Documentation / git.txton commit Merge branch 'maint-1.6.6' into maint-1.7.0 (28bf4ba)
   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:v1.7.0.6/git.html[documentation for release 1.7.0.6]
  47
  48* release notes for
  49  link:RelNotes-1.7.0.6.txt[1.7.0.6],
  50  link:RelNotes-1.7.0.5.txt[1.7.0.5],
  51  link:RelNotes-1.7.0.4.txt[1.7.0.4],
  52  link:RelNotes-1.7.0.3.txt[1.7.0.3],
  53  link:RelNotes-1.7.0.2.txt[1.7.0.2],
  54  link:RelNotes-1.7.0.1.txt[1.7.0.1],
  55  link:RelNotes-1.7.0.txt[1.7.0].
  56
  57* link:v1.6.6.2/git.html[documentation for release 1.6.6.2]
  58
  59* release notes for
  60  link:RelNotes-1.6.6.2.txt[1.6.6.2],
  61  link:RelNotes-1.6.6.1.txt[1.6.6.1],
  62  link:RelNotes-1.6.6.txt[1.6.6].
  63
  64* link:v1.6.5.8/git.html[documentation for release 1.6.5.8]
  65
  66* release notes for
  67  link:RelNotes-1.6.5.8.txt[1.6.5.8],
  68  link:RelNotes-1.6.5.7.txt[1.6.5.7],
  69  link:RelNotes-1.6.5.6.txt[1.6.5.6],
  70  link:RelNotes-1.6.5.5.txt[1.6.5.5],
  71  link:RelNotes-1.6.5.4.txt[1.6.5.4],
  72  link:RelNotes-1.6.5.3.txt[1.6.5.3],
  73  link:RelNotes-1.6.5.2.txt[1.6.5.2],
  74  link:RelNotes-1.6.5.1.txt[1.6.5.1],
  75  link:RelNotes-1.6.5.txt[1.6.5].
  76
  77* link:v1.6.4.4/git.html[documentation for release 1.6.4.4]
  78
  79* release notes for
  80  link:RelNotes-1.6.4.4.txt[1.6.4.4],
  81  link:RelNotes-1.6.4.3.txt[1.6.4.3],
  82  link:RelNotes-1.6.4.2.txt[1.6.4.2],
  83  link:RelNotes-1.6.4.1.txt[1.6.4.1],
  84  link:RelNotes-1.6.4.txt[1.6.4].
  85
  86* link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
  87
  88* release notes for
  89  link:RelNotes-1.6.3.4.txt[1.6.3.4],
  90  link:RelNotes-1.6.3.3.txt[1.6.3.3],
  91  link:RelNotes-1.6.3.2.txt[1.6.3.2],
  92  link:RelNotes-1.6.3.1.txt[1.6.3.1],
  93  link:RelNotes-1.6.3.txt[1.6.3].
  94
  95* release notes for
  96  link:RelNotes-1.6.2.5.txt[1.6.2.5],
  97  link:RelNotes-1.6.2.4.txt[1.6.2.4],
  98  link:RelNotes-1.6.2.3.txt[1.6.2.3],
  99  link:RelNotes-1.6.2.2.txt[1.6.2.2],
 100  link:RelNotes-1.6.2.1.txt[1.6.2.1],
 101  link:RelNotes-1.6.2.txt[1.6.2].
 102
 103* link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
 104
 105* release notes for
 106  link:RelNotes-1.6.1.3.txt[1.6.1.3],
 107  link:RelNotes-1.6.1.2.txt[1.6.1.2],
 108  link:RelNotes-1.6.1.1.txt[1.6.1.1],
 109  link:RelNotes-1.6.1.txt[1.6.1].
 110
 111* link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 112
 113* release notes for
 114  link:RelNotes-1.6.0.6.txt[1.6.0.6],
 115  link:RelNotes-1.6.0.5.txt[1.6.0.5],
 116  link:RelNotes-1.6.0.4.txt[1.6.0.4],
 117  link:RelNotes-1.6.0.3.txt[1.6.0.3],
 118  link:RelNotes-1.6.0.2.txt[1.6.0.2],
 119  link:RelNotes-1.6.0.1.txt[1.6.0.1],
 120  link:RelNotes-1.6.0.txt[1.6.0].
