checkout: split part of it to new command 'restore'

[thirdparty/git.git] / Documentation / git.txt

git(1)
======

NAME
----
git - the stupid content tracker


SYNOPSIS
--------
[verse]
'git' [--version] [--help] [-C <path>] [-c <name>=<value>]
    [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
    [-p|--paginate|-P|--no-pager] [--no-replace-objects] [--bare]
    [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
    [--super-prefix=<path>]
    <command> [<args>]

DESCRIPTION
-----------
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.

See linkgit:gittutorial[7] to get started, then see
linkgit:giteveryday[7] for a useful minimum set of
commands.  The link:user-manual.html[Git User's Manual] has a more
in-depth introduction.

After you mastered the basic concepts, you can come back to this
page to learn what commands Git offers.  You can learn more about
individual Git commands with "git help command".  linkgit:gitcli[7]
manual page gives you an overview of the command-line command syntax.

A formatted and hyperlinked copy of the latest Git documentation
can be viewed at `https://git.github.io/htmldocs/git.html`.


OPTIONS
-------
--version::
        Prints the Git suite version that the 'git' program came from.

--help::
        Prints the synopsis and a list of the most commonly used
        commands. If the option `--all` or `-a` is given then all
        available commands are printed. If a Git command is named this
        option will bring up the manual page for that command.
+
Other options are available to control how the manual page is
displayed. See linkgit:git-help[1] for more information,
because `git --help ...` is converted internally into `git
help ...`.

-C <path>::
        Run as if git was started in '<path>' instead of the current working
        directory.  When multiple `-C` options are given, each subsequent
        non-absolute `-C <path>` is interpreted relative to the preceding `-C
        <path>`.
+
This option affects options that expect path name like `--git-dir` and
`--work-tree` in that their interpretations of the path names would be
made relative to the working directory caused by the `-C` option. For
example the following invocations are equivalent:

    git --git-dir=a.git --work-tree=b -C c status
    git --git-dir=c/a.git --work-tree=c/b status

-c <name>=<value>::
        Pass a configuration parameter to the command. The value
        given will override values from configuration files.
        The <name> is expected in the same format as listed by
        'git config' (subkeys separated by dots).
+
Note that omitting the `=` in `git -c foo.bar ...` is allowed and sets
`foo.bar` to the boolean true value (just like `[foo]bar` would in a
config file). Including the equals but with an empty value (like `git -c
foo.bar= ...`) sets `foo.bar` to the empty string which `git config
--type=bool` will convert to `false`.

--exec-path[=<path>]::
        Path to wherever your core Git programs are installed.
        This can also be controlled by setting the GIT_EXEC_PATH
        environment variable. If no path is given, 'git' will print
        the current setting and then exit.

--html-path::
        Print the path, without trailing slash, where Git's HTML
        documentation is installed and exit.

--man-path::
        Print the manpath (see `man(1)`) for the man pages for
        this version of Git and exit.

--info-path::
        Print the path where the Info files documenting this
        version of Git are installed and exit.

-p::
--paginate::
        Pipe all output into 'less' (or if set, $PAGER) if standard
        output is a terminal.  This overrides the `pager.<cmd>`
        configuration options (see the "Configuration Mechanism" section
        below).

-P::
--no-pager::
        Do not pipe Git output into a pager.

--git-dir=<path>::
        Set the path to the repository. This can also be controlled by
        setting the `GIT_DIR` environment variable. It can be an absolute
        path or relative path to current working directory.

--work-tree=<path>::
        Set the path to the working tree. It can be an absolute path
        or a path relative to the current working directory.
        This can also be controlled by setting the GIT_WORK_TREE
        environment variable and the core.worktree configuration
        variable (see core.worktree in linkgit:git-config[1] for a
        more detailed discussion).

--namespace=<path>::
        Set the Git namespace.  See linkgit:gitnamespaces[7] for more
        details.  Equivalent to setting the `GIT_NAMESPACE` environment
        variable.

--super-prefix=<path>::
        Currently for internal use only.  Set a prefix which gives a path from
        above a repository down to its root.  One use is to give submodules
        context about the superproject that invoked it.

--bare::
        Treat the repository as a bare repository.  If GIT_DIR
        environment is not set, it is set to the current working
        directory.

--no-replace-objects::
        Do not use replacement refs to replace Git objects. See
        linkgit:git-replace[1] for more information.

