NAME

       gitrepository-layout - Git Repository Layout

SYNOPSIS

       $GIT_DIR/*

DESCRIPTION

       A Git repository comes in two different flavours:

       •   a .git directory at the root of the working tree;

       •   a <project>.git directory that is a bare repository (i.e. without its own working tree), that is
           typically used for exchanging histories with others by pushing into it and fetching from it.

       Note: Also you can have a plain text file .git at the root of your working tree, containing gitdir:
       <path> to point at the real directory that has the repository. This mechanism is often used for a working
       tree of a submodule checkout, to allow you in the containing superproject to git checkout a branch that
       does not have the submodule. The checkout has to remove the entire submodule working tree, without losing
       the submodule repository.

       These things may exist in a Git repository.

       objects
           Object store associated with this repository. Usually an object store is self sufficient (i.e. all
           the objects that are referred to by an object found in it are also found in it), but there are a few
           ways to violate it.

            1. You could have an incomplete but locally usable repository by creating a shallow clone. See git-
               clone(1).

            2. You could be using the objects/info/alternates or $GIT_ALTERNATE_OBJECT_DIRECTORIES mechanisms to
               borrow objects from other object stores. A repository with this kind of incomplete object store
               is not suitable to be published for use with dumb transports but otherwise is OK as long as
               objects/info/alternates points at the object stores it borrows from.

               This directory is ignored if $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/objects" will be used
               instead.

       objects/[0-9a-f][0-9a-f]
           A newly created object is stored in its own file. The objects are splayed over 256 subdirectories
           using the first two characters of the sha1 object name to keep the number of directory entries in
           objects itself to a manageable number. Objects found here are often called unpacked (or loose)
           objects.

       objects/pack
           Packs (files that store many objects in compressed form, along with index files to allow them to be
           randomly accessed) are found in this directory.

       objects/info
           Additional information about the object store is recorded in this directory.

       objects/info/packs
           This file is to help dumb transports discover what packs are available in this object store. Whenever
           a pack is added or removed, git update-server-info should be run to keep this file up to date if the
           repository is published for dumb transports.  git repack does this by default.

       objects/info/alternates
           This file records paths to alternate object stores that this object store borrows objects from, one
           pathname per line. Note that not only native Git tools use it locally, but the HTTP fetcher also
           tries to use it remotely; this will usually work if you have relative paths (relative to the object
           database, not to the repository!) in your alternates file, but it will not work if you use absolute
           paths unless the absolute path in filesystem and web URL is the same. See also
           objects/info/http-alternates.

       objects/info/http-alternates
           This file records URLs to alternate object stores that this object store borrows objects from, to be
           used when the repository is fetched over HTTP.

       refs
           References are stored in subdirectories of this directory. The git prune command knows to preserve
           objects reachable from refs found in this directory and its subdirectories. This directory is ignored
           (except refs/bisect, refs/rewritten and refs/worktree) if $GIT_COMMON_DIR is set and
           "$GIT_COMMON_DIR/refs" will be used instead.

       refs/heads/name
           records tip-of-the-tree commit objects of branch name

       refs/tags/name
           records any object name (not necessarily a commit object, or a tag object that points at a commit
           object).

       refs/remotes/name
           records tip-of-the-tree commit objects of branches copied from a remote repository.

       refs/replace/<obj-sha1>
           records the SHA-1 of the object that replaces <obj-sha1>. This is similar to info/grafts and is
           internally used and maintained by git-replace(1). Such refs can be exchanged between repositories
           while grafts are not.

       packed-refs
           records the same information as refs/heads/, refs/tags/, and friends record in a more efficient way.
           See git-pack-refs(1). This file is ignored if $GIT_COMMON_DIR is set and
           "$GIT_COMMON_DIR/packed-refs" will be used instead.

       HEAD
           A symref (see glossary) to the refs/heads/ namespace describing the currently active branch. It does
           not mean much if the repository is not associated with any working tree (i.e. a bare repository), but
           a valid Git repository must have the HEAD file; some porcelains may use it to guess the designated
           "default" branch of the repository (usually master). It is legal if the named branch name does not
           (yet) exist. In some legacy setups, it is a symbolic link instead of a symref that points at the
           current branch.

