/*
    * Copyright (C) 2008, Google Inc.
    * Copyright (C) 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
    * Copyright (C) 2006-2017, Shawn O. Pearce <spearce@spearce.org> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
   * SPDX-License-Identifier: BSD-3-Clause
   */
  
  package org.eclipse.jgit.lib;
  
  import static java.nio.charset.StandardCharsets.UTF_8;
  
  import java.nio.ByteBuffer;
  import java.nio.charset.Charset;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.text.MessageFormat;
  
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.util.MutableInteger;
  
  /**
   * Misc. constants and helpers used throughout JGit.
   */
  @SuppressWarnings("nls")
  public final class Constants {
  	/** Hash function used natively by Git for all objects. */
  	private static final String HASH_FUNCTION = "SHA-1";
  
  	/**
  	 * A Git object hash is 160 bits, i.e. 20 bytes.
  	 * <p>
  	 * Changing this assumption is not going to be as easy as changing this
  	 * declaration.
  	 */
  	public static final int OBJECT_ID_LENGTH = 20;
  
  	/**
  	 * A Git object can be expressed as a 40 character string of hexadecimal
  	 * digits.
  	 *
  	 * @see #OBJECT_ID_LENGTH
  	 */
  	public static final int OBJECT_ID_STRING_LENGTH = OBJECT_ID_LENGTH * 2;
  
  	/** Special name for the "HEAD" symbolic-ref. */
  	public static final String HEAD = "HEAD";
  
  	/** Special name for the "FETCH_HEAD" symbolic-ref. */
  	public static final String FETCH_HEAD = "FETCH_HEAD";
  
  	/**
  	 * Text string that identifies an object as a commit.
  	 * <p>
  	 * Commits connect trees into a string of project histories, where each
  	 * commit is an assertion that the best way to continue is to use this other
  	 * tree (set of files).
  	 */
  	public static final String TYPE_COMMIT = "commit";
  
  	/**
  	 * Text string that identifies an object as a blob.
  	 * <p>
  	 * Blobs store whole file revisions. They are used for any user file, as
  	 * well as for symlinks. Blobs form the bulk of any project's storage space.
  	 */
  	public static final String TYPE_BLOB = "blob";
  
  	/**
  	 * Text string that identifies an object as a tree.
  	 * <p>
  	 * Trees attach object ids (hashes) to names and file modes. The normal use
  	 * for a tree is to store a version of a directory and its contents.
  	 */
  	public static final String TYPE_TREE = "tree";
  
  	/**
  	 * Text string that identifies an object as an annotated tag.
  	 * <p>
  	 * Annotated tags store a pointer to any other object, and an additional
  	 * message. It is most commonly used to record a stable release of the
  	 * project.
  	 */
  	public static final String TYPE_TAG = "tag";
  
  	private static final byte[] ENCODED_TYPE_COMMIT = encodeASCII(TYPE_COMMIT);
  
  	private static final byte[] ENCODED_TYPE_BLOB = encodeASCII(TYPE_BLOB);
  
  	private static final byte[] ENCODED_TYPE_TREE = encodeASCII(TYPE_TREE);
  
  	private static final byte[] ENCODED_TYPE_TAG = encodeASCII(TYPE_TAG);
  
  	/** An unknown or invalid object type code. */
 	public static final int OBJ_BAD = -1;
 
 	/**
 	 * In-pack object type: extended types.
 	 * <p>
 	 * This header code is reserved for future expansion. It is currently
 	 * undefined/unsupported.
 	 */
 	public static final int OBJ_EXT = 0;
 
 	/**
 	 * In-pack object type: commit.
 	 * <p>
 	 * Indicates the associated object is a commit.
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 *
 	 * @see #TYPE_COMMIT
 	 */
 	public static final int OBJ_COMMIT = 1;
 
 	/**
 	 * In-pack object type: tree.
 	 * <p>
 	 * Indicates the associated object is a tree.
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 *
 	 * @see #TYPE_BLOB
 	 */
 	public static final int OBJ_TREE = 2;
 