--literal-pathspecs::
        Treat pathspecs literally (i.e. no globbing, no pathspec magic).
        This is equivalent to setting the `GIT_LITERAL_PATHSPECS` environment
        variable to `1`.

--glob-pathspecs::
        Add "glob" magic to all pathspec. This is equivalent to setting
        the `GIT_GLOB_PATHSPECS` environment variable to `1`. Disabling
        globbing on individual pathspecs can be done using pathspec
        magic ":(literal)"

--noglob-pathspecs::
        Add "literal" magic to all pathspec. This is equivalent to setting
        the `GIT_NOGLOB_PATHSPECS` environment variable to `1`. Enabling
        globbing on individual pathspecs can be done using pathspec
        magic ":(glob)"

--icase-pathspecs::
        Add "icase" magic to all pathspec. This is equivalent to setting
        the `GIT_ICASE_PATHSPECS` environment variable to `1`.

--no-optional-locks::
        Do not perform optional operations that require locks. This is
        equivalent to setting the `GIT_OPTIONAL_LOCKS` to `0`.

--list-cmds=group[,group...]::
        List commands by group. This is an internal/experimental
        option and may change or be removed in the future. Supported
        groups are: builtins, parseopt (builtin commands that use
        parse-options), main (all commands in libexec directory),
        others (all other commands in `$PATH` that have git- prefix),
        list-<category> (see categories in command-list.txt),
        nohelpers (exclude helper commands), alias and config
        (retrieve command list from config variable completion.commands)

GIT COMMANDS
------------

We divide Git into high level ("porcelain") commands and low level
("plumbing") commands.

High-level commands (porcelain)
-------------------------------

We separate the porcelain commands into the main commands and some
ancillary user utilities.

Main porcelain commands
~~~~~~~~~~~~~~~~~~~~~~~

include::cmds-mainporcelain.txt[]

Ancillary Commands
~~~~~~~~~~~~~~~~~~
Manipulators:

include::cmds-ancillarymanipulators.txt[]

Interrogators:

include::cmds-ancillaryinterrogators.txt[]


Interacting with Others
~~~~~~~~~~~~~~~~~~~~~~~

These commands are to interact with foreign SCM and with other
people via patch over e-mail.

include::cmds-foreignscminterface.txt[]

Reset, restore and revert
~~~~~~~~~~~~~~~~~~~~~~~~~
There are three commands with similar names: `git reset`,
`git restore` and `git revert`.

* linkgit:git-revert[1] is about making a new commit that reverts the
  changes made by other commits.

* linkgit:git-restore[1] is about restoring files in the working tree
  from either the index or another commit. This command does not
  update your branch. The command can also be used to restore files in
  the index from another commit.

* linkgit:git-reset[1] is about updating your branch, moving the tip
  in order to add or remove commits from the branch. This operation
  changes the commit history.
+
`git reset` can also be used to restore the index, overlapping with
`git restore`.


Low-level commands (plumbing)
-----------------------------

Although Git includes its
own porcelain layer, its low-level commands are sufficient to support
development of alternative porcelains.  Developers of such porcelains
might start by reading about linkgit:git-update-index[1] and
linkgit:git-read-tree[1].

The interface (input, output, set of options and the semantics)
to these low-level commands are meant to be a lot more stable
than Porcelain level commands, because these commands are
primarily for scripted use.  The interface to Porcelain commands
on the other hand are subject to change in order to improve the
end user experience.

The following description divides
the low-level commands into commands that manipulate objects (in
the repository, index, and working tree), commands that interrogate and
compare objects, and commands that move objects and references between
repositories.


Manipulation commands
~~~~~~~~~~~~~~~~~~~~~

include::cmds-plumbingmanipulators.txt[]


Interrogation commands
~~~~~~~~~~~~~~~~~~~~~~

include::cmds-plumbinginterrogators.txt[]

In general, the interrogate commands do not touch the files in
the working tree.


Synching repositories
~~~~~~~~~~~~~~~~~~~~~

include::cmds-synchingrepositories.txt[]

The following are helper commands used by the above; end users
typically do not use them directly.

include::cmds-synchelpers.txt[]


Internal helper commands
~~~~~~~~~~~~~~~~~~~~~~~~

These are internal helper commands used by other commands; end
users typically do not use them directly.

include::cmds-purehelpers.txt[]


Configuration Mechanism
-----------------------

Git uses a simple text format to store customizations that are per
repository and are per user.  Such a configuration file may look
like this:

------------
#
# A '#' or ';' character indicates a comment.
#

; core variables
[core]
        ; Don't trust file modes
        filemode = false

; user identity
[user]
        name = "Junio C Hamano"
        email = "gitster@pobox.com"

------------

Various commands read from the configuration file and adjust
their operation accordingly.  See linkgit:git-config[1] for a
list and more details about the configuration mechanism.