 121
 122* link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 123
 124* release notes for
 125  link:RelNotes-1.5.6.6.txt[1.5.6.6],
 126  link:RelNotes-1.5.6.5.txt[1.5.6.5],
 127  link:RelNotes-1.5.6.4.txt[1.5.6.4],
 128  link:RelNotes-1.5.6.3.txt[1.5.6.3],
 129  link:RelNotes-1.5.6.2.txt[1.5.6.2],
 130  link:RelNotes-1.5.6.1.txt[1.5.6.1],
 131  link:RelNotes-1.5.6.txt[1.5.6].
 132
 133* link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 134
 135* release notes for
 136  link:RelNotes-1.5.5.6.txt[1.5.5.6],
 137  link:RelNotes-1.5.5.5.txt[1.5.5.5],
 138  link:RelNotes-1.5.5.4.txt[1.5.5.4],
 139  link:RelNotes-1.5.5.3.txt[1.5.5.3],
 140  link:RelNotes-1.5.5.2.txt[1.5.5.2],
 141  link:RelNotes-1.5.5.1.txt[1.5.5.1],
 142  link:RelNotes-1.5.5.txt[1.5.5].
 143
 144* link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 145
 146* release notes for
 147  link:RelNotes-1.5.4.7.txt[1.5.4.7],
 148  link:RelNotes-1.5.4.6.txt[1.5.4.6],
 149  link:RelNotes-1.5.4.5.txt[1.5.4.5],
 150  link:RelNotes-1.5.4.4.txt[1.5.4.4],
 151  link:RelNotes-1.5.4.3.txt[1.5.4.3],
 152  link:RelNotes-1.5.4.2.txt[1.5.4.2],
 153  link:RelNotes-1.5.4.1.txt[1.5.4.1],
 154  link:RelNotes-1.5.4.txt[1.5.4].
 155
 156* link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 157
 158* release notes for
 159  link:RelNotes-1.5.3.8.txt[1.5.3.8],
 160  link:RelNotes-1.5.3.7.txt[1.5.3.7],
 161  link:RelNotes-1.5.3.6.txt[1.5.3.6],
 162  link:RelNotes-1.5.3.5.txt[1.5.3.5],
 163  link:RelNotes-1.5.3.4.txt[1.5.3.4],
 164  link:RelNotes-1.5.3.3.txt[1.5.3.3],
 165  link:RelNotes-1.5.3.2.txt[1.5.3.2],
 166  link:RelNotes-1.5.3.1.txt[1.5.3.1],
 167  link:RelNotes-1.5.3.txt[1.5.3].
 168
 169* link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 170
 171* release notes for
 172  link:RelNotes-1.5.2.5.txt[1.5.2.5],
 173  link:RelNotes-1.5.2.4.txt[1.5.2.4],
 174  link:RelNotes-1.5.2.3.txt[1.5.2.3],
 175  link:RelNotes-1.5.2.2.txt[1.5.2.2],
 176  link:RelNotes-1.5.2.1.txt[1.5.2.1],
 177  link:RelNotes-1.5.2.txt[1.5.2].
 178
 179* link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 180
 181* release notes for
 182  link:RelNotes-1.5.1.6.txt[1.5.1.6],
 183  link:RelNotes-1.5.1.5.txt[1.5.1.5],
 184  link:RelNotes-1.5.1.4.txt[1.5.1.4],
 185  link:RelNotes-1.5.1.3.txt[1.5.1.3],
 186  link:RelNotes-1.5.1.2.txt[1.5.1.2],
 187  link:RelNotes-1.5.1.1.txt[1.5.1.1],
 188  link:RelNotes-1.5.1.txt[1.5.1].
 189
 190* link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 191
 192* release notes for
 193  link:RelNotes-1.5.0.7.txt[1.5.0.7],
 194  link:RelNotes-1.5.0.6.txt[1.5.0.6],
 195  link:RelNotes-1.5.0.5.txt[1.5.0.5],
 196  link:RelNotes-1.5.0.3.txt[1.5.0.3],
 197  link:RelNotes-1.5.0.2.txt[1.5.0.2],
 198  link:RelNotes-1.5.0.1.txt[1.5.0.1],
 199  link:RelNotes-1.5.0.txt[1.5.0].