 	/**
 	 * In-pack object type: blob.
 	 * <p>
 	 * Indicates the associated object is a blob.
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 *
 	 * @see #TYPE_BLOB
 	 */
 	public static final int OBJ_BLOB = 3;
 
 	/**
 	 * In-pack object type: annotated tag.
 	 * <p>
 	 * Indicates the associated object is an annotated tag.
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 *
 	 * @see #TYPE_TAG
 	 */
 	public static final int OBJ_TAG = 4;
 
 	/** In-pack object type: reserved for future use. */
 	public static final int OBJ_TYPE_5 = 5;
 
 	/**
 	 * In-pack object type: offset delta
 	 * <p>
 	 * Objects stored with this type actually have a different type which must
 	 * be obtained from their delta base object. Delta objects store only the
 	 * changes needed to apply to the base object in order to recover the
 	 * original object.
 	 * <p>
 	 * An offset delta uses a negative offset from the start of this object to
 	 * refer to its delta base. The base object must exist in this packfile
 	 * (even in the case of a thin pack).
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 */
 	public static final int OBJ_OFS_DELTA = 6;
 
 	/**
 	 * In-pack object type: reference delta
 	 * <p>
 	 * Objects stored with this type actually have a different type which must
 	 * be obtained from their delta base object. Delta objects store only the
 	 * changes needed to apply to the base object in order to recover the
 	 * original object.
 	 * <p>
 	 * A reference delta uses a full object id (hash) to reference the delta
 	 * base. The base object is allowed to be omitted from the packfile, but
 	 * only in the case of a thin pack being transferred over the network.
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 */
 	public static final int OBJ_REF_DELTA = 7;
 
 	/**
 	 * Pack file signature that occurs at file header - identifies file as Git
 	 * packfile formatted.
 	 * <p>
 	 * <b>This constant is fixed and is defined by the Git packfile format.</b>
 	 */
 	public static final byte[] PACK_SIGNATURE = { 'P', 'A', 'C', 'K' };
 
 	/**
 	 * Native character encoding for commit messages, file names...
 	 *
 	 * @deprecated Use {@link java.nio.charset.StandardCharsets#UTF_8} directly
 	 *             instead.
 	 */
 	@Deprecated
 	public static final Charset CHARSET;
 
 	/**
 	 * Native character encoding for commit messages, file names...
 	 *
 	 * @deprecated Use {@link java.nio.charset.StandardCharsets#UTF_8} directly
 	 *             instead.
 	 */
 	@Deprecated
 	public static final String CHARACTER_ENCODING;
 
 	/** Default main branch name */
 	public static final String MASTER = "master";
 
 	/** Default stash branch name */
 	public static final String STASH = "stash";
 
 	/** Prefix for branch refs */
 	public static final String R_HEADS = "refs/heads/";
 
 	/** Prefix for remotes refs */
 	public static final String R_REMOTES = "refs/remotes/";
 
 	/** Prefix for tag refs */
 	public static final String R_TAGS = "refs/tags/";
 
 	/** Prefix for notes refs */
 	public static final String R_NOTES = "refs/notes/";
 
 	/** Standard notes ref */
 	public static final String R_NOTES_COMMITS = R_NOTES + "commits";
 
 	/** Prefix for any ref */
 	public static final String R_REFS = "refs/";
 
 	/** Standard stash ref */
 	public static final String R_STASH = R_REFS + STASH;
 
 	/** Logs folder name */
 	public static final String LOGS = "logs";
 
 	/**
 	 * Objects folder name
 	 * @since 5.5
 	 */
 	public static final String OBJECTS = "objects";
 
 	/**
 	 * Reftable folder name
 	 * @since 5.6
 	 */
 	public static final String REFTABLE = "reftable";
 
 	/**
 	 * Reftable table list name.
 	 * @since 5.6.2
 	 */
 	public static final String TABLES_LIST = "tables.list";
 
 	/** Info refs folder */
 	public static final String INFO_REFS = "info/refs";
 
 	/**
 	 * Info alternates file (goes under OBJECTS)
 	 * @since 5.5
 	 */
 	public static final String INFO_ALTERNATES = "info/alternates";
 
