Documentation / git.txton commit Merge branch 'dp/read-not-mmap-small-loose-object' (7237f97)
   1git(1)
   2======
   3
   4NAME
   5----
   6git - the stupid content tracker
   7
   8
   9SYNOPSIS
  10--------
  11[verse]
  12'git' [--version] [--exec-path[=GIT_EXEC_PATH]] [--html-path]
  13    [-p|--paginate|--no-pager] [--no-replace-objects]
  14    [--bare] [--git-dir=GIT_DIR] [--work-tree=GIT_WORK_TREE]
  15    [--help] COMMAND [ARGS]
  16
  17DESCRIPTION
  18-----------
  19Git is a fast, scalable, distributed revision control system with an
  20unusually rich command set that provides both high-level operations
  21and full access to internals.
  22
  23See linkgit:gittutorial[7] to get started, then see
  24link:everyday.html[Everyday Git] for a useful minimum set of commands, and
  25"man git-commandname" for documentation of each command.  CVS users may
  26also want to read linkgit:gitcvs-migration[7].  See
  27the link:user-manual.html[Git User's Manual] for a more in-depth
  28introduction.
  29
  30The COMMAND is either a name of a Git command (see below) or an alias
  31as defined in the configuration file (see linkgit:git-config[1]).
  32
  33Formatted and hyperlinked version of the latest git
  34documentation can be viewed at
  35`http://www.kernel.org/pub/software/scm/git/docs/`.
  36
  37ifdef::stalenotes[]
  38[NOTE]
  39============
  40
  41You are reading the documentation for the latest (possibly
  42unreleased) version of git, that is available from 'master'
  43branch of the `git.git` repository.
  44Documentation for older releases are available here:
  45
  46* link:v1.7.0.1/git.html[documentation for release 1.7.0.1]
  47
  48* release notes for
  49  link:RelNotes-1.7.0.1.txt[1.7.0.1],
  50  link:RelNotes-1.7.0.txt[1.7.0].
  51
  52* link:v1.6.6.2/git.html[documentation for release 1.6.6.2]
  53
  54* release notes for
  55  link:RelNotes-1.6.6.2.txt[1.6.6.2],
  56  link:RelNotes-1.6.6.1.txt[1.6.6.1],
  57  link:RelNotes-1.6.6.txt[1.6.6].
  58
  59* link:v1.6.5.8/git.html[documentation for release 1.6.5.8]
  60
  61* release notes for
  62  link:RelNotes-1.6.5.8.txt[1.6.5.8],
  63  link:RelNotes-1.6.5.7.txt[1.6.5.7],
  64  link:RelNotes-1.6.5.6.txt[1.6.5.6],
  65  link:RelNotes-1.6.5.5.txt[1.6.5.5],
  66  link:RelNotes-1.6.5.4.txt[1.6.5.4],
  67  link:RelNotes-1.6.5.3.txt[1.6.5.3],
  68  link:RelNotes-1.6.5.2.txt[1.6.5.2],
  69  link:RelNotes-1.6.5.1.txt[1.6.5.1],
  70  link:RelNotes-1.6.5.txt[1.6.5].
  71
  72* link:v1.6.4.4/git.html[documentation for release 1.6.4.4]
  73
  74* release notes for
  75  link:RelNotes-1.6.4.4.txt[1.6.4.4],
  76  link:RelNotes-1.6.4.3.txt[1.6.4.3],
  77  link:RelNotes-1.6.4.2.txt[1.6.4.2],
  78  link:RelNotes-1.6.4.1.txt[1.6.4.1],
  79  link:RelNotes-1.6.4.txt[1.6.4].
  80
  81* link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
  82
  83* release notes for
  84  link:RelNotes-1.6.3.4.txt[1.6.3.4],
  85  link:RelNotes-1.6.3.3.txt[1.6.3.3],
  86  link:RelNotes-1.6.3.2.txt[1.6.3.2],
  87  link:RelNotes-1.6.3.1.txt[1.6.3.1],
  88  link:RelNotes-1.6.3.txt[1.6.3].
  89
  90* release notes for
  91  link:RelNotes-1.6.2.5.txt[1.6.2.5],
  92  link:RelNotes-1.6.2.4.txt[1.6.2.4],
  93  link:RelNotes-1.6.2.3.txt[1.6.2.3],
  94  link:RelNotes-1.6.2.2.txt[1.6.2.2],
  95  link:RelNotes-1.6.2.1.txt[1.6.2.1],
  96  link:RelNotes-1.6.2.txt[1.6.2].