Identifier Terminology
----------------------
<object>::
        Indicates the object name for any type of object.

<blob>::
        Indicates a blob object name.

<tree>::
        Indicates a tree object name.

<commit>::
        Indicates a commit object name.

<tree-ish>::
        Indicates a tree, commit or tag object name.  A
        command that takes a <tree-ish> argument ultimately wants to
        operate on a <tree> object but automatically dereferences
        <commit> and <tag> objects that point at a <tree>.

<commit-ish>::
        Indicates a commit or tag object name.  A
        command that takes a <commit-ish> argument ultimately wants to
        operate on a <commit> object but automatically dereferences
        <tag> objects that point at a <commit>.

<type>::
        Indicates that an object type is required.
        Currently one of: `blob`, `tree`, `commit`, or `tag`.

<file>::
        Indicates a filename - almost always relative to the
        root of the tree structure `GIT_INDEX_FILE` describes.

Symbolic Identifiers
--------------------
Any Git command accepting any <object> can also use the following
symbolic notation:

HEAD::
        indicates the head of the current branch.

<tag>::
        a valid tag 'name'
        (i.e. a `refs/tags/<tag>` reference).

<head>::
        a valid head 'name'
        (i.e. a `refs/heads/<head>` reference).

For a more complete list of ways to spell object names, see
"SPECIFYING REVISIONS" section in linkgit:gitrevisions[7].


File/Directory Structure
------------------------

Please see the linkgit:gitrepository-layout[5] document.

Read linkgit:githooks[5] for more details about each hook.

Higher level SCMs may provide and manage additional information in the
`$GIT_DIR`.


Terminology
-----------
Please see linkgit:gitglossary[7].


Environment Variables
---------------------
Various Git commands use the following environment variables:

The Git Repository
~~~~~~~~~~~~~~~~~~
These environment variables apply to 'all' core Git commands. Nb: it
is worth noting that they may be used/overridden by SCMS sitting above
Git so take care if using a foreign front-end.

`GIT_INDEX_FILE`::
        This environment allows the specification of an alternate
        index file. If not specified, the default of `$GIT_DIR/index`
        is used.

`GIT_INDEX_VERSION`::
        This environment variable allows the specification of an index
        version for new repositories.  It won't affect existing index
        files.  By default index file version 2 or 3 is used. See
        linkgit:git-update-index[1] for more information.

`GIT_OBJECT_DIRECTORY`::
        If the object storage directory is specified via this
        environment variable then the sha1 directories are created
        underneath - otherwise the default `$GIT_DIR/objects`
        directory is used.

`GIT_ALTERNATE_OBJECT_DIRECTORIES`::
        Due to the immutable nature of Git objects, old objects can be
        archived into shared, read-only directories. This variable
        specifies a ":" separated (on Windows ";" separated) list
        of Git object directories which can be used to search for Git
        objects. New objects will not be written to these directories.
+
Entries that begin with `"` (double-quote) will be interpreted
as C-style quoted paths, removing leading and trailing
double-quotes and respecting backslash escapes. E.g., the value
`"path-with-\"-and-:-in-it":vanilla-path` has two paths:
`path-with-"-and-:-in-it` and `vanilla-path`.

`GIT_DIR`::
        If the `GIT_DIR` environment variable is set then it
        specifies a path to use instead of the default `.git`
        for the base of the repository.
        The `--git-dir` command-line option also sets this value.

`GIT_WORK_TREE`::
        Set the path to the root of the working tree.
        This can also be controlled by the `--work-tree` command-line
        option and the core.worktree configuration variable.

`GIT_NAMESPACE`::
        Set the Git namespace; see linkgit:gitnamespaces[7] for details.
        The `--namespace` command-line option also sets this value.

`GIT_CEILING_DIRECTORIES`::
        This should be a colon-separated list of absolute paths.  If
        set, it is a list of directories that Git should not chdir up
        into while looking for a repository directory (useful for
        excluding slow-loading network directories).  It will not
        exclude the current working directory or a GIT_DIR set on the
        command line or in the environment.  Normally, Git has to read
        the entries in this list and resolve any symlink that
        might be present in order to compare them with the current
        directory.  However, if even this access is slow, you
        can add an empty entry to the list to tell Git that the
        subsequent entries are not symlinks and needn't be resolved;
        e.g.,
        `GIT_CEILING_DIRECTORIES=/maybe/symlink::/very/slow/non/symlink`.

`GIT_DISCOVERY_ACROSS_FILESYSTEM`::
        When run in a directory that does not have ".git" repository
        directory, Git tries to find such a directory in the parent
        directories to find the top of the working tree, but by default it
        does not cross filesystem boundaries.  This environment variable
        can be set to true to tell Git not to stop at filesystem
        boundaries.  Like `GIT_CEILING_DIRECTORIES`, this will not affect
        an explicit repository directory set via `GIT_DIR` or on the
        command line.

`GIT_COMMON_DIR`::
        If this variable is set to a path, non-worktree files that are
        normally in $GIT_DIR will be taken from this path
        instead. Worktree-specific files such as HEAD or index are
        taken from $GIT_DIR. See linkgit:gitrepository-layout[5] and
        linkgit:git-worktree[1] for
        details. This variable has lower precedence than other path
        variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...

Git Commits
~~~~~~~~~~~
`GIT_AUTHOR_NAME`::
`GIT_AUTHOR_EMAIL`::
`GIT_AUTHOR_DATE`::
`GIT_COMMITTER_NAME`::
`GIT_COMMITTER_EMAIL`::
`GIT_COMMITTER_DATE`::
'EMAIL'::
        see linkgit:git-commit-tree[1]