 200
 201* documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 202  link:v1.3.3/git.html[1.3.3],
 203  link:v1.2.6/git.html[1.2.6],
 204  link:v1.0.13/git.html[1.0.13].
 205
 206============
 207
 208endif::stalenotes[]
 209
 210OPTIONS
 211-------
 212--version::
 213        Prints the git suite version that the 'git' program came from.
 214
 215--help::
 216        Prints the synopsis and a list of the most commonly used
 217        commands. If the option '--all' or '-a' is given then all
 218        available commands are printed. If a git command is named this
 219        option will bring up the manual page for that command.
 220+
 221Other options are available to control how the manual page is
 222displayed. See linkgit:git-help[1] for more information,
 223because `git --help ...` is converted internally into `git
 224help ...`.
 225
 226--exec-path::
 227        Path to wherever your core git programs are installed.
 228        This can also be controlled by setting the GIT_EXEC_PATH
 229        environment variable. If no path is given, 'git' will print
 230        the current setting and then exit.
 231
 232--html-path::
 233        Print the path to wherever your git HTML documentation is installed
 234        and exit.
 235
 236-p::
 237--paginate::
 238        Pipe all output into 'less' (or if set, $PAGER) if standard
 239        output is a terminal.  This overrides the `pager.<cmd>`
 240        configuration options (see the "Configuration Mechanism" section
 241        below).
 242
 243--no-pager::
 244        Do not pipe git output into a pager.
 245
 246--git-dir=<path>::
 247        Set the path to the repository. This can also be controlled by
 248        setting the GIT_DIR environment variable. It can be an absolute
 249        path or relative path to current working directory.
 250
 251--work-tree=<path>::
 252        Set the path to the working tree.  The value will not be
 253        used in combination with repositories found automatically in
 254        a .git directory (i.e. $GIT_DIR is not set).
 255        This can also be controlled by setting the GIT_WORK_TREE
 256        environment variable and the core.worktree configuration
 257        variable. It can be an absolute path or relative path to
 258        the directory specified by --git-dir or GIT_DIR.
 259        Note: If --git-dir or GIT_DIR are specified but none of
 260        --work-tree, GIT_WORK_TREE and core.worktree is specified,
 261        the current working directory is regarded as the top directory
 262        of your working tree.
 263
 264--bare::
 265        Treat the repository as a bare repository.  If GIT_DIR
 266        environment is not set, it is set to the current working
 267        directory.
 268
 269--no-replace-objects::
 270        Do not use replacement refs to replace git objects. See
 271        linkgit:git-replace[1] for more information.
 272
 273
 274FURTHER DOCUMENTATION
 275---------------------
 276
 277See the references above to get started using git.  The following is
 278probably more detail than necessary for a first-time user.
 279
 280The link:user-manual.html#git-concepts[git concepts chapter of the
 281user-manual] and linkgit:gitcore-tutorial[7] both provide
 282introductions to the underlying git architecture.
 283
 284See linkgit:gitworkflows[7] for an overview of recommended workflows.
 285
 286See also the link:howto-index.html[howto] documents for some useful
 287examples.
 288
 289The internals are documented in the
 290link:technical/api-index.html[GIT API documentation].
 291
 292GIT COMMANDS
 293------------
 294
 295We divide git into high level ("porcelain") commands and low level
 296("plumbing") commands.
 297
 298High-level commands (porcelain)
 299-------------------------------
 300
 301We separate the porcelain commands into the main commands and some
 302ancillary user utilities.
 303
 304Main porcelain commands
 305~~~~~~~~~~~~~~~~~~~~~~~
 306
 307include::cmds-mainporcelain.txt[]
 308
 309Ancillary Commands
 310~~~~~~~~~~~~~~~~~~
 311Manipulators:
 312
 313include::cmds-ancillarymanipulators.txt[]
 314
 315Interrogators:
 316
 317include::cmds-ancillaryinterrogators.txt[]
 318
 319
 320Interacting with Others
 321~~~~~~~~~~~~~~~~~~~~~~~
 322
 323These commands are to interact with foreign SCM and with other
 324people via patch over e-mail.
 325
 326include::cmds-foreignscminterface.txt[]
 327
 328
 329Low-level commands (plumbing)
 330-----------------------------
 331
 332Although git includes its
 333own porcelain layer, its low-level commands are sufficient to support
 334development of alternative porcelains.  Developers of such porcelains
 335might start by reading about linkgit:git-update-index[1] and
 336linkgit:git-read-tree[1].
