeIterator tree) {
 		rootTree = tree;
 		modulesConfig = null;
 		pathToName = null;
 		return this;
 	}
 
 	/**
 	 * Set the tree used by this walk for finding {@code .gitmodules}.
 	 * <p>
 	 * The root tree is not read until the first submodule is encountered by the
 	 * walk.
 	 * <p>
 	 * This method need only be called if constructing a walk manually instead of
 	 * with one of the static factory methods above.
 	 *
 	 * @param id
 	 *            ID of a tree containing .gitmodules
 	 * @return this generator
 	 * @throws java.io.IOException
 	 */
 	public SubmoduleWalk setRootTree(AnyObjectId id) throws IOException {
 		final CanonicalTreeParserreeParser.html#CanonicalTreeParser">CanonicalTreeParser p = new CanonicalTreeParser();
 		p.reset(walk.getObjectReader(), id);
 		rootTree = p;
 		modulesConfig = null;
 		pathToName = null;
 		return this;
 	}
 
 	/**
 	 * Load the config for this walk from {@code .gitmodules}.
 	 * <p>
 	 * Uses the root tree if {@link #setRootTree(AbstractTreeIterator)} was
 	 * previously called, otherwise uses the working tree.
 	 * <p>
 	 * If no submodule config is found, loads an empty config.
 	 *
 	 * @return this generator
 	 * @throws java.io.IOException
 	 *             if an error occurred, or if the repository is bare
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 */
 	public SubmoduleWalk loadModulesConfig() throws IOException, ConfigInvalidException {
 		if (rootTree == null) {
 			File modulesFile = new File(repository.getWorkTree(),
 					Constants.DOT_GIT_MODULES);
 			FileBasedConfig config = new FileBasedConfig(modulesFile,
 					repository.getFS());
 			config.load();
 			modulesConfig = config;
 			loadPathNames();
 		} else {
 			try (TreeWalk.html#TreeWalk">TreeWalk configWalk = new TreeWalk(repository)) {
 				configWalk.addTree(rootTree);
 
 				// The root tree may be part of the submodule walk, so we need to revert
 				// it after this walk.
 				int idx;
 				for (idx = 0; !rootTree.first(); idx++) {
 					rootTree.back(1);
 				}
 
 				try {
 					configWalk.setRecursive(false);
 					PathFilter filter = PathFilter.create(Constants.DOT_GIT_MODULES);
 					configWalk.setFilter(filter);
 					while (configWalk.next()) {
 						if (filter.isDone(configWalk)) {
 							modulesConfig = new BlobBasedConfig(null, repository,
 									configWalk.getObjectId(0));
 							loadPathNames();
 							return this;
 						}
 					}
 					modulesConfig = new Config();
 					pathToName = null;
 				} finally {
 					if (idx > 0)
 						rootTree.next(idx);
 				}
 			}
 		}
 		return this;
 	}
 
 	private void loadPathNames() {
 		pathToName = null;
 		if (modulesConfig != null) {
 			HashMap<String, String> pathNames = new HashMap<>();
 			for (String name : modulesConfig
 					.getSubsections(ConfigConstants.CONFIG_SUBMODULE_SECTION)) {
 				pathNames.put(modulesConfig.getString(
 						ConfigConstants.CONFIG_SUBMODULE_SECTION, name,
 						ConfigConstants.CONFIG_KEY_PATH), name);
 			}
 			pathToName = pathNames;
 		}
 	}
 
 	/**
 	 * Checks whether the working tree contains a .gitmodules file. That's a
 	 * hint that the repo contains submodules.
 	 *
 	 * @param repository
 	 *            the repository to check
 	 * @return <code>true</code> if the working tree contains a .gitmodules file,
 	 *         <code>false</code> otherwise. Always returns <code>false</code>
 	 *         for bare repositories.
 	 * @throws java.io.IOException
 	 * @throws CorruptObjectException if any.
 	 * @since 3.6
 	 */
 	public static boolean containsGitModulesFile(Repository repository)
 			throws IOException {
 		if (repository.isBare()) {
 			return false;
 		}
 		File modulesFile = new File(repository.getWorkTree(),
 				Constants.DOT_GIT_MODULES);
 		return (modulesFile.exists());
 	}
 
 	private void lazyLoadModulesConfig() throws IOException, ConfigInvalidException {
 		if (modulesConfig == null) {
 			loadModulesConfig();
 		}
 	}
 
 	private String getModuleName(String modulePath) {
 		String name = pathToName != null ? pathToName.get(modulePath) : null;
 		return name != null ? name : modulePath;
 	}
 