Git Diffs
~~~~~~~~~
`GIT_DIFF_OPTS`::
        Only valid setting is "--unified=??" or "-u??" to set the
        number of context lines shown when a unified diff is created.
        This takes precedence over any "-U" or "--unified" option
        value passed on the Git diff command line.

`GIT_EXTERNAL_DIFF`::
        When the environment variable `GIT_EXTERNAL_DIFF` is set, the
        program named by it is called, instead of the diff invocation
        described above.  For a path that is added, removed, or modified,
        `GIT_EXTERNAL_DIFF` is called with 7 parameters:

        path old-file old-hex old-mode new-file new-hex new-mode
+
where:

        <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
                         contents of <old|new>,
        <old|new>-hex:: are the 40-hexdigit SHA-1 hashes,
        <old|new>-mode:: are the octal representation of the file modes.
+
The file parameters can point at the user's working file
(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
when a new file is added), or a temporary file (e.g. `old-file` in the
index).  `GIT_EXTERNAL_DIFF` should not worry about unlinking the
temporary file --- it is removed when `GIT_EXTERNAL_DIFF` exits.
+
For a path that is unmerged, `GIT_EXTERNAL_DIFF` is called with 1
parameter, <path>.
+
For each path `GIT_EXTERNAL_DIFF` is called, two environment variables,
`GIT_DIFF_PATH_COUNTER` and `GIT_DIFF_PATH_TOTAL` are set.

`GIT_DIFF_PATH_COUNTER`::
        A 1-based counter incremented by one for every path.

`GIT_DIFF_PATH_TOTAL`::
        The total number of paths.

other
~~~~~
`GIT_MERGE_VERBOSITY`::
        A number controlling the amount of output shown by
        the recursive merge strategy.  Overrides merge.verbosity.
        See linkgit:git-merge[1]

`GIT_PAGER`::
        This environment variable overrides `$PAGER`. If it is set
        to an empty string or to the value "cat", Git will not launch
        a pager.  See also the `core.pager` option in
        linkgit:git-config[1].

`GIT_EDITOR`::
        This environment variable overrides `$EDITOR` and `$VISUAL`.
        It is used by several Git commands when, on interactive mode,
        an editor is to be launched. See also linkgit:git-var[1]
        and the `core.editor` option in linkgit:git-config[1].

`GIT_SSH`::
`GIT_SSH_COMMAND`::
        If either of these environment variables is set then 'git fetch'
        and 'git push' will use the specified command instead of 'ssh'
        when they need to connect to a remote system.
        The command-line parameters passed to the configured command are
        determined by the ssh variant.  See `ssh.variant` option in
        linkgit:git-config[1] for details.

