Documentation / git.txton commit Documentation/config.txt: default gc.aggressiveWindow is 250, not 10 (f78683f)
   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:v1.7.0.5/git.html[documentation for release 1.7.0.5]
  47
  48* release notes for
  49  link:RelNotes-1.7.0.5.txt[1.7.0.5],
  50  link:RelNotes-1.7.0.4.txt[1.7.0.4],
  51  link:RelNotes-1.7.0.3.txt[1.7.0.3],
  52  link:RelNotes-1.7.0.2.txt[1.7.0.2],
  53  link:RelNotes-1.7.0.1.txt[1.7.0.1],
  54  link:RelNotes-1.7.0.txt[1.7.0].
  55
  56* link:v1.6.6.2/git.html[documentation for release 1.6.6.2]
  57
  58* release notes for
  59  link:RelNotes-1.6.6.2.txt[1.6.6.2],
  60  link:RelNotes-1.6.6.1.txt[1.6.6.1],
  61  link:RelNotes-1.6.6.txt[1.6.6].
  62
  63* link:v1.6.5.8/git.html[documentation for release 1.6.5.8]
  64
  65* release notes for
  66  link:RelNotes-1.6.5.8.txt[1.6.5.8],
  67  link:RelNotes-1.6.5.7.txt[1.6.5.7],
  68  link:RelNotes-1.6.5.6.txt[1.6.5.6],
  69  link:RelNotes-1.6.5.5.txt[1.6.5.5],
  70  link:RelNotes-1.6.5.4.txt[1.6.5.4],
  71  link:RelNotes-1.6.5.3.txt[1.6.5.3],
  72  link:RelNotes-1.6.5.2.txt[1.6.5.2],
  73  link:RelNotes-1.6.5.1.txt[1.6.5.1],
  74  link:RelNotes-1.6.5.txt[1.6.5].
  75
  76* link:v1.6.4.4/git.html[documentation for release 1.6.4.4]
  77
  78* release notes for
  79  link:RelNotes-1.6.4.4.txt[1.6.4.4],
  80  link:RelNotes-1.6.4.3.txt[1.6.4.3],
  81  link:RelNotes-1.6.4.2.txt[1.6.4.2],
  82  link:RelNotes-1.6.4.1.txt[1.6.4.1],
  83  link:RelNotes-1.6.4.txt[1.6.4].
  84
  85* link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
  86
  87* release notes for
  88  link:RelNotes-1.6.3.4.txt[1.6.3.4],
  89  link:RelNotes-1.6.3.3.txt[1.6.3.3],
  90  link:RelNotes-1.6.3.2.txt[1.6.3.2],
  91  link:RelNotes-1.6.3.1.txt[1.6.3.1],
  92  link:RelNotes-1.6.3.txt[1.6.3].
  93
  94* release notes for
  95  link:RelNotes-1.6.2.5.txt[1.6.2.5],
  96  link:RelNotes-1.6.2.4.txt[1.6.2.4],
  97  link:RelNotes-1.6.2.3.txt[1.6.2.3],
  98  link:RelNotes-1.6.2.2.txt[1.6.2.2],
  99  link:RelNotes-1.6.2.1.txt[1.6.2.1],
 100  link:RelNotes-1.6.2.txt[1.6.2].
 101
 102* link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
 103
 104* release notes for
 105  link:RelNotes-1.6.1.3.txt[1.6.1.3],
 106  link:RelNotes-1.6.1.2.txt[1.6.1.2],
 107  link:RelNotes-1.6.1.1.txt[1.6.1.1],
 108  link:RelNotes-1.6.1.txt[1.6.1].
 109
 110* link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 111
 112* release notes for
 113  link:RelNotes-1.6.0.6.txt[1.6.0.6],
 114  link:RelNotes-1.6.0.5.txt[1.6.0.5],
 115  link:RelNotes-1.6.0.4.txt[1.6.0.4],
 116  link:RelNotes-1.6.0.3.txt[1.6.0.3],
 117  link:RelNotes-1.6.0.2.txt[1.6.0.2],
 118  link:RelNotes-1.6.0.1.txt[1.6.0.1],
 119  link:RelNotes-1.6.0.txt[1.6.0].