 337
 338The interface (input, output, set of options and the semantics)
 339to these low-level commands are meant to be a lot more stable
 340than Porcelain level commands, because these commands are
 341primarily for scripted use.  The interface to Porcelain commands
 342on the other hand are subject to change in order to improve the
 343end user experience.
 344
 345The following description divides
 346the low-level commands into commands that manipulate objects (in
 347the repository, index, and working tree), commands that interrogate and
 348compare objects, and commands that move objects and references between
 349repositories.
 350
 351
 352Manipulation commands
 353~~~~~~~~~~~~~~~~~~~~~
 354
 355include::cmds-plumbingmanipulators.txt[]
 356
 357
 358Interrogation commands
 359~~~~~~~~~~~~~~~~~~~~~~
 360
 361include::cmds-plumbinginterrogators.txt[]
 362
 363In general, the interrogate commands do not touch the files in
 364the working tree.
 365
 366
 367Synching repositories
 368~~~~~~~~~~~~~~~~~~~~~
 369
 370include::cmds-synchingrepositories.txt[]
 371
 372The following are helper commands used by the above; end users
 373typically do not use them directly.
 374
 375include::cmds-synchelpers.txt[]
 376
 377
 378Internal helper commands
 379~~~~~~~~~~~~~~~~~~~~~~~~
 380
 381These are internal helper commands used by other commands; end
 382users typically do not use them directly.
 383
 384include::cmds-purehelpers.txt[]
 385
 386
 387Configuration Mechanism
 388-----------------------
 389
 390Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 391is used to hold per-repository configuration options.  It is a
 392simple text file modeled after `.ini` format familiar to some
 393people.  Here is an example:
 394
 395------------
 396#
 397# A '#' or ';' character indicates a comment.
 398#
 399
 400; core variables
 401[core]
 402        ; Don't trust file modes
 403        filemode = false
 404
 405; user identity
 406[user]
 407        name = "Junio C Hamano"
 408        email = "junkio@twinsun.com"
 409
 410------------
 411
 412Various commands read from the configuration file and adjust
 413their operation accordingly.  See linkgit:git-config[1] for a
 414list.
 415
 416
 417Identifier Terminology
 418----------------------
 419<object>::
 420        Indicates the object name for any type of object.
 421
 422<blob>::
 423        Indicates a blob object name.
 424
 425<tree>::
 426        Indicates a tree object name.
 427
 428<commit>::
 429        Indicates a commit object name.
 430
 431<tree-ish>::
 432        Indicates a tree, commit or tag object name.  A
 433        command that takes a <tree-ish> argument ultimately wants to
 434        operate on a <tree> object but automatically dereferences
 435        <commit> and <tag> objects that point at a <tree>.
 436
 437<commit-ish>::
 438        Indicates a commit or tag object name.  A
 439        command that takes a <commit-ish> argument ultimately wants to
 440        operate on a <commit> object but automatically dereferences
 441        <tag> objects that point at a <commit>.
 442
 443<type>::
 444        Indicates that an object type is required.
 445        Currently one of: `blob`, `tree`, `commit`, or `tag`.
 446
 447<file>::
 448        Indicates a filename - almost always relative to the
 449        root of the tree structure `GIT_INDEX_FILE` describes.
 450
 451Symbolic Identifiers
 452--------------------
 453Any git command accepting any <object> can also use the following
 454symbolic notation:
 455
 456HEAD::
 457        indicates the head of the current branch (i.e. the
 458        contents of `$GIT_DIR/HEAD`).
 459
 460<tag>::
 461        a valid tag 'name'
 462        (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 463
 464<head>::
 465        a valid head 'name'
 466        (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 467
 468For a more complete list of ways to spell object names, see
 469"SPECIFYING REVISIONS" section in linkgit:git-rev-parse[1].
 470
 471
 472File/Directory Structure
 473------------------------
 474
 475Please see the linkgit:gitrepository-layout[5] document.
 476
 477Read linkgit:githooks[5] for more details about each hook.
 478
 479Higher level SCMs may provide and manage additional information in the
 480`$GIT_DIR`.
 481
 482
 483Terminology
 484-----------
 485Please see linkgit:gitglossary[7].