 	/**
 	 * HTTP alternates file (goes under OBJECTS)
 	 * @since 5.5
 	 */
 	public static final String INFO_HTTP_ALTERNATES = "info/http-alternates";
 
 	/** Packed refs file */
 	public static final String PACKED_REFS = "packed-refs";
 
 	/**
 	 * Excludes-file
 	 *
 	 * @since 3.0
 	 */
 	public static final String INFO_EXCLUDE = "info/exclude";
 
 	/**
 	 * Attributes-override-file
 	 *
 	 * @since 4.2
 	 */
 	public static final String INFO_ATTRIBUTES = "info/attributes";
 
 	/**
 	 * The system property that contains the system user name
 	 *
 	 * @since 3.6
 	 */
 	public static final String OS_USER_DIR = "user.dir";
 
 	/** The system property that contains the system user name */
 	public static final String OS_USER_NAME_KEY = "user.name";
 
 	/** The environment variable that contains the author's name */
 	public static final String GIT_AUTHOR_NAME_KEY = "GIT_AUTHOR_NAME";
 
 	/** The environment variable that contains the author's email */
 	public static final String GIT_AUTHOR_EMAIL_KEY = "GIT_AUTHOR_EMAIL";
 
 	/** The environment variable that contains the commiter's name */
 	public static final String GIT_COMMITTER_NAME_KEY = "GIT_COMMITTER_NAME";
 
 	/** The environment variable that contains the commiter's email */
 	public static final String GIT_COMMITTER_EMAIL_KEY = "GIT_COMMITTER_EMAIL";
 
 	/**
 	 * The environment variable that blocks use of the system config file
 	 *
 	 * @since 3.3
 	 */
 	public static final String GIT_CONFIG_NOSYSTEM_KEY = "GIT_CONFIG_NOSYSTEM";
 
 	/**
 	 * The key of the XDG_CONFIG_HOME directory defined in the XDG base
 	 * directory specification, see
 	 * {@link "https://wiki.archlinux.org/index.php/XDG_Base_Directory"}
 	 *
 	 * @since 5.5.2
 	 */
 	public static final String XDG_CONFIG_HOME = "XDG_CONFIG_HOME";
 
 	/**
 	 * The environment variable that limits how close to the root of the file
 	 * systems JGit will traverse when looking for a repository root.
 	 */
 	public static final String GIT_CEILING_DIRECTORIES_KEY = "GIT_CEILING_DIRECTORIES";
 
 	/**
 	 * The environment variable that tells us which directory is the ".git"
 	 * directory
 	 */
 	public static final String GIT_DIR_KEY = "GIT_DIR";
 
 	/**
 	 * The environment variable that tells us which directory is the working
 	 * directory.
 	 */
 	public static final String GIT_WORK_TREE_KEY = "GIT_WORK_TREE";
 
 	/**
 	 * The environment variable that tells us which file holds the Git index.
 	 */
 	public static final String GIT_INDEX_FILE_KEY = "GIT_INDEX_FILE";
 
 	/**
 	 * The environment variable that tells us where objects are stored
 	 */
 	public static final String GIT_OBJECT_DIRECTORY_KEY = "GIT_OBJECT_DIRECTORY";
 
 	/**
 	 * The environment variable that tells us where to look for objects, besides
 	 * the default objects directory.
 	 */
 	public static final String GIT_ALTERNATE_OBJECT_DIRECTORIES_KEY = "GIT_ALTERNATE_OBJECT_DIRECTORIES";
 
 	/** Default value for the user name if no other information is available */
 	public static final String UNKNOWN_USER_DEFAULT = "unknown-user";
 
 	/** Beginning of the common "Signed-off-by: " commit message line */
 	public static final String SIGNED_OFF_BY_TAG = "Signed-off-by: ";
 
 	/** A gitignore file name */
 	public static final String GITIGNORE_FILENAME = ".gitignore";
 
 	/** Default remote name used by clone, push and fetch operations */
 	public static final String DEFAULT_REMOTE_NAME = "origin";
 
 	/** Default name for the Git repository directory */
 	public static final String DOT_GIT = ".git";
 