 120
 121* link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 122
 123* release notes for
 124  link:RelNotes-1.5.6.6.txt[1.5.6.6],
 125  link:RelNotes-1.5.6.5.txt[1.5.6.5],
 126  link:RelNotes-1.5.6.4.txt[1.5.6.4],
 127  link:RelNotes-1.5.6.3.txt[1.5.6.3],
 128  link:RelNotes-1.5.6.2.txt[1.5.6.2],
 129  link:RelNotes-1.5.6.1.txt[1.5.6.1],
 130  link:RelNotes-1.5.6.txt[1.5.6].
 131
 132* link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 133
 134* release notes for
 135  link:RelNotes-1.5.5.6.txt[1.5.5.6],
 136  link:RelNotes-1.5.5.5.txt[1.5.5.5],
 137  link:RelNotes-1.5.5.4.txt[1.5.5.4],
 138  link:RelNotes-1.5.5.3.txt[1.5.5.3],
 139  link:RelNotes-1.5.5.2.txt[1.5.5.2],
 140  link:RelNotes-1.5.5.1.txt[1.5.5.1],
 141  link:RelNotes-1.5.5.txt[1.5.5].
 142
 143* link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 144
 145* release notes for
 146  link:RelNotes-1.5.4.7.txt[1.5.4.7],
 147  link:RelNotes-1.5.4.6.txt[1.5.4.6],
 148  link:RelNotes-1.5.4.5.txt[1.5.4.5],
 149  link:RelNotes-1.5.4.4.txt[1.5.4.4],
 150  link:RelNotes-1.5.4.3.txt[1.5.4.3],
 151  link:RelNotes-1.5.4.2.txt[1.5.4.2],
 152  link:RelNotes-1.5.4.1.txt[1.5.4.1],
 153  link:RelNotes-1.5.4.txt[1.5.4].
 154
 155* link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 156
 157* release notes for
 158  link:RelNotes-1.5.3.8.txt[1.5.3.8],
 159  link:RelNotes-1.5.3.7.txt[1.5.3.7],
 160  link:RelNotes-1.5.3.6.txt[1.5.3.6],
 161  link:RelNotes-1.5.3.5.txt[1.5.3.5],
 162  link:RelNotes-1.5.3.4.txt[1.5.3.4],
 163  link:RelNotes-1.5.3.3.txt[1.5.3.3],
 164  link:RelNotes-1.5.3.2.txt[1.5.3.2],
 165  link:RelNotes-1.5.3.1.txt[1.5.3.1],
 166  link:RelNotes-1.5.3.txt[1.5.3].
 167
 168* link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 169
 170* release notes for
 171  link:RelNotes-1.5.2.5.txt[1.5.2.5],
 172  link:RelNotes-1.5.2.4.txt[1.5.2.4],
 173  link:RelNotes-1.5.2.3.txt[1.5.2.3],
 174  link:RelNotes-1.5.2.2.txt[1.5.2.2],
 175  link:RelNotes-1.5.2.1.txt[1.5.2.1],
 176  link:RelNotes-1.5.2.txt[1.5.2].
 177
 178* link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 179
 180* release notes for
 181  link:RelNotes-1.5.1.6.txt[1.5.1.6],
 182  link:RelNotes-1.5.1.5.txt[1.5.1.5],
 183  link:RelNotes-1.5.1.4.txt[1.5.1.4],
 184  link:RelNotes-1.5.1.3.txt[1.5.1.3],
 185  link:RelNotes-1.5.1.2.txt[1.5.1.2],
 186  link:RelNotes-1.5.1.1.txt[1.5.1.1],
 187  link:RelNotes-1.5.1.txt[1.5.1].
 188
 189* link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 190
 191* release notes for
 192  link:RelNotes-1.5.0.7.txt[1.5.0.7],
 193  link:RelNotes-1.5.0.6.txt[1.5.0.6],
 194  link:RelNotes-1.5.0.5.txt[1.5.0.5],
 195  link:RelNotes-1.5.0.3.txt[1.5.0.3],
 196  link:RelNotes-1.5.0.2.txt[1.5.0.2],
 197  link:RelNotes-1.5.0.1.txt[1.5.0.1],
 198  link:RelNotes-1.5.0.txt[1.5.0].
 199
 200* documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 201  link:v1.3.3/git.html[1.3.3],
 202  link:v1.2.6/git.html[1.2.6],
 203  link:v1.0.13/git.html[1.0.13].