 486
 487
 488Environment Variables
 489---------------------
 490Various git commands use the following environment variables:
 491
 492The git Repository
 493~~~~~~~~~~~~~~~~~~
 494These environment variables apply to 'all' core git commands. Nb: it
 495is worth noting that they may be used/overridden by SCMS sitting above
 496git so take care if using Cogito etc.
 497
 498'GIT_INDEX_FILE'::
 499        This environment allows the specification of an alternate
 500        index file. If not specified, the default of `$GIT_DIR/index`
 501        is used.
 502
 503'GIT_OBJECT_DIRECTORY'::
 504        If the object storage directory is specified via this
 505        environment variable then the sha1 directories are created
 506        underneath - otherwise the default `$GIT_DIR/objects`
 507        directory is used.
 508
 509'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 510        Due to the immutable nature of git objects, old objects can be
 511        archived into shared, read-only directories. This variable
 512        specifies a ":" separated (on Windows ";" separated) list
 513        of git object directories which can be used to search for git
 514        objects. New objects will not be written to these directories.
 515
 516'GIT_DIR'::
 517        If the 'GIT_DIR' environment variable is set then it
 518        specifies a path to use instead of the default `.git`
 519        for the base of the repository.
 520
 521'GIT_WORK_TREE'::
 522        Set the path to the working tree.  The value will not be
 523        used in combination with repositories found automatically in
 524        a .git directory (i.e. $GIT_DIR is not set).
 525        This can also be controlled by the '--work-tree' command line
 526        option and the core.worktree configuration variable.
 527
 528'GIT_CEILING_DIRECTORIES'::
 529        This should be a colon-separated list of absolute paths.
 530        If set, it is a list of directories that git should not chdir
 531        up into while looking for a repository directory.
 532        It will not exclude the current working directory or
 533        a GIT_DIR set on the command line or in the environment.
 534        (Useful for excluding slow-loading network directories.)
 535
 536git Commits
 537~~~~~~~~~~~
 538'GIT_AUTHOR_NAME'::
 539'GIT_AUTHOR_EMAIL'::
 540'GIT_AUTHOR_DATE'::
 541'GIT_COMMITTER_NAME'::
 542'GIT_COMMITTER_EMAIL'::
 543'GIT_COMMITTER_DATE'::
 544'EMAIL'::
 545        see linkgit:git-commit-tree[1]
 546
 547git Diffs
 548~~~~~~~~~
 549'GIT_DIFF_OPTS'::
 550        Only valid setting is "--unified=??" or "-u??" to set the
 551        number of context lines shown when a unified diff is created.
 552        This takes precedence over any "-U" or "--unified" option
 553        value passed on the git diff command line.
 554
 555'GIT_EXTERNAL_DIFF'::
 556        When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 557        program named by it is called, instead of the diff invocation
 558        described above.  For a path that is added, removed, or modified,
 559        'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 560
 561        path old-file old-hex old-mode new-file new-hex new-mode
 562+
 563where:
 564
 565        <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 566                         contents of <old|new>,
 567        <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 568        <old|new>-mode:: are the octal representation of the file modes.
 569
 570+
 571The file parameters can point at the user's working file
 572(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 573when a new file is added), or a temporary file (e.g. `old-file` in the
 574index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 575temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 576+
 577For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 578parameter, <path>.
 579
 580other
 581~~~~~
 582'GIT_MERGE_VERBOSITY'::
 583        A number controlling the amount of output shown by
 584        the recursive merge strategy.  Overrides merge.verbosity.
 585        See linkgit:git-merge[1]
 586
 587'GIT_PAGER'::
 588        This environment variable overrides `$PAGER`. If it is set
 589        to an empty string or to the value "cat", git will not launch
 590        a pager.  See also the `core.pager` option in
 591        linkgit:git-config[1].
 592
 593'GIT_SSH'::
 594        If this environment variable is set then 'git fetch'
 595        and 'git push' will use this command instead
 596        of 'ssh' when they need to connect to a remote system.
 597        The '$GIT_SSH' command will be given exactly two arguments:
 598        the 'username@host' (or just 'host') from the URL and the
 599        shell command to execute on that remote system.
 600+
 601To pass options to the program that you want to list in GIT_SSH
 602you will need to wrap the program and options into a shell script,
 603then set GIT_SSH to refer to the shell script.