  97
  98* link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
  99
 100* release notes for
 101  link:RelNotes-1.6.1.3.txt[1.6.1.3],
 102  link:RelNotes-1.6.1.2.txt[1.6.1.2],
 103  link:RelNotes-1.6.1.1.txt[1.6.1.1],
 104  link:RelNotes-1.6.1.txt[1.6.1].
 105
 106* link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 107
 108* release notes for
 109  link:RelNotes-1.6.0.6.txt[1.6.0.6],
 110  link:RelNotes-1.6.0.5.txt[1.6.0.5],
 111  link:RelNotes-1.6.0.4.txt[1.6.0.4],
 112  link:RelNotes-1.6.0.3.txt[1.6.0.3],
 113  link:RelNotes-1.6.0.2.txt[1.6.0.2],
 114  link:RelNotes-1.6.0.1.txt[1.6.0.1],
 115  link:RelNotes-1.6.0.txt[1.6.0].
 116
 117* link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 118
 119* release notes for
 120  link:RelNotes-1.5.6.6.txt[1.5.6.6],
 121  link:RelNotes-1.5.6.5.txt[1.5.6.5],
 122  link:RelNotes-1.5.6.4.txt[1.5.6.4],
 123  link:RelNotes-1.5.6.3.txt[1.5.6.3],
 124  link:RelNotes-1.5.6.2.txt[1.5.6.2],
 125  link:RelNotes-1.5.6.1.txt[1.5.6.1],
 126  link:RelNotes-1.5.6.txt[1.5.6].
 127
 128* link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 129
 130* release notes for
 131  link:RelNotes-1.5.5.6.txt[1.5.5.6],
 132  link:RelNotes-1.5.5.5.txt[1.5.5.5],
 133  link:RelNotes-1.5.5.4.txt[1.5.5.4],
 134  link:RelNotes-1.5.5.3.txt[1.5.5.3],
 135  link:RelNotes-1.5.5.2.txt[1.5.5.2],
 136  link:RelNotes-1.5.5.1.txt[1.5.5.1],
 137  link:RelNotes-1.5.5.txt[1.5.5].
 138
 139* link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 140
 141* release notes for
 142  link:RelNotes-1.5.4.7.txt[1.5.4.7],
 143  link:RelNotes-1.5.4.6.txt[1.5.4.6],
 144  link:RelNotes-1.5.4.5.txt[1.5.4.5],
 145  link:RelNotes-1.5.4.4.txt[1.5.4.4],
 146  link:RelNotes-1.5.4.3.txt[1.5.4.3],
 147  link:RelNotes-1.5.4.2.txt[1.5.4.2],
 148  link:RelNotes-1.5.4.1.txt[1.5.4.1],
 149  link:RelNotes-1.5.4.txt[1.5.4].
 150
 151* link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 152
 153* release notes for
 154  link:RelNotes-1.5.3.8.txt[1.5.3.8],
 155  link:RelNotes-1.5.3.7.txt[1.5.3.7],
 156  link:RelNotes-1.5.3.6.txt[1.5.3.6],
 157  link:RelNotes-1.5.3.5.txt[1.5.3.5],
 158  link:RelNotes-1.5.3.4.txt[1.5.3.4],
 159  link:RelNotes-1.5.3.3.txt[1.5.3.3],
 160  link:RelNotes-1.5.3.2.txt[1.5.3.2],
 161  link:RelNotes-1.5.3.1.txt[1.5.3.1],
 162  link:RelNotes-1.5.3.txt[1.5.3].
 163
 164* link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 165
 166* release notes for
 167  link:RelNotes-1.5.2.5.txt[1.5.2.5],
 168  link:RelNotes-1.5.2.4.txt[1.5.2.4],
 169  link:RelNotes-1.5.2.3.txt[1.5.2.3],
 170  link:RelNotes-1.5.2.2.txt[1.5.2.2],
 171  link:RelNotes-1.5.2.1.txt[1.5.2.1],
 172  link:RelNotes-1.5.2.txt[1.5.2].
 173
 174* link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 175
 176* release notes for
 177  link:RelNotes-1.5.1.6.txt[1.5.1.6],
 178  link:RelNotes-1.5.1.5.txt[1.5.1.5],
 179  link:RelNotes-1.5.1.4.txt[1.5.1.4],
 180  link:RelNotes-1.5.1.3.txt[1.5.1.3],
 181  link:RelNotes-1.5.1.2.txt[1.5.1.2],
 182  link:RelNotes-1.5.1.1.txt[1.5.1.1],
 183  link:RelNotes-1.5.1.txt[1.5.1].