 	/** Default name for the Git repository configuration */
 	public static final String CONFIG = "config";
 
 	/** A bare repository typically ends with this string */
 	public static final String DOT_GIT_EXT = ".git";
 
 	/**
 	 * The default extension for local bundle files
 	 *
 	 * @since 5.8
 	 */
 	public static final String DOT_BUNDLE_EXT = ".bundle";
 
 	/**
 	 * Name of the attributes file
 	 *
 	 * @since 3.7
 	 */
 	public static final String DOT_GIT_ATTRIBUTES = ".gitattributes";
 
 	/**
 	 * Key for filters in .gitattributes
 	 *
 	 * @since 4.2
 	 */
 	public static final String ATTR_FILTER = "filter";
 
 	/**
 	 * clean command name, used to call filter driver
 	 *
 	 * @since 4.2
 	 */
 	public static final String ATTR_FILTER_TYPE_CLEAN = "clean";
 
 	/**
 	 * smudge command name, used to call filter driver
 	 *
 	 * @since 4.2
 	 */
 	public static final String ATTR_FILTER_TYPE_SMUDGE = "smudge";
 
 	/**
 	 * Builtin filter commands start with this prefix
 	 *
 	 * @since 4.6
 	 */
 	public static final String BUILTIN_FILTER_PREFIX = "jgit://builtin/";
 
 	/** Name of the ignore file */
 	public static final String DOT_GIT_IGNORE = ".gitignore";
 
 	/** Name of the submodules file */
 	public static final String DOT_GIT_MODULES = ".gitmodules";
 
 	/** Name of the .git/shallow file */
 	public static final String SHALLOW = "shallow";
 
 	/**
 	 * Prefix of the first line in a ".git" file
 	 *
 	 * @since 3.6
 	 */
 	public static final String GITDIR = "gitdir: ";
 
 	/**
 	 * Name of the folder (inside gitDir) where submodules are stored
 	 *
 	 * @since 3.6
 	 */
 	public static final String MODULES = "modules";
 
 	/**
 	 * Name of the folder (inside gitDir) where the hooks are stored.
 	 *
 	 * @since 3.7
 	 */
 	public static final String HOOKS = "hooks";
 
 	/**
 	 * Merge attribute.
 	 *
 	 * @since 4.9
 	 */
 	public static final String ATTR_MERGE = "merge"; //$NON-NLS-1$
 
 	/**
 	 * Diff attribute.
 	 *
 	 * @since 4.11
 	 */
 	public static final String ATTR_DIFF = "diff"; //$NON-NLS-1$
 
 	/**
 	 * Binary value for custom merger.
 	 *
 	 * @since 4.9
 	 */
 	public static final String ATTR_BUILTIN_BINARY_MERGER = "binary"; //$NON-NLS-1$
 
 	/**
 	 * Create a new digest function for objects.
 	 *
 	 * @return a new digest object.
 	 * @throws java.lang.RuntimeException
 	 *             this Java virtual machine does not support the required hash
 	 *             function. Very unlikely given that JGit uses a hash function
 	 *             that is in the Java reference specification.
 	 */
 	public static MessageDigest newMessageDigest() {
 		try {
 			return MessageDigest.getInstance(HASH_FUNCTION);
 		} catch (NoSuchAlgorithmException nsae) {
 			throw new RuntimeException(MessageFormat.format(
 					JGitText.get().requiredHashFunctionNotAvailable, HASH_FUNCTION), nsae);
 		}
 	}
 
 	/**
 	 * Convert an OBJ_* type constant to a TYPE_* type constant.
 	 *
 	 * @param typeCode the type code, from a pack representation.
 	 * @return the canonical string name of this type.
 	 */
 	public static String typeString(int typeCode) {
 		switch (typeCode) {
 		case OBJ_COMMIT:
 			return TYPE_COMMIT;
 		case OBJ_TREE:
 			return TYPE_TREE;
 		case OBJ_BLOB:
 			return TYPE_BLOB;
 		case OBJ_TAG:
 			return TYPE_TAG;
 		default:
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().badObjectType, Integer.valueOf(typeCode)));
 		}
 	}
 