           HEAD can also record a specific commit directly, instead of being a symref to point at the current
           branch. Such a state is often called detached HEAD.  See git-checkout(1) for details.

       config
           Repository specific configuration file. This file is ignored if $GIT_COMMON_DIR is set and
           "$GIT_COMMON_DIR/config" will be used instead.

       config.worktree
           Working directory specific configuration file for the main working directory in multiple working
           directory setup (see git-worktree(1)).

       branches
           A slightly deprecated way to store shorthands to be used to specify a URL to git fetch, git pull and
           git push. A file can be stored as branches/<name> and then name can be given to these commands in
           place of repository argument. See the REMOTES section in git-fetch(1) for details. This mechanism is
           legacy and not likely to be found in modern repositories. This directory is ignored if
           $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/branches" will be used instead.

       hooks
           Hooks are customization scripts used by various Git commands. A handful of sample hooks are installed
           when git init is run, but all of them are disabled by default. To enable, the .sample suffix has to
           be removed from the filename by renaming. Read githooks(5) for more details about each hook. This
           directory is ignored if $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/hooks" will be used instead.

       common
           When multiple working trees are used, most of files in $GIT_DIR are per-worktree with a few known
           exceptions. All files under common however will be shared between all working trees.

       index
           The current index file for the repository. It is usually not found in a bare repository.

       sharedindex.<SHA-1>
           The shared index part, to be referenced by $GIT_DIR/index and other temporary index files. Only valid
           in split index mode.

       info
           Additional information about the repository is recorded in this directory. This directory is ignored
           if $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/info" will be used instead.

       info/refs
           This file helps dumb transports discover what refs are available in this repository. If the
           repository is published for dumb transports, this file should be regenerated by git
           update-server-info every time a tag or branch is created or modified. This is normally done from the
           hooks/update hook, which is run by the git-receive-pack command when you git push into the
           repository.

       info/grafts
           This file records fake commit ancestry information, to pretend the set of parents a commit has is
           different from how the commit was actually created. One record per line describes a commit and its
           fake parents by listing their 40-byte hexadecimal object names separated by a space and terminated by
           a newline.

           Note that the grafts mechanism is outdated and can lead to problems transferring objects between
           repositories; see git-replace(1) for a more flexible and robust system to do the same thing.

       info/exclude
           This file, by convention among Porcelains, stores the exclude pattern list.  .gitignore is the
           per-directory ignore file.  git status, git add, git rm and git clean look at it but the core Git
           commands do not look at it. See also: gitignore(5).

       info/attributes
           Defines which attributes to assign to a path, similar to per-directory .gitattributes files. See
           also: gitattributes(5).

       info/sparse-checkout
           This file stores sparse checkout patterns. See also: git-read-tree(1).

       remotes
           Stores shorthands for URL and default refnames for use when interacting with remote repositories via
           git fetch, git pull and git push commands. See the REMOTES section in git-fetch(1) for details. This
           mechanism is legacy and not likely to be found in modern repositories. This directory is ignored if
           $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/remotes" will be used instead.

       logs
           Records of changes made to refs are stored in this directory. See git-update-ref(1) for more
           information. This directory is ignored (except logs/HEAD) if $GIT_COMMON_DIR is set and
           "$GIT_COMMON_DIR/logs" will be used instead.

       logs/refs/heads/name
           Records all changes made to the branch tip named name.

       logs/refs/tags/name
           Records all changes made to the tag named name.

       shallow
           This is similar to info/grafts but is internally used and maintained by shallow clone mechanism. See
           --depth option to git-clone(1) and git-fetch(1). This file is ignored if $GIT_COMMON_DIR is set and
           "$GIT_COMMON_DIR/shallow" will be used instead.

       commondir
           If this file exists, $GIT_COMMON_DIR (see git(1)) will be set to the path specified in this file if
           it is not explicitly set. If the specified path is relative, it is relative to $GIT_DIR. The
           repository with commondir is incomplete without the repository pointed by "commondir".

       modules
           Contains the git-repositories of the submodules.

       worktrees
           Contains administrative data for linked working trees. Each subdirectory contains the working
           tree-related part of a linked working tree. This directory is ignored if $GIT_COMMON_DIR is set, in
           which case "$GIT_COMMON_DIR/worktrees" will be used instead.

       worktrees/<id>/gitdir
           A text file containing the absolute path back to the .git file that points to here. This is used to
           check if the linked repository has been manually removed and there is no need to keep this directory
           any more. The mtime of this file should be updated every time the linked repository is accessed.

       worktrees/<id>/locked
           If this file exists, the linked working tree may be on a portable device and not available. The
           presence of this file prevents worktrees/<id> from being pruned either automatically or manually by
           git worktree prune. The file may contain a string explaining why the repository is locked.

       worktrees/<id>/config.worktree
           Working directory specific configuration file.