 184
 185* link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 186
 187* release notes for
 188  link:RelNotes-1.5.0.7.txt[1.5.0.7],
 189  link:RelNotes-1.5.0.6.txt[1.5.0.6],
 190  link:RelNotes-1.5.0.5.txt[1.5.0.5],
 191  link:RelNotes-1.5.0.3.txt[1.5.0.3],
 192  link:RelNotes-1.5.0.2.txt[1.5.0.2],
 193  link:RelNotes-1.5.0.1.txt[1.5.0.1],
 194  link:RelNotes-1.5.0.txt[1.5.0].
 195
 196* documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 197  link:v1.3.3/git.html[1.3.3],
 198  link:v1.2.6/git.html[1.2.6],
 199  link:v1.0.13/git.html[1.0.13].
 200
 201============
 202
 203endif::stalenotes[]
 204
 205OPTIONS
 206-------
 207--version::
 208        Prints the git suite version that the 'git' program came from.
 209
 210--help::
 211        Prints the synopsis and a list of the most commonly used
 212        commands. If the option '--all' or '-a' is given then all
 213        available commands are printed. If a git command is named this
 214        option will bring up the manual page for that command.
 215+
 216Other options are available to control how the manual page is
 217displayed. See linkgit:git-help[1] for more information,
 218because `git --help ...` is converted internally into `git
 219help ...`.
 220
 221--exec-path::
 222        Path to wherever your core git programs are installed.
 223        This can also be controlled by setting the GIT_EXEC_PATH
 224        environment variable. If no path is given, 'git' will print
 225        the current setting and then exit.
 226
 227--html-path::
 228        Print the path to wherever your git HTML documentation is installed
 229        and exit.
 230
 231-p::
 232--paginate::
 233        Pipe all output into 'less' (or if set, $PAGER).
 234
 235--no-pager::
 236        Do not pipe git output into a pager.
 237
 238--git-dir=<path>::
 239        Set the path to the repository. This can also be controlled by
 240        setting the GIT_DIR environment variable. It can be an absolute
 241        path or relative path to current working directory.
 242
 243--work-tree=<path>::
 244        Set the path to the working tree.  The value will not be
 245        used in combination with repositories found automatically in
 246        a .git directory (i.e. $GIT_DIR is not set).
 247        This can also be controlled by setting the GIT_WORK_TREE
 248        environment variable and the core.worktree configuration
 249        variable. It can be an absolute path or relative path to
 250        the directory specified by --git-dir or GIT_DIR.
 251        Note: If --git-dir or GIT_DIR are specified but none of
 252        --work-tree, GIT_WORK_TREE and core.worktree is specified,
 253        the current working directory is regarded as the top directory
 254        of your working tree.
 255
 256--bare::
 257        Treat the repository as a bare repository.  If GIT_DIR
 258        environment is not set, it is set to the current working
 259        directory.
 260
 261--no-replace-objects::
 262        Do not use replacement refs to replace git objects. See
 263        linkgit:git-replace[1] for more information.
 264
 265
 266FURTHER DOCUMENTATION
 267---------------------
 268
 269See the references above to get started using git.  The following is
 270probably more detail than necessary for a first-time user.
 271
 272The link:user-manual.html#git-concepts[git concepts chapter of the
 273user-manual] and linkgit:gitcore-tutorial[7] both provide
 274introductions to the underlying git architecture.
 275
 276See linkgit:gitworkflows[7] for an overview of recommended workflows.
 277
 278See also the link:howto-index.html[howto] documents for some useful
 279examples.
 280
 281The internals are documented in the
 282link:technical/api-index.html[GIT API documentation].
 283
 284GIT COMMANDS
 285------------
 286
 287We divide git into high level ("porcelain") commands and low level
 288("plumbing") commands.
 289
 290High-level commands (porcelain)
 291-------------------------------
 292
 293We separate the porcelain commands into the main commands and some
 294ancillary user utilities.
 295
 296Main porcelain commands
 297~~~~~~~~~~~~~~~~~~~~~~~
 298
 299include::cmds-mainporcelain.txt[]
 300
 301Ancillary Commands
 302~~~~~~~~~~~~~~~~~~
 303Manipulators:
 304
 305include::cmds-ancillarymanipulators.txt[]
 306
 307Interrogators:
 308
 309include::cmds-ancillaryinterrogators.txt[]
 310
 311
 312Interacting with Others
 313~~~~~~~~~~~~~~~~~~~~~~~
 314
 315These commands are to interact with foreign SCM and with other
 316people via patch over e-mail.