 	/**
 	 * Set tree filter
 	 *
 	 * @param filter
 	 *            a {@link org.eclipse.jgit.treewalk.filter.TreeFilter} object.
 	 * @return this generator
 	 */
 	public SubmoduleWalk setFilter(TreeFilter filter) {
 		walk.setFilter(filter);
 		return this;
 	}
 
 	/**
 	 * Set the tree iterator used for finding submodule entries
 	 *
 	 * @param iterator
 	 *            an {@link org.eclipse.jgit.treewalk.AbstractTreeIterator}
 	 *            object.
 	 * @return this generator
 	 * @throws org.eclipse.jgit.errors.CorruptObjectException
 	 */
 	public SubmoduleWalk setTree(AbstractTreeIterator iterator)
 			throws CorruptObjectException {
 		walk.addTree(iterator);
 		return this;
 	}
 
 	/**
 	 * Set the tree used for finding submodule entries
 	 *
 	 * @param treeId
 	 *            an {@link org.eclipse.jgit.lib.AnyObjectId} object.
 	 * @return this generator
 	 * @throws java.io.IOException
 	 * @throws IncorrectObjectTypeException
 	 *             if any.
 	 * @throws MissingObjectException
 	 *             if any.
 	 */
 	public SubmoduleWalk setTree(AnyObjectId treeId) throws IOException {
 		walk.addTree(treeId);
 		return this;
 	}
 
 	/**
 	 * Reset generator and start new submodule walk
 	 *
 	 * @return this generator
 	 */
 	public SubmoduleWalk reset() {
 		repoConfig = repository.getConfig();
 		modulesConfig = null;
 		pathToName = null;
 		walk.reset();
 		return this;
 	}
 
 	/**
 	 * Get directory that will be the root of the submodule's local repository
 	 *
 	 * @return submodule repository directory
 	 */
 	public File getDirectory() {
 		return getSubmoduleDirectory(repository, path);
 	}
 
 	/**
 	 * Advance to next submodule in the index tree.
 	 *
 	 * The object id and path of the next entry can be obtained by calling
 	 * {@link #getObjectId()} and {@link #getPath()}.
 	 *
 	 * @return true if entry found, false otherwise
 	 * @throws java.io.IOException
 	 */
 	public boolean next() throws IOException {
 		while (walk.next()) {
 			if (FileMode.GITLINK != walk.getFileMode(0))
 				continue;
 			path = walk.getPathString();
 			return true;
 		}
 		path = null;
 		return false;
 	}
 
 	/**
 	 * Get path of current submodule entry
 	 *
 	 * @return path
 	 */
 	public String getPath() {
 		return path;
 	}
 
 	/**
 	 * The module name for the current submodule entry (used for the section name of .git/config)
 	 * @since 4.10
 	 * @return name
 	 */
 	public String getModuleName() {
 		return getModuleName(path);
 	}
 
 	/**
 	 * Get object id of current submodule entry
 	 *
 	 * @return object id
 	 */
 	public ObjectId getObjectId() {
 		return walk.getObjectId(0);
 	}
 
 	/**
 	 * Get the configured path for current entry. This will be the value from
 	 * the .gitmodules file in the current repository's working tree.
 	 *
 	 * @return configured path
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 * @throws java.io.IOException
 	 */
 	public String getModulesPath() throws IOException, ConfigInvalidException {
 		lazyLoadModulesConfig();
 		return modulesConfig.getString(ConfigConstants.CONFIG_SUBMODULE_SECTION,
 				getModuleName(), ConfigConstants.CONFIG_KEY_PATH);
 	}
 
 	/**
 	 * Get the configured remote URL for current entry. This will be the value
 	 * from the repository's config.
 	 *
 	 * @return configured URL
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 * @throws java.io.IOException
 	 */
 	public String getConfigUrl() throws IOException, ConfigInvalidException {
 		return repoConfig.getString(ConfigConstants.CONFIG_SUBMODULE_SECTION,
 				getModuleName(), ConfigConstants.CONFIG_KEY_URL);
 	}
 