+
`$GIT_SSH_COMMAND` takes precedence over `$GIT_SSH`, and is interpreted
by the shell, which allows additional arguments to be included.
`$GIT_SSH` on the other hand must be just the path to a program
(which can be a wrapper shell script, if additional arguments are
needed).
+
Usually it is easier to configure any desired options through your
personal `.ssh/config` file.  Please consult your ssh documentation
for further details.

`GIT_SSH_VARIANT`::
        If this environment variable is set, it overrides Git's autodetection
        whether `GIT_SSH`/`GIT_SSH_COMMAND`/`core.sshCommand` refer to OpenSSH,
        plink or tortoiseplink. This variable overrides the config setting
        `ssh.variant` that serves the same purpose.

`GIT_ASKPASS`::
        If this environment variable is set, then Git commands which need to
        acquire passwords or passphrases (e.g. for HTTP or IMAP authentication)
        will call this program with a suitable prompt as command-line argument
        and read the password from its STDOUT. See also the `core.askPass`
        option in linkgit:git-config[1].

`GIT_TERMINAL_PROMPT`::
        If this environment variable is set to `0`, git will not prompt
        on the terminal (e.g., when asking for HTTP authentication).

`GIT_CONFIG_NOSYSTEM`::
        Whether to skip reading settings from the system-wide
        `$(prefix)/etc/gitconfig` file.  This environment variable can
        be used along with `$HOME` and `$XDG_CONFIG_HOME` to create a
        predictable environment for a picky script, or you can set it
        temporarily to avoid using a buggy `/etc/gitconfig` file while
        waiting for someone with sufficient permissions to fix it.

`GIT_FLUSH`::
        If this environment variable is set to "1", then commands such
        as 'git blame' (in incremental mode), 'git rev-list', 'git log',
        'git check-attr' and 'git check-ignore' will
        force a flush of the output stream after each record have been
        flushed. If this
        variable is set to "0", the output of these commands will be done
        using completely buffered I/O.   If this environment variable is
        not set, Git will choose buffered or record-oriented flushing
        based on whether stdout appears to be redirected to a file or not.

`GIT_TRACE`::
        Enables general trace messages, e.g. alias expansion, built-in
        command execution and external command execution.
+
If this variable is set to "1", "2" or "true" (comparison
is case insensitive), trace messages will be printed to
stderr.
+
If the variable is set to an integer value greater than 2
and lower than 10 (strictly) then Git will interpret this
value as an open file descriptor and will try to write the
trace messages into this file descriptor.
+
Alternatively, if the variable is set to an absolute path
(starting with a '/' character), Git will interpret this
as a file path and will try to append the trace messages
to it.
+
Unsetting the variable, or setting it to empty, "0" or
"false" (case insensitive) disables trace messages.

`GIT_TRACE_FSMONITOR`::
        Enables trace messages for the filesystem monitor extension.
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_PACK_ACCESS`::
        Enables trace messages for all accesses to any packs. For each
        access, the pack file name and an offset in the pack is
        recorded. This may be helpful for troubleshooting some
        pack-related performance problems.
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_PACKET`::
        Enables trace messages for all packets coming in or out of a
        given program. This can help with debugging object negotiation
        or other protocol issues. Tracing is turned off at a packet
        starting with "PACK" (but see `GIT_TRACE_PACKFILE` below).
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_PACKFILE`::
        Enables tracing of packfiles sent or received by a
        given program. Unlike other trace output, this trace is
        verbatim: no headers, and no quoting of binary data. You almost
        certainly want to direct into a file (e.g.,
        `GIT_TRACE_PACKFILE=/tmp/my.pack`) rather than displaying it on
        the terminal or mixing it with other trace output.
+
Note that this is currently only implemented for the client side
of clones and fetches.

`GIT_TRACE_PERFORMANCE`::
        Enables performance related trace messages, e.g. total execution
        time of each Git command.
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_SETUP`::
        Enables trace messages printing the .git, working tree and current
        working directory after Git has completed its setup phase.
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_SHALLOW`::
        Enables trace messages that can help debugging fetching /
        cloning of shallow repositories.
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_CURL`::
        Enables a curl full trace dump of all incoming and outgoing data,
        including descriptive information, of the git transport protocol.
        This is similar to doing curl `--trace-ascii` on the command line.
        This option overrides setting the `GIT_CURL_VERBOSE` environment
        variable.
        See `GIT_TRACE` for available trace output options.