 317
 318include::cmds-foreignscminterface.txt[]
 319
 320
 321Low-level commands (plumbing)
 322-----------------------------
 323
 324Although git includes its
 325own porcelain layer, its low-level commands are sufficient to support
 326development of alternative porcelains.  Developers of such porcelains
 327might start by reading about linkgit:git-update-index[1] and
 328linkgit:git-read-tree[1].
 329
 330The interface (input, output, set of options and the semantics)
 331to these low-level commands are meant to be a lot more stable
 332than Porcelain level commands, because these commands are
 333primarily for scripted use.  The interface to Porcelain commands
 334on the other hand are subject to change in order to improve the
 335end user experience.
 336
 337The following description divides
 338the low-level commands into commands that manipulate objects (in
 339the repository, index, and working tree), commands that interrogate and
 340compare objects, and commands that move objects and references between
 341repositories.
 342
 343
 344Manipulation commands
 345~~~~~~~~~~~~~~~~~~~~~
 346
 347include::cmds-plumbingmanipulators.txt[]
 348
 349
 350Interrogation commands
 351~~~~~~~~~~~~~~~~~~~~~~
 352
 353include::cmds-plumbinginterrogators.txt[]
 354
 355In general, the interrogate commands do not touch the files in
 356the working tree.
 357
 358
 359Synching repositories
 360~~~~~~~~~~~~~~~~~~~~~
 361
 362include::cmds-synchingrepositories.txt[]
 363
 364The following are helper commands used by the above; end users
 365typically do not use them directly.
 366
 367include::cmds-synchelpers.txt[]
 368
 369
 370Internal helper commands
 371~~~~~~~~~~~~~~~~~~~~~~~~
 372
 373These are internal helper commands used by other commands; end
 374users typically do not use them directly.
 375
 376include::cmds-purehelpers.txt[]
 377
 378
 379Configuration Mechanism
 380-----------------------
 381
 382Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 383is used to hold per-repository configuration options.  It is a
 384simple text file modeled after `.ini` format familiar to some
 385people.  Here is an example:
 386
 387------------
 388#
 389# A '#' or ';' character indicates a comment.
 390#
 391
 392; core variables
 393[core]
 394        ; Don't trust file modes
 395        filemode = false
 396
 397; user identity
 398[user]
 399        name = "Junio C Hamano"
 400        email = "junkio@twinsun.com"
 401
 402------------
 403
 404Various commands read from the configuration file and adjust
 405their operation accordingly.
 406
 407
 408Identifier Terminology
 409----------------------
 410<object>::
 411        Indicates the object name for any type of object.
 412
 413<blob>::
 414        Indicates a blob object name.
 415
 416<tree>::
 417        Indicates a tree object name.
 418
 419<commit>::
 420        Indicates a commit object name.
 421
 422<tree-ish>::
 423        Indicates a tree, commit or tag object name.  A
 424        command that takes a <tree-ish> argument ultimately wants to
 425        operate on a <tree> object but automatically dereferences
 426        <commit> and <tag> objects that point at a <tree>.
 427
 428<commit-ish>::
 429        Indicates a commit or tag object name.  A
 430        command that takes a <commit-ish> argument ultimately wants to
 431        operate on a <commit> object but automatically dereferences
 432        <tag> objects that point at a <commit>.
 433
 434<type>::
 435        Indicates that an object type is required.
 436        Currently one of: `blob`, `tree`, `commit`, or `tag`.
 437
 438<file>::
 439        Indicates a filename - almost always relative to the
 440        root of the tree structure `GIT_INDEX_FILE` describes.
 441
 442Symbolic Identifiers
 443--------------------
 444Any git command accepting any <object> can also use the following
 445symbolic notation:
 446
 447HEAD::
 448        indicates the head of the current branch (i.e. the
 449        contents of `$GIT_DIR/HEAD`).
 450
 451<tag>::
 452        a valid tag 'name'
 453        (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 454
 455<head>::
 456        a valid head 'name'
 457        (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 458
 459For a more complete list of ways to spell object names, see
 460"SPECIFYING REVISIONS" section in linkgit:git-rev-parse[1].
 461
 462
 463File/Directory Structure
 464------------------------
 465
 466Please see the linkgit:gitrepository-layout[5] document.