 	/**
 	 * Get the configured remote URL for current entry. This will be the value
 	 * from the .gitmodules file in the current repository's working tree.
 	 *
 	 * @return configured URL
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 * @throws java.io.IOException
 	 */
 	public String getModulesUrl() throws IOException, ConfigInvalidException {
 		lazyLoadModulesConfig();
 		return modulesConfig.getString(ConfigConstants.CONFIG_SUBMODULE_SECTION,
 				getModuleName(), ConfigConstants.CONFIG_KEY_URL);
 	}
 
 	/**
 	 * Get the configured update field for current entry. This will be the value
 	 * from the repository's config.
 	 *
 	 * @return update value
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 * @throws java.io.IOException
 	 */
 	public String getConfigUpdate() throws IOException, ConfigInvalidException {
 		return repoConfig.getString(ConfigConstants.CONFIG_SUBMODULE_SECTION,
 				getModuleName(), ConfigConstants.CONFIG_KEY_UPDATE);
 	}
 
 	/**
 	 * Get the configured update field for current entry. This will be the value
 	 * from the .gitmodules file in the current repository's working tree.
 	 *
 	 * @return update value
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 * @throws java.io.IOException
 	 */
 	public String getModulesUpdate() throws IOException, ConfigInvalidException {
 		lazyLoadModulesConfig();
 		return modulesConfig.getString(ConfigConstants.CONFIG_SUBMODULE_SECTION,
 				getModuleName(), ConfigConstants.CONFIG_KEY_UPDATE);
 	}
 
 	/**
 	 * Get the configured ignore field for the current entry. This will be the
 	 * value from the .gitmodules file in the current repository's working tree.
 	 *
 	 * @return ignore value
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 * @throws java.io.IOException
 	 * @since 3.6
 	 */
 	public IgnoreSubmoduleMode getModulesIgnore() throws IOException,
 			ConfigInvalidException {
 		lazyLoadModulesConfig();
 		return modulesConfig.getEnum(IgnoreSubmoduleMode.values(),
 				ConfigConstants.CONFIG_SUBMODULE_SECTION, getModuleName(),
 				ConfigConstants.CONFIG_KEY_IGNORE, IgnoreSubmoduleMode.NONE);
 	}
 
 	/**
 	 * Get repository for current submodule entry
 	 *
 	 * @return repository or null if non-existent
 	 * @throws java.io.IOException
 	 */
 	public Repository getRepository() throws IOException {
 		return getSubmoduleRepository(repository, path);
 	}
 
 	/**
 	 * Get commit id that HEAD points to in the current submodule's repository
 	 *
 	 * @return object id of HEAD reference
 	 * @throws java.io.IOException
 	 */
 	public ObjectId getHead() throws IOException {
 		try (Repository subRepo = getRepository()) {
 			if (subRepo == null) {
 				return null;
 			}
 			return subRepo.resolve(Constants.HEAD);
 		}
 	}
 
 	/**
 	 * Get ref that HEAD points to in the current submodule's repository
 	 *
 	 * @return ref name, null on failures
 	 * @throws java.io.IOException
 	 */
 	public String getHeadRef() throws IOException {
 		try (Repository subRepo = getRepository()) {
 			if (subRepo == null) {
 				return null;
 			}
 			Ref head = subRepo.exactRef(Constants.HEAD);
 			return head != null ? head.getLeaf().getName() : null;
 		}
 	}
 
 	/**
 	 * Get the resolved remote URL for the current submodule.
 	 * <p>
 	 * This method resolves the value of {@link #getModulesUrl()} to an absolute
 	 * URL
 	 *
 	 * @return resolved remote URL
 	 * @throws java.io.IOException
 	 * @throws org.eclipse.jgit.errors.ConfigInvalidException
 	 */
 	public String getRemoteUrl() throws IOException, ConfigInvalidException {
 		String url = getModulesUrl();
 		return url != null ? getSubmoduleRemoteUrl(repository, url) : null;
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * <p>
 	 * Release any resources used by this walker's reader.
 	 *
 	 * @since 4.0
 	 */
 	@Override
 	public void close() {
 		walk.close();
 	}
 }