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.
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:
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.
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" file 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)
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