 467
 468Read linkgit:githooks[5] for more details about each hook.
 469
 470Higher level SCMs may provide and manage additional information in the
 471`$GIT_DIR`.
 472
 473
 474Terminology
 475-----------
 476Please see linkgit:gitglossary[7].
 477
 478
 479Environment Variables
 480---------------------
 481Various git commands use the following environment variables:
 482
 483The git Repository
 484~~~~~~~~~~~~~~~~~~
 485These environment variables apply to 'all' core git commands. Nb: it
 486is worth noting that they may be used/overridden by SCMS sitting above
 487git so take care if using Cogito etc.
 488
 489'GIT_INDEX_FILE'::
 490        This environment allows the specification of an alternate
 491        index file. If not specified, the default of `$GIT_DIR/index`
 492        is used.
 493
 494'GIT_OBJECT_DIRECTORY'::
 495        If the object storage directory is specified via this
 496        environment variable then the sha1 directories are created
 497        underneath - otherwise the default `$GIT_DIR/objects`
 498        directory is used.
 499
 500'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 501        Due to the immutable nature of git objects, old objects can be
 502        archived into shared, read-only directories. This variable
 503        specifies a ":" separated (on Windows ";" separated) list
 504        of git object directories which can be used to search for git
 505        objects. New objects will not be written to these directories.
 506
 507'GIT_DIR'::
 508        If the 'GIT_DIR' environment variable is set then it
 509        specifies a path to use instead of the default `.git`
 510        for the base of the repository.
 511
 512'GIT_WORK_TREE'::
 513        Set the path to the working tree.  The value will not be
 514        used in combination with repositories found automatically in
 515        a .git directory (i.e. $GIT_DIR is not set).
 516        This can also be controlled by the '--work-tree' command line
 517        option and the core.worktree configuration variable.
 518
 519'GIT_CEILING_DIRECTORIES'::
 520        This should be a colon-separated list of absolute paths.
 521        If set, it is a list of directories that git should not chdir
 522        up into while looking for a repository directory.
 523        It will not exclude the current working directory or
 524        a GIT_DIR set on the command line or in the environment.
 525        (Useful for excluding slow-loading network directories.)
 526
 527git Commits
 528~~~~~~~~~~~
 529'GIT_AUTHOR_NAME'::
 530'GIT_AUTHOR_EMAIL'::
 531'GIT_AUTHOR_DATE'::
 532'GIT_COMMITTER_NAME'::
 533'GIT_COMMITTER_EMAIL'::
 534'GIT_COMMITTER_DATE'::
 535'EMAIL'::
 536        see linkgit:git-commit-tree[1]
 537
 538git Diffs
 539~~~~~~~~~
 540'GIT_DIFF_OPTS'::
 541        Only valid setting is "--unified=??" or "-u??" to set the
 542        number of context lines shown when a unified diff is created.
 543        This takes precedence over any "-U" or "--unified" option
 544        value passed on the git diff command line.
 545
 546'GIT_EXTERNAL_DIFF'::
 547        When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 548        program named by it is called, instead of the diff invocation
 549        described above.  For a path that is added, removed, or modified,
 550        'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 551
 552        path old-file old-hex old-mode new-file new-hex new-mode
 553+
 554where:
 555
 556        <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 557                         contents of <old|new>,
 558        <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 559        <old|new>-mode:: are the octal representation of the file modes.
 560
 561+
 562The file parameters can point at the user's working file
 563(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 564when a new file is added), or a temporary file (e.g. `old-file` in the
 565index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 566temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 567+
 568For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 569parameter, <path>.
 570
 571other
 572~~~~~
 573'GIT_MERGE_VERBOSITY'::
 574        A number controlling the amount of output shown by
 575        the recursive merge strategy.  Overrides merge.verbosity.
 576        See linkgit:git-merge[1]
 577
 578'GIT_PAGER'::
 579        This environment variable overrides `$PAGER`. If it is set
 580        to an empty string or to the value "cat", git will not launch
 581        a pager.  See also the `core.pager` option in
 582        linkgit:git-config[1].
 583
 584'GIT_SSH'::
 585        If this environment variable is set then 'git fetch'
 586        and 'git push' will use this command instead
 587        of 'ssh' when they need to connect to a remote system.
 588        The '$GIT_SSH' command will be given exactly two arguments:
 589        the 'username@host' (or just 'host') from the URL and the
 590        shell command to execute on that remote system.