 204
 205============
 206
 207endif::stalenotes[]
 208
 209OPTIONS
 210-------
 211--version::
 212        Prints the git suite version that the 'git' program came from.
 213
 214--help::
 215        Prints the synopsis and a list of the most commonly used
 216        commands. If the option '--all' or '-a' is given then all
 217        available commands are printed. If a git command is named this
 218        option will bring up the manual page for that command.
 219+
 220Other options are available to control how the manual page is
 221displayed. See linkgit:git-help[1] for more information,
 222because `git --help ...` is converted internally into `git
 223help ...`.
 224
 225--exec-path::
 226        Path to wherever your core git programs are installed.
 227        This can also be controlled by setting the GIT_EXEC_PATH
 228        environment variable. If no path is given, 'git' will print
 229        the current setting and then exit.
 230
 231--html-path::
 232        Print the path to wherever your git HTML documentation is installed
 233        and exit.
 234
 235-p::
 236--paginate::
 237        Pipe all output into 'less' (or if set, $PAGER) if standard
 238        output is a terminal.  This overrides the `pager.<cmd>`
 239        configuration options (see the "Configuration Mechanism" section
 240        below).
 241
 242--no-pager::
 243        Do not pipe git output into a pager.
 244
 245--git-dir=<path>::
 246        Set the path to the repository. This can also be controlled by
 247        setting the GIT_DIR environment variable. It can be an absolute
 248        path or relative path to current working directory.
 249
 250--work-tree=<path>::
 251        Set the path to the working tree.  The value will not be
 252        used in combination with repositories found automatically in
 253        a .git directory (i.e. $GIT_DIR is not set).
 254        This can also be controlled by setting the GIT_WORK_TREE
 255        environment variable and the core.worktree configuration
 256        variable. It can be an absolute path or relative path to
 257        the directory specified by --git-dir or GIT_DIR.
 258        Note: If --git-dir or GIT_DIR are specified but none of
 259        --work-tree, GIT_WORK_TREE and core.worktree is specified,
 260        the current working directory is regarded as the top directory
 261        of your working tree.
 262
 263--bare::
 264        Treat the repository as a bare repository.  If GIT_DIR
 265        environment is not set, it is set to the current working
 266        directory.
 267
 268--no-replace-objects::
 269        Do not use replacement refs to replace git objects. See
 270        linkgit:git-replace[1] for more information.
 271
 272
 273FURTHER DOCUMENTATION
 274---------------------
 275
 276See the references above to get started using git.  The following is
 277probably more detail than necessary for a first-time user.
 278
 279The link:user-manual.html#git-concepts[git concepts chapter of the
 280user-manual] and linkgit:gitcore-tutorial[7] both provide
 281introductions to the underlying git architecture.
 282
 283See linkgit:gitworkflows[7] for an overview of recommended workflows.
 284
 285See also the link:howto-index.html[howto] documents for some useful
 286examples.
 287
 288The internals are documented in the
 289link:technical/api-index.html[GIT API documentation].
 290
 291GIT COMMANDS
 292------------
 293
 294We divide git into high level ("porcelain") commands and low level
 295("plumbing") commands.
 296
 297High-level commands (porcelain)
 298-------------------------------
 299
 300We separate the porcelain commands into the main commands and some
 301ancillary user utilities.
 302
 303Main porcelain commands
 304~~~~~~~~~~~~~~~~~~~~~~~
 305
 306include::cmds-mainporcelain.txt[]
 307
 308Ancillary Commands
 309~~~~~~~~~~~~~~~~~~
 310Manipulators:
 311
 312include::cmds-ancillarymanipulators.txt[]
 313
 314Interrogators:
 315
 316include::cmds-ancillaryinterrogators.txt[]
 317
 318
 319Interacting with Others
 320~~~~~~~~~~~~~~~~~~~~~~~
 321
 322These commands are to interact with foreign SCM and with other
 323people via patch over e-mail.
 324
 325include::cmds-foreignscminterface.txt[]
 326
 327
 328Low-level commands (plumbing)
 329-----------------------------
 330
 331Although git includes its
 332own porcelain layer, its low-level commands are sufficient to support
 333development of alternative porcelains.  Developers of such porcelains
 334might start by reading about linkgit:git-update-index[1] and
 335linkgit:git-read-tree[1].