 	/**
 	 * Convert an OBJ_* type constant to an ASCII encoded string constant.
 	 * <p>
 	 * The ASCII encoded string is often the canonical representation of
 	 * the type within a loose object header, or within a tag header.
 	 *
 	 * @param typeCode the type code, from a pack representation.
 	 * @return the canonical ASCII encoded name of this type.
 	 */
 	public static byte[] encodedTypeString(int typeCode) {
 		switch (typeCode) {
 		case OBJ_COMMIT:
 			return ENCODED_TYPE_COMMIT;
 		case OBJ_TREE:
 			return ENCODED_TYPE_TREE;
 		case OBJ_BLOB:
 			return ENCODED_TYPE_BLOB;
 		case OBJ_TAG:
 			return ENCODED_TYPE_TAG;
 		default:
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().badObjectType, Integer.valueOf(typeCode)));
 		}
 	}
 
 	/**
 	 * Parse an encoded type string into a type constant.
 	 *
 	 * @param id
 	 *            object id this type string came from; may be null if that is
 	 *            not known at the time the parse is occurring.
 	 * @param typeString
 	 *            string version of the type code.
 	 * @param endMark
 	 *            character immediately following the type string. Usually ' '
 	 *            (space) or '\n' (line feed).
 	 * @param offset
 	 *            position within <code>typeString</code> where the parse
 	 *            should start. Updated with the new position (just past
 	 *            <code>endMark</code> when the parse is successful.
 	 * @return a type code constant (one of {@link #OBJ_BLOB},
 	 *         {@link #OBJ_COMMIT}, {@link #OBJ_TAG}, {@link #OBJ_TREE}.
 	 * @throws org.eclipse.jgit.errors.CorruptObjectException
 	 *             there is no valid type identified by <code>typeString</code>.
 	 */
 	public static int decodeTypeString(final AnyObjectId id,
 			final byte[] typeString, final byte endMark,
 			final MutableInteger offset) throws CorruptObjectException {
 		try {
 			int position = offset.value;
 			switch (typeString[position]) {
 			case 'b':
 				if (typeString[position + 1] != 'l'
 						|| typeString[position + 2] != 'o'
 						|| typeString[position + 3] != 'b'
 						|| typeString[position + 4] != endMark)
 					throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
 				offset.value = position + 5;
 				return Constants.OBJ_BLOB;
 
 			case 'c':
 				if (typeString[position + 1] != 'o'
 						|| typeString[position + 2] != 'm'
 						|| typeString[position + 3] != 'm'
 						|| typeString[position + 4] != 'i'
 						|| typeString[position + 5] != 't'
 						|| typeString[position + 6] != endMark)
 					throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
 				offset.value = position + 7;
 				return Constants.OBJ_COMMIT;
 
 			case 't':
 				switch (typeString[position + 1]) {
 				case 'a':
 					if (typeString[position + 2] != 'g'
 							|| typeString[position + 3] != endMark)
 						throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
 					offset.value = position + 4;
 					return Constants.OBJ_TAG;
 
 				case 'r':
 					if (typeString[position + 2] != 'e'
 							|| typeString[position + 3] != 'e'
 							|| typeString[position + 4] != endMark)
 						throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
 					offset.value = position + 5;
 					return Constants.OBJ_TREE;
 
 				default:
 					throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
 				}
 
 			default:
 				throw new CorruptObjectException(id, JGitText.get().corruptObjectInvalidType);
 			}
 		} catch (ArrayIndexOutOfBoundsException bad) {
 			CorruptObjectException coe = new CorruptObjectException(id,
 					JGitText.get().corruptObjectInvalidType);
 			coe.initCause(bad);
 			throw coe;
 		}
 	}
 
 	/**
 	 * Convert an integer into its decimal representation.
 	 *
 	 * @param s
 	 *            the integer to convert.
 	 * @return a decimal representation of the input integer. The returned array
 	 *         is the smallest array that will hold the value.
 	 */
 	public static byte[] encodeASCII(long s) {
 		return encodeASCII(Long.toString(s));
 	}
 