 591+
 592To pass options to the program that you want to list in GIT_SSH
 593you will need to wrap the program and options into a shell script,
 594then set GIT_SSH to refer to the shell script.
 595+
 596Usually it is easier to configure any desired options through your
 597personal `.ssh/config` file.  Please consult your ssh documentation
 598for further details.
 599
 600'GIT_FLUSH'::
 601        If this environment variable is set to "1", then commands such
 602        as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 603        and 'git whatchanged' will force a flush of the output stream
 604        after each commit-oriented record have been flushed.   If this
 605        variable is set to "0", the output of these commands will be done
 606        using completely buffered I/O.   If this environment variable is
 607        not set, git will choose buffered or record-oriented flushing
 608        based on whether stdout appears to be redirected to a file or not.
 609
 610'GIT_TRACE'::
 611        If this variable is set to "1", "2" or "true" (comparison
 612        is case insensitive), git will print `trace:` messages on
 613        stderr telling about alias expansion, built-in command
 614        execution and external command execution.
 615        If this variable is set to an integer value greater than 1
 616        and lower than 10 (strictly) then git will interpret this
 617        value as an open file descriptor and will try to write the
 618        trace messages into this file descriptor.
 619        Alternatively, if this variable is set to an absolute path
 620        (starting with a '/' character), git will interpret this
 621        as a file path and will try to write the trace messages
 622        into it.
 623
 624Discussion[[Discussion]]
 625------------------------
 626
 627More detail on the following is available from the
 628link:user-manual.html#git-concepts[git concepts chapter of the
 629user-manual] and linkgit:gitcore-tutorial[7].
 630
 631A git project normally consists of a working directory with a ".git"
 632subdirectory at the top level.  The .git directory contains, among other
 633things, a compressed object database representing the complete history
 634of the project, an "index" file which links that history to the current
 635contents of the working tree, and named pointers into that history such
 636as tags and branch heads.
 637
 638The object database contains objects of three main types: blobs, which
 639hold file data; trees, which point to blobs and other trees to build up
 640directory hierarchies; and commits, which each reference a single tree
 641and some number of parent commits.
 642
 643The commit, equivalent to what other systems call a "changeset" or
 644"version", represents a step in the project's history, and each parent
 645represents an immediately preceding step.  Commits with more than one
 646parent represent merges of independent lines of development.
 647
 648All objects are named by the SHA1 hash of their contents, normally
 649written as a string of 40 hex digits.  Such names are globally unique.
 650The entire history leading up to a commit can be vouched for by signing
 651just that commit.  A fourth object type, the tag, is provided for this
 652purpose.
 653
 654When first created, objects are stored in individual files, but for
 655efficiency may later be compressed together into "pack files".
 656
 657Named pointers called refs mark interesting points in history.  A ref
 658may contain the SHA1 name of an object or the name of another ref.  Refs
 659with names beginning `ref/head/` contain the SHA1 name of the most
 660recent commit (or "head") of a branch under development.  SHA1 names of
 661tags of interest are stored under `ref/tags/`.  A special ref named
 662`HEAD` contains the name of the currently checked-out branch.
 663
 664The index file is initialized with a list of all paths and, for each
 665path, a blob object and a set of attributes.  The blob object represents
 666the contents of the file as of the head of the current branch.  The
 667attributes (last modified time, size, etc.) are taken from the
 668corresponding file in the working tree.  Subsequent changes to the
 669working tree can be found by comparing these attributes.  The index may
 670be updated with new content, and new commits may be created from the
 671content stored in the index.
 672
 673The index is also capable of storing multiple entries (called "stages")
 674for a given pathname.  These stages are used to hold the various
 675unmerged version of a file when a merge is in progress.
 676
 677Authors
 678-------
 679* git's founding father is Linus Torvalds <torvalds@osdl.org>.
 680* The current git nurse is Junio C Hamano <gitster@pobox.com>.
 681* The git potty was written by Andreas Ericsson <ae@op5.se>.
 682* General upbringing is handled by the git-list <git@vger.kernel.org>.
 683
 684Documentation
 685--------------
 686The documentation for git suite was started by David Greaves
 687<david@dgreaves.com>, and later enhanced greatly by the
 688contributors on the git-list <git@vger.kernel.org>.
 689
 690SEE ALSO
 691--------
 692linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 693link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 694linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 695linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 696linkgit:gitworkflows[7]
 697
 698GIT
 699---
 700Part of the linkgit:git[1] suite