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