GIT REPOSITORY FORMAT VERSIONS

       Every git repository is marked with a numeric version in the core.repositoryformatversion key of its
       config file. This version specifies the rules for operating on the on-disk repository data. An
       implementation of git which does not understand a particular version advertised by an on-disk repository
       MUST NOT operate on that repository; doing so risks not only producing wrong results, but actually losing
       data.

       Because of this rule, version bumps should be kept to an absolute minimum. Instead, we generally prefer
       these strategies:

       •   bumping format version numbers of individual data files (e.g., index, packfiles, etc). This restricts
           the incompatibilities only to those files.

       •   introducing new data that gracefully degrades when used by older clients (e.g., pack bitmap files are
           ignored by older clients, which simply do not take advantage of the optimization they provide).

       A whole-repository format version bump should only be part of a change that cannot be independently
       versioned. For instance, if one were to change the reachability rules for objects, or the rules for
       locking refs, that would require a bump of the repository format version.

       Note that this applies only to accessing the repository’s disk contents directly. An older client which
       understands only format 0 may still connect via git:// to a repository using format 1, as long as the
       server process understands format 1.

       The preferred strategy for rolling out a version bump (whether whole repository or for a single file) is
       to teach git to read the new format, and allow writing the new format with a config switch or command
       line option (for experimentation or for those who do not care about backwards compatibility with older
       gits). Then after a long period to allow the reading capability to become common, we may switch to
       writing the new format by default.

       The currently defined format versions are:

   Version 0
       This is the format defined by the initial version of git, including but not limited to the format of the
       repository directory, the repository configuration file, and the object and ref storage. Specifying the
       complete behavior of git is beyond the scope of this document.

   Version 1
       This format is identical to version 0, with the following exceptions:

        1. When reading the core.repositoryformatversion variable, a git implementation which supports version 1
           MUST also read any configuration keys found in the extensions section of the configuration file.

        2. If a version-1 repository specifies any extensions.*  keys that the running git has not implemented,
           the operation MUST NOT proceed. Similarly, if the value of any known key is not understood by the
           implementation, the operation MUST NOT proceed.

       Note that if no extensions are specified in the config file, then core.repositoryformatversion SHOULD be
       set to 0 (setting it to 1 provides no benefit, and makes the repository incompatible with older
       implementations of git).

       This document will serve as the master list for extensions. Any implementation wishing to define a new
       extension should make a note of it here, in order to claim the name.

       The defined extensions are:

       noop
           This extension does not change git’s behavior at all. It is useful only for testing format-1
           compatibility.

       preciousObjects
           When the config key extensions.preciousObjects is set to true, objects in the repository MUST NOT be
           deleted (e.g., by git-prune or git repack -d).

       partialClone
           When the config key extensions.partialClone is set, it indicates that the repo was created with a
           partial clone (or later performed a partial fetch) and that the remote may have omitted sending
           certain unwanted objects. Such a remote is called a "promisor remote" and it promises that all such
           omitted objects can be fetched from it in the future.

           The value of this key is the name of the promisor remote.

       worktreeConfig
           If set, by default "git config" reads from both "config" and "config.worktree" files from GIT_DIR in
           that order. In multiple working directory mode, "config" file is shared while "config.worktree" is
           per-working directory (i.e., it’s in GIT_COMMON_DIR/worktrees/<id>/config.worktree)

SEE ALSO

       git-init(1), git-clone(1), git-fetch(1), git-pack-refs(1), git-gc(1), git-checkout(1), gitglossary(7),
       The Git User’s Manual[1]

GIT

       Part of the git(1) suite

NOTES

        1. The Git User’s Manual
           file:///usr/share/doc/git/html/user-manual.html