`GIT_TRACE_CURL_NO_DATA`::
        When a curl trace is enabled (see `GIT_TRACE_CURL` above), do not dump
        data (that is, only dump info lines and headers).

`GIT_REDACT_COOKIES`::
        This can be set to a comma-separated list of strings. When a curl trace
        is enabled (see `GIT_TRACE_CURL` above), whenever a "Cookies:" header
        sent by the client is dumped, values of cookies whose key is in that
        list (case-sensitive) are redacted.

`GIT_LITERAL_PATHSPECS`::
        Setting this variable to `1` will cause Git to treat all
        pathspecs literally, rather than as glob patterns. For example,
        running `GIT_LITERAL_PATHSPECS=1 git log -- '*.c'` will search
        for commits that touch the path `*.c`, not any paths that the
        glob `*.c` matches. You might want this if you are feeding
        literal paths to Git (e.g., paths previously given to you by
        `git ls-tree`, `--raw` diff output, etc).

`GIT_GLOB_PATHSPECS`::
        Setting this variable to `1` will cause Git to treat all
        pathspecs as glob patterns (aka "glob" magic).

`GIT_NOGLOB_PATHSPECS`::
        Setting this variable to `1` will cause Git to treat all
        pathspecs as literal (aka "literal" magic).

`GIT_ICASE_PATHSPECS`::
        Setting this variable to `1` will cause Git to treat all
        pathspecs as case-insensitive.

`GIT_REFLOG_ACTION`::
        When a ref is updated, reflog entries are created to keep
        track of the reason why the ref was updated (which is
        typically the name of the high-level command that updated
        the ref), in addition to the old and new values of the ref.
        A scripted Porcelain command can use set_reflog_action
        helper function in `git-sh-setup` to set its name to this
        variable when it is invoked as the top level command by the
        end user, to be recorded in the body of the reflog.

`GIT_REF_PARANOIA`::
        If set to `1`, include broken or badly named refs when iterating
        over lists of refs. In a normal, non-corrupted repository, this
        does nothing. However, enabling it may help git to detect and
        abort some operations in the presence of broken refs. Git sets
        this variable automatically when performing destructive
        operations like linkgit:git-prune[1]. You should not need to set
        it yourself unless you want to be paranoid about making sure
        an operation has touched every ref (e.g., because you are
        cloning a repository to make a backup).

`GIT_ALLOW_PROTOCOL`::
        If set to a colon-separated list of protocols, behave as if
        `protocol.allow` is set to `never`, and each of the listed
        protocols has `protocol.<name>.allow` set to `always`
        (overriding any existing configuration). In other words, any
        protocol not mentioned will be disallowed (i.e., this is a
        whitelist, not a blacklist). See the description of
        `protocol.allow` in linkgit:git-config[1] for more details.

`GIT_PROTOCOL_FROM_USER`::
        Set to 0 to prevent protocols used by fetch/push/clone which are
        configured to the `user` state.  This is useful to restrict recursive
        submodule initialization from an untrusted repository or for programs
        which feed potentially-untrusted URLS to git commands.  See
        linkgit:git-config[1] for more details.

`GIT_PROTOCOL`::
        For internal use only.  Used in handshaking the wire protocol.
        Contains a colon ':' separated list of keys with optional values
        'key[=value]'.  Presence of unknown keys and values must be
        ignored.

`GIT_OPTIONAL_LOCKS`::
        If set to `0`, Git will complete any requested operation without
        performing any optional sub-operations that require taking a lock.
        For example, this will prevent `git status` from refreshing the
        index as a side effect. This is useful for processes running in
        the background which do not want to cause lock contention with
        other operations on the repository.  Defaults to `1`.

`GIT_REDIRECT_STDIN`::
`GIT_REDIRECT_STDOUT`::
`GIT_REDIRECT_STDERR`::
        Windows-only: allow redirecting the standard input/output/error
        handles to paths specified by the environment variables. This is
        particularly useful in multi-threaded applications where the
        canonical way to pass standard handles via `CreateProcess()` is
        not an option because it would require the handles to be marked
        inheritable (and consequently *every* spawned process would
        inherit them, possibly blocking regular Git operations). The
        primary intended use case is to use named pipes for communication
        (e.g. `\\.\pipe\my-git-stdin-123`).
+
Two special values are supported: `off` will simply close the
corresponding standard handle, and if `GIT_REDIRECT_STDERR` is
`2>&1`, standard error will be redirected to the same handle as
standard output.