 336
 337The interface (input, output, set of options and the semantics)
 338to these low-level commands are meant to be a lot more stable
 339than Porcelain level commands, because these commands are
 340primarily for scripted use.  The interface to Porcelain commands
 341on the other hand are subject to change in order to improve the
 342end user experience.
 343
 344The following description divides
 345the low-level commands into commands that manipulate objects (in
 346the repository, index, and working tree), commands that interrogate and
 347compare objects, and commands that move objects and references between
 348repositories.
 349
 350
 351Manipulation commands
 352~~~~~~~~~~~~~~~~~~~~~
 353
 354include::cmds-plumbingmanipulators.txt[]
 355
 356
 357Interrogation commands
 358~~~~~~~~~~~~~~~~~~~~~~
 359
 360include::cmds-plumbinginterrogators.txt[]
 361
 362In general, the interrogate commands do not touch the files in
 363the working tree.
 364
 365
 366Synching repositories
 367~~~~~~~~~~~~~~~~~~~~~
 368
 369include::cmds-synchingrepositories.txt[]
 370
 371The following are helper commands used by the above; end users
 372typically do not use them directly.
 373
 374include::cmds-synchelpers.txt[]
 375
 376
 377Internal helper commands
 378~~~~~~~~~~~~~~~~~~~~~~~~
 379
 380These are internal helper commands used by other commands; end
 381users typically do not use them directly.
 382
 383include::cmds-purehelpers.txt[]
 384
 385
 386Configuration Mechanism
 387-----------------------
 388
 389Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 390is used to hold per-repository configuration options.  It is a
 391simple text file modeled after `.ini` format familiar to some
 392people.  Here is an example:
 393
 394------------
 395#
 396# A '#' or ';' character indicates a comment.
 397#
 398
 399; core variables
 400[core]
 401        ; Don't trust file modes
 402        filemode = false
 403
 404; user identity
 405[user]
 406        name = "Junio C Hamano"
 407        email = "junkio@twinsun.com"
 408
 409------------
 410
 411Various commands read from the configuration file and adjust
 412their operation accordingly.  See linkgit:git-config[1] for a
 413list.
 414
 415
 416Identifier Terminology
 417----------------------
 418<object>::
 419        Indicates the object name for any type of object.
 420
 421<blob>::
 422        Indicates a blob object name.
 423
 424<tree>::
 425        Indicates a tree object name.
 426
 427<commit>::
 428        Indicates a commit object name.
 429
 430<tree-ish>::
 431        Indicates a tree, commit or tag object name.  A
 432        command that takes a <tree-ish> argument ultimately wants to
 433        operate on a <tree> object but automatically dereferences
 434        <commit> and <tag> objects that point at a <tree>.
 435
 436<commit-ish>::
 437        Indicates a commit or tag object name.  A
 438        command that takes a <commit-ish> argument ultimately wants to
 439        operate on a <commit> object but automatically dereferences
 440        <tag> objects that point at a <commit>.
 441
 442<type>::
 443        Indicates that an object type is required.
 444        Currently one of: `blob`, `tree`, `commit`, or `tag`.
 445
 446<file>::
 447        Indicates a filename - almost always relative to the
 448        root of the tree structure `GIT_INDEX_FILE` describes.
 449
 450Symbolic Identifiers
 451--------------------
 452Any git command accepting any <object> can also use the following
 453symbolic notation:
 454
 455HEAD::
 456        indicates the head of the current branch (i.e. the
 457        contents of `$GIT_DIR/HEAD`).
 458
 459<tag>::
 460        a valid tag 'name'
 461        (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 462
 463<head>::
 464        a valid head 'name'
 465        (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 466
 467For a more complete list of ways to spell object names, see
 468"SPECIFYING REVISIONS" section in linkgit:git-rev-parse[1].
 469
 470
 471File/Directory Structure
 472------------------------
 473
 474Please see the linkgit:gitrepository-layout[5] document.
 475
 476Read linkgit:githooks[5] for more details about each hook.
 477
 478Higher level SCMs may provide and manage additional information in the
 479`$GIT_DIR`.
 480
 481
 482Terminology
 483-----------
 484Please see linkgit:gitglossary[7].