 	/**
 	 * Convert a string to US-ASCII encoding.
 	 *
 	 * @param s
 	 *            the string to convert. Must not contain any characters over
 	 *            127 (outside of 7-bit ASCII).
 	 * @return a byte array of the same length as the input string, holding the
 	 *         same characters, in the same order.
 	 * @throws java.lang.IllegalArgumentException
 	 *             the input string contains one or more characters outside of
 	 *             the 7-bit ASCII character space.
 	 */
 	public static byte[] encodeASCII(String s) {
 		final byte[] r = new byte[s.length()];
 		for (int k = r.length - 1; k >= 0; k--) {
 			final char c = s.charAt(k);
 			if (c > 127)
 				throw new IllegalArgumentException(MessageFormat.format(JGitText.get().notASCIIString, s));
 			r[k] = (byte) c;
 		}
 		return r;
 	}
 
 	/**
 	 * Convert a string to a byte array in the standard character encoding.
 	 *
 	 * @param str
 	 *            the string to convert. May contain any Unicode characters.
 	 * @return a byte array representing the requested string, encoded using the
 	 *         default character encoding (UTF-8).
 	 * @see #CHARACTER_ENCODING
 	 */
 	public static byte[] encode(String str) {
 		final ByteBuffer bb = UTF_8.encode(str);
 		final int len = bb.limit();
 		if (bb.hasArray() && bb.arrayOffset() == 0) {
 			final byte[] arr = bb.array();
 			if (arr.length == len)
 				return arr;
 		}
 
 		final byte[] arr = new byte[len];
 		bb.get(arr);
 		return arr;
 	}
 
 	static {
 		if (OBJECT_ID_LENGTH != newMessageDigest().getDigestLength())
 			throw new LinkageError(JGitText.get().incorrectOBJECT_ID_LENGTH);
 		CHARSET = UTF_8;
 		CHARACTER_ENCODING = UTF_8.name();
 	}
 
 	/** name of the file containing the commit msg for a merge commit */
 	public static final String MERGE_MSG = "MERGE_MSG";
 
 	/** name of the file containing the IDs of the parents of a merge commit */
 	public static final String MERGE_HEAD = "MERGE_HEAD";
 
 	/** name of the file containing the ID of a cherry pick commit in case of conflicts */
 	public static final String CHERRY_PICK_HEAD = "CHERRY_PICK_HEAD";
 
 	/** name of the file containing the commit msg for a squash commit */
 	public static final String SQUASH_MSG = "SQUASH_MSG";
 
 	/** name of the file containing the ID of a revert commit in case of conflicts */
 	public static final String REVERT_HEAD = "REVERT_HEAD";
 
 	/**
 	 * name of the ref ORIG_HEAD used by certain commands to store the original
 	 * value of HEAD
 	 */
 	public static final String ORIG_HEAD = "ORIG_HEAD";
 
 	/**
 	 * Name of the file in which git commands and hooks store and read the
 	 * message prepared for the upcoming commit.
 	 *
 	 * @since 4.0
 	 */
 	public static final String COMMIT_EDITMSG = "COMMIT_EDITMSG";
 
 	/**
 	 * Well-known object ID for the empty blob.
 	 *
 	 * @since 0.9.1
 	 */
 	public static final ObjectId/../org/eclipse/jgit/lib/ObjectId.html#ObjectId">ObjectId EMPTY_BLOB_ID = ObjectId
 			.fromString("e69de29bb2d1d6434b8b29ae775ad8c2e48c5391");
 
 	/**
 	 * Well-known object ID for the empty tree.
 	 *
 	 * @since 5.1
 	 */
 	public static final ObjectId/../org/eclipse/jgit/lib/ObjectId.html#ObjectId">ObjectId EMPTY_TREE_ID = ObjectId
 			.fromString("4b825dc642cb6eb9a060e54bf8d69288fbee4904");
 
 	/**
 	 * Suffix of lock file name
 	 *
 	 * @since 4.7
 	 */
 	public static final String LOCK_SUFFIX = ".lock"; //$NON-NLS-1$
 
 	private Constants() {
 		// Hide the default constructor
 	}
 }