`GIT_PRINT_SHA1_ELLIPSIS` (deprecated)::
        If set to `yes`, print an ellipsis following an
        (abbreviated) SHA-1 value.  This affects indications of
        detached HEADs (linkgit:git-checkout[1]) and the raw
        diff output (linkgit:git-diff[1]).  Printing an
        ellipsis in the cases mentioned is no longer considered
        adequate and support for it is likely to be removed in the
        foreseeable future (along with the variable).

Discussion[[Discussion]]
------------------------

More detail on the following is available from the
link:user-manual.html#git-concepts[Git concepts chapter of the
user-manual] and linkgit:gitcore-tutorial[7].

A Git project normally consists of a working directory with a ".git"
subdirectory at the top level.  The .git directory contains, among other
things, a compressed object database representing the complete history
of the project, an "index" file which links that history to the current
contents of the working tree, and named pointers into that history such
as tags and branch heads.

The object database contains objects of three main types: blobs, which
hold file data; trees, which point to blobs and other trees to build up
directory hierarchies; and commits, which each reference a single tree
and some number of parent commits.

The commit, equivalent to what other systems call a "changeset" or
"version", represents a step in the project's history, and each parent
represents an immediately preceding step.  Commits with more than one
parent represent merges of independent lines of development.

All objects are named by the SHA-1 hash of their contents, normally
written as a string of 40 hex digits.  Such names are globally unique.
The entire history leading up to a commit can be vouched for by signing
just that commit.  A fourth object type, the tag, is provided for this
purpose.

When first created, objects are stored in individual files, but for
efficiency may later be compressed together into "pack files".

Named pointers called refs mark interesting points in history.  A ref
may contain the SHA-1 name of an object or the name of another ref.  Refs
with names beginning `ref/head/` contain the SHA-1 name of the most
recent commit (or "head") of a branch under development.  SHA-1 names of
tags of interest are stored under `ref/tags/`.  A special ref named
`HEAD` contains the name of the currently checked-out branch.

The index file is initialized with a list of all paths and, for each
path, a blob object and a set of attributes.  The blob object represents
the contents of the file as of the head of the current branch.  The
attributes (last modified time, size, etc.) are taken from the
corresponding file in the working tree.  Subsequent changes to the
working tree can be found by comparing these attributes.  The index may
be updated with new content, and new commits may be created from the
content stored in the index.

The index is also capable of storing multiple entries (called "stages")
for a given pathname.  These stages are used to hold the various
unmerged version of a file when a merge is in progress.

FURTHER DOCUMENTATION
---------------------

See the references in the "description" section to get started
using Git.  The following is probably more detail than necessary
for a first-time user.

The link:user-manual.html#git-concepts[Git concepts chapter of the
user-manual] and linkgit:gitcore-tutorial[7] both provide
introductions to the underlying Git architecture.

See linkgit:gitworkflows[7] for an overview of recommended workflows.

See also the link:howto-index.html[howto] documents for some useful
examples.

The internals are documented in the
link:technical/api-index.html[Git API documentation].

Users migrating from CVS may also want to
read linkgit:gitcvs-migration[7].


Authors
-------
Git was started by Linus Torvalds, and is currently maintained by Junio
C Hamano. Numerous contributions have come from the Git mailing list
<git@vger.kernel.org>.  http://www.openhub.net/p/git/contributors/summary
gives you a more complete list of contributors.

If you have a clone of git.git itself, the
output of linkgit:git-shortlog[1] and linkgit:git-blame[1] can show you
the authors for specific parts of the project.

Reporting Bugs
--------------

Report bugs to the Git mailing list <git@vger.kernel.org> where the
development and maintenance is primarily done.  You do not have to be
subscribed to the list to send a message there.  See the list archive
at https://public-inbox.org/git for previous bug reports and other
discussions.

Issues which are security relevant should be disclosed privately to
the Git Security mailing list <git-security@googlegroups.com>.

SEE ALSO
--------
linkgit:gittutorial[7], linkgit:gittutorial-2[7],
linkgit:giteveryday[7], linkgit:gitcvs-migration[7],
linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
linkgit:gitworkflows[7]

GIT
---
Part of the linkgit:git[1] suite