 485
 486
 487Environment Variables
 488---------------------
 489Various git commands use the following environment variables:
 490
 491The git Repository
 492~~~~~~~~~~~~~~~~~~
 493These environment variables apply to 'all' core git commands. Nb: it
 494is worth noting that they may be used/overridden by SCMS sitting above
 495git so take care if using Cogito etc.
 496
 497'GIT_INDEX_FILE'::
 498        This environment allows the specification of an alternate
 499        index file. If not specified, the default of `$GIT_DIR/index`
 500        is used.
 501
 502'GIT_OBJECT_DIRECTORY'::
 503        If the object storage directory is specified via this
 504        environment variable then the sha1 directories are created
 505        underneath - otherwise the default `$GIT_DIR/objects`
 506        directory is used.
 507
 508'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 509        Due to the immutable nature of git objects, old objects can be
 510        archived into shared, read-only directories. This variable
 511        specifies a ":" separated (on Windows ";" separated) list
 512        of git object directories which can be used to search for git
 513        objects. New objects will not be written to these directories.
 514
 515'GIT_DIR'::
 516        If the 'GIT_DIR' environment variable is set then it
 517        specifies a path to use instead of the default `.git`
 518        for the base of the repository.
 519
 520'GIT_WORK_TREE'::
 521        Set the path to the working tree.  The value will not be
 522        used in combination with repositories found automatically in
 523        a .git directory (i.e. $GIT_DIR is not set).
 524        This can also be controlled by the '--work-tree' command line
 525        option and the core.worktree configuration variable.
 526
 527'GIT_CEILING_DIRECTORIES'::
 528        This should be a colon-separated list of absolute paths.
 529        If set, it is a list of directories that git should not chdir
 530        up into while looking for a repository directory.
 531        It will not exclude the current working directory or
 532        a GIT_DIR set on the command line or in the environment.
 533        (Useful for excluding slow-loading network directories.)
 534
 535git Commits
 536~~~~~~~~~~~
 537'GIT_AUTHOR_NAME'::
 538'GIT_AUTHOR_EMAIL'::
 539'GIT_AUTHOR_DATE'::
 540'GIT_COMMITTER_NAME'::
 541'GIT_COMMITTER_EMAIL'::
 542'GIT_COMMITTER_DATE'::
 543'EMAIL'::
 544        see linkgit:git-commit-tree[1]
 545
 546git Diffs
 547~~~~~~~~~
 548'GIT_DIFF_OPTS'::
 549        Only valid setting is "--unified=??" or "-u??" to set the
 550        number of context lines shown when a unified diff is created.
 551        This takes precedence over any "-U" or "--unified" option
 552        value passed on the git diff command line.
 553
 554'GIT_EXTERNAL_DIFF'::
 555        When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 556        program named by it is called, instead of the diff invocation
 557        described above.  For a path that is added, removed, or modified,
 558        'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 559
 560        path old-file old-hex old-mode new-file new-hex new-mode
 561+
 562where:
 563
 564        <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 565                         contents of <old|new>,
 566        <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 567        <old|new>-mode:: are the octal representation of the file modes.
 568
 569+
 570The file parameters can point at the user's working file
 571(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 572when a new file is added), or a temporary file (e.g. `old-file` in the
 573index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 574temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 575+
 576For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 577parameter, <path>.
 578
 579other
 580~~~~~
 581'GIT_MERGE_VERBOSITY'::
 582        A number controlling the amount of output shown by
 583        the recursive merge strategy.  Overrides merge.verbosity.
 584        See linkgit:git-merge[1]
 585
 586'GIT_PAGER'::
 587        This environment variable overrides `$PAGER`. If it is set
 588        to an empty string or to the value "cat", git will not launch
 589        a pager.  See also the `core.pager` option in
 590        linkgit:git-config[1].
 591
 592'GIT_SSH'::
 593        If this environment variable is set then 'git fetch'
 594        and 'git push' will use this command instead
 595        of 'ssh' when they need to connect to a remote system.
 596        The '$GIT_SSH' command will be given exactly two arguments:
 597        the 'username@host' (or just 'host') from the URL and the
 598        shell command to execute on that remote system.
 599+
 600To pass options to the program that you want to list in GIT_SSH
 601you will need to wrap the program and options into a shell script,
 602then set GIT_SSH to refer to the shell script.