 604+
 605Usually it is easier to configure any desired options through your
 606personal `.ssh/config` file.  Please consult your ssh documentation
 607for further details.
 608
 609'GIT_FLUSH'::
 610        If this environment variable is set to "1", then commands such
 611        as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 612        and 'git whatchanged' will force a flush of the output stream
 613        after each commit-oriented record have been flushed.   If this
 614        variable is set to "0", the output of these commands will be done
 615        using completely buffered I/O.   If this environment variable is
 616        not set, git will choose buffered or record-oriented flushing
 617        based on whether stdout appears to be redirected to a file or not.
 618
 619'GIT_TRACE'::
 620        If this variable is set to "1", "2" or "true" (comparison
 621        is case insensitive), git will print `trace:` messages on
 622        stderr telling about alias expansion, built-in command
 623        execution and external command execution.
 624        If this variable is set to an integer value greater than 1
 625        and lower than 10 (strictly) then git will interpret this
 626        value as an open file descriptor and will try to write the
 627        trace messages into this file descriptor.
 628        Alternatively, if this variable is set to an absolute path
 629        (starting with a '/' character), git will interpret this
 630        as a file path and will try to write the trace messages
 631        into it.
 632
 633Discussion[[Discussion]]
 634------------------------
 635
 636More detail on the following is available from the
 637link:user-manual.html#git-concepts[git concepts chapter of the
 638user-manual] and linkgit:gitcore-tutorial[7].
 639
 640A git project normally consists of a working directory with a ".git"
 641subdirectory at the top level.  The .git directory contains, among other
 642things, a compressed object database representing the complete history
 643of the project, an "index" file which links that history to the current
 644contents of the working tree, and named pointers into that history such
 645as tags and branch heads.
 646
 647The object database contains objects of three main types: blobs, which
 648hold file data; trees, which point to blobs and other trees to build up
 649directory hierarchies; and commits, which each reference a single tree
 650and some number of parent commits.
 651
 652The commit, equivalent to what other systems call a "changeset" or
 653"version", represents a step in the project's history, and each parent
 654represents an immediately preceding step.  Commits with more than one
 655parent represent merges of independent lines of development.
 656
 657All objects are named by the SHA1 hash of their contents, normally
 658written as a string of 40 hex digits.  Such names are globally unique.
 659The entire history leading up to a commit can be vouched for by signing
 660just that commit.  A fourth object type, the tag, is provided for this
 661purpose.
 662
 663When first created, objects are stored in individual files, but for
 664efficiency may later be compressed together into "pack files".
 665
 666Named pointers called refs mark interesting points in history.  A ref
 667may contain the SHA1 name of an object or the name of another ref.  Refs
 668with names beginning `ref/head/` contain the SHA1 name of the most
 669recent commit (or "head") of a branch under development.  SHA1 names of
 670tags of interest are stored under `ref/tags/`.  A special ref named
 671`HEAD` contains the name of the currently checked-out branch.
 672
 673The index file is initialized with a list of all paths and, for each
 674path, a blob object and a set of attributes.  The blob object represents
 675the contents of the file as of the head of the current branch.  The
 676attributes (last modified time, size, etc.) are taken from the
 677corresponding file in the working tree.  Subsequent changes to the
 678working tree can be found by comparing these attributes.  The index may
 679be updated with new content, and new commits may be created from the
 680content stored in the index.
 681
 682The index is also capable of storing multiple entries (called "stages")
 683for a given pathname.  These stages are used to hold the various
 684unmerged version of a file when a merge is in progress.
 685
 686Authors
 687-------
 688* git's founding father is Linus Torvalds <torvalds@osdl.org>.
 689* The current git nurse is Junio C Hamano <gitster@pobox.com>.
 690* The git potty was written by Andreas Ericsson <ae@op5.se>.
 691* General upbringing is handled by the git-list <git@vger.kernel.org>.
 692
 693Documentation
 694--------------
 695The documentation for git suite was started by David Greaves
 696<david@dgreaves.com>, and later enhanced greatly by the
 697contributors on the git-list <git@vger.kernel.org>.
 698
 699SEE ALSO
 700--------
 701linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 702link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 703linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 704linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 705linkgit:gitworkflows[7]
 706
 707GIT
 708---
 709Part of the linkgit:git[1] suite