 603+
 604Usually it is easier to configure any desired options through your
 605personal `.ssh/config` file.  Please consult your ssh documentation
 606for further details.
 607
 608'GIT_FLUSH'::
 609        If this environment variable is set to "1", then commands such
 610        as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 611        and 'git whatchanged' will force a flush of the output stream
 612        after each commit-oriented record have been flushed.   If this
 613        variable is set to "0", the output of these commands will be done
 614        using completely buffered I/O.   If this environment variable is
 615        not set, git will choose buffered or record-oriented flushing
 616        based on whether stdout appears to be redirected to a file or not.
 617
 618'GIT_TRACE'::
 619        If this variable is set to "1", "2" or "true" (comparison
 620        is case insensitive), git will print `trace:` messages on
 621        stderr telling about alias expansion, built-in command
 622        execution and external command execution.
 623        If this variable is set to an integer value greater than 1
 624        and lower than 10 (strictly) then git will interpret this
 625        value as an open file descriptor and will try to write the
 626        trace messages into this file descriptor.
 627        Alternatively, if this variable is set to an absolute path
 628        (starting with a '/' character), git will interpret this
 629        as a file path and will try to write the trace messages
 630        into it.
 631
 632Discussion[[Discussion]]
 633------------------------
 634
 635More detail on the following is available from the
 636link:user-manual.html#git-concepts[git concepts chapter of the
 637user-manual] and linkgit:gitcore-tutorial[7].
 638
 639A git project normally consists of a working directory with a ".git"
 640subdirectory at the top level.  The .git directory contains, among other
 641things, a compressed object database representing the complete history
 642of the project, an "index" file which links that history to the current
 643contents of the working tree, and named pointers into that history such
 644as tags and branch heads.
 645
 646The object database contains objects of three main types: blobs, which
 647hold file data; trees, which point to blobs and other trees to build up
 648directory hierarchies; and commits, which each reference a single tree
 649and some number of parent commits.
 650
 651The commit, equivalent to what other systems call a "changeset" or
 652"version", represents a step in the project's history, and each parent
 653represents an immediately preceding step.  Commits with more than one
 654parent represent merges of independent lines of development.
 655
 656All objects are named by the SHA1 hash of their contents, normally
 657written as a string of 40 hex digits.  Such names are globally unique.
 658The entire history leading up to a commit can be vouched for by signing
 659just that commit.  A fourth object type, the tag, is provided for this
 660purpose.
 661
 662When first created, objects are stored in individual files, but for
 663efficiency may later be compressed together into "pack files".
 664
 665Named pointers called refs mark interesting points in history.  A ref
 666may contain the SHA1 name of an object or the name of another ref.  Refs
 667with names beginning `ref/head/` contain the SHA1 name of the most
 668recent commit (or "head") of a branch under development.  SHA1 names of
 669tags of interest are stored under `ref/tags/`.  A special ref named
 670`HEAD` contains the name of the currently checked-out branch.
 671
 672The index file is initialized with a list of all paths and, for each
 673path, a blob object and a set of attributes.  The blob object represents
 674the contents of the file as of the head of the current branch.  The
 675attributes (last modified time, size, etc.) are taken from the
 676corresponding file in the working tree.  Subsequent changes to the
 677working tree can be found by comparing these attributes.  The index may
 678be updated with new content, and new commits may be created from the
 679content stored in the index.
 680
 681The index is also capable of storing multiple entries (called "stages")
 682for a given pathname.  These stages are used to hold the various
 683unmerged version of a file when a merge is in progress.
 684
 685Authors
 686-------
 687* git's founding father is Linus Torvalds <torvalds@osdl.org>.
 688* The current git nurse is Junio C Hamano <gitster@pobox.com>.
 689* The git potty was written by Andreas Ericsson <ae@op5.se>.
 690* General upbringing is handled by the git-list <git@vger.kernel.org>.
 691
 692Documentation
 693--------------
 694The documentation for git suite was started by David Greaves
 695<david@dgreaves.com>, and later enhanced greatly by the
 696contributors on the git-list <git@vger.kernel.org>.
 697
 698SEE ALSO
 699--------
 700linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 701link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 702linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 703linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 704linkgit:gitworkflows[7]
 705
 706GIT
 707---
 708Part of the linkgit:git[1] suite