Documentation / git.txton commit Git 1.7.1.2 (245b10c)
   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
  47* link:v1.7.1.2/git.html[documentation for release 1.7.1.2]
  48
  49* release notes for
  50  link:RelNotes-1.7.1.2.txt[1.7.1.2],
  51  link:RelNotes-1.7.1.1.txt[1.7.1.1],
  52  link:RelNotes-1.7.1.txt[1.7.1].
  53
  54* link:v1.7.0.7/git.html[documentation for release 1.7.0.7]
  55
  56* release notes for
  57  link:RelNotes-1.7.0.7.txt[1.7.0.7],
  58  link:RelNotes-1.7.0.6.txt[1.7.0.6],
  59  link:RelNotes-1.7.0.5.txt[1.7.0.5],
  60  link:RelNotes-1.7.0.4.txt[1.7.0.4],
  61  link:RelNotes-1.7.0.3.txt[1.7.0.3],
  62  link:RelNotes-1.7.0.2.txt[1.7.0.2],
  63  link:RelNotes-1.7.0.1.txt[1.7.0.1],
  64  link:RelNotes-1.7.0.txt[1.7.0].
  65
  66* link:v1.6.6.2/git.html[documentation for release 1.6.6.2]
  67
  68* release notes for
  69  link:RelNotes-1.6.6.2.txt[1.6.6.2],
  70  link:RelNotes-1.6.6.1.txt[1.6.6.1],
  71  link:RelNotes-1.6.6.txt[1.6.6].
  72
  73* link:v1.6.5.8/git.html[documentation for release 1.6.5.8]
  74
  75* release notes for
  76  link:RelNotes-1.6.5.8.txt[1.6.5.8],
  77  link:RelNotes-1.6.5.7.txt[1.6.5.7],
  78  link:RelNotes-1.6.5.6.txt[1.6.5.6],
  79  link:RelNotes-1.6.5.5.txt[1.6.5.5],
  80  link:RelNotes-1.6.5.4.txt[1.6.5.4],
  81  link:RelNotes-1.6.5.3.txt[1.6.5.3],
  82  link:RelNotes-1.6.5.2.txt[1.6.5.2],
  83  link:RelNotes-1.6.5.1.txt[1.6.5.1],
  84  link:RelNotes-1.6.5.txt[1.6.5].
  85
  86* link:v1.6.4.4/git.html[documentation for release 1.6.4.4]
  87
  88* release notes for
  89  link:RelNotes-1.6.4.4.txt[1.6.4.4],
  90  link:RelNotes-1.6.4.3.txt[1.6.4.3],
  91  link:RelNotes-1.6.4.2.txt[1.6.4.2],
  92  link:RelNotes-1.6.4.1.txt[1.6.4.1],
  93  link:RelNotes-1.6.4.txt[1.6.4].
  94
  95* link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
  96
  97* release notes for
  98  link:RelNotes-1.6.3.4.txt[1.6.3.4],
  99  link:RelNotes-1.6.3.3.txt[1.6.3.3],
 100  link:RelNotes-1.6.3.2.txt[1.6.3.2],
 101  link:RelNotes-1.6.3.1.txt[1.6.3.1],
 102  link:RelNotes-1.6.3.txt[1.6.3].
 103
 104* release notes for
 105  link:RelNotes-1.6.2.5.txt[1.6.2.5],
 106  link:RelNotes-1.6.2.4.txt[1.6.2.4],
 107  link:RelNotes-1.6.2.3.txt[1.6.2.3],
 108  link:RelNotes-1.6.2.2.txt[1.6.2.2],
 109  link:RelNotes-1.6.2.1.txt[1.6.2.1],
 110  link:RelNotes-1.6.2.txt[1.6.2].
 111
 112* link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
 113
 114* release notes for
 115  link:RelNotes-1.6.1.3.txt[1.6.1.3],
 116  link:RelNotes-1.6.1.2.txt[1.6.1.2],
 117  link:RelNotes-1.6.1.1.txt[1.6.1.1],
 118  link:RelNotes-1.6.1.txt[1.6.1].
 119
 120* link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 121
 122* release notes for
 123  link:RelNotes-1.6.0.6.txt[1.6.0.6],
 124  link:RelNotes-1.6.0.5.txt[1.6.0.5],
 125  link:RelNotes-1.6.0.4.txt[1.6.0.4],
 126  link:RelNotes-1.6.0.3.txt[1.6.0.3],
 127  link:RelNotes-1.6.0.2.txt[1.6.0.2],
 128  link:RelNotes-1.6.0.1.txt[1.6.0.1],
 129  link:RelNotes-1.6.0.txt[1.6.0].
 130
 131* link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 132
 133* release notes for
 134  link:RelNotes-1.5.6.6.txt[1.5.6.6],
 135  link:RelNotes-1.5.6.5.txt[1.5.6.5],
 136  link:RelNotes-1.5.6.4.txt[1.5.6.4],
 137  link:RelNotes-1.5.6.3.txt[1.5.6.3],
 138  link:RelNotes-1.5.6.2.txt[1.5.6.2],
 139  link:RelNotes-1.5.6.1.txt[1.5.6.1],
 140  link:RelNotes-1.5.6.txt[1.5.6].
 141
 142* link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 143
 144* release notes for
 145  link:RelNotes-1.5.5.6.txt[1.5.5.6],
 146  link:RelNotes-1.5.5.5.txt[1.5.5.5],
 147  link:RelNotes-1.5.5.4.txt[1.5.5.4],
 148  link:RelNotes-1.5.5.3.txt[1.5.5.3],
 149  link:RelNotes-1.5.5.2.txt[1.5.5.2],
 150  link:RelNotes-1.5.5.1.txt[1.5.5.1],
 151  link:RelNotes-1.5.5.txt[1.5.5].
 152
 153* link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 154
 155* release notes for
 156  link:RelNotes-1.5.4.7.txt[1.5.4.7],
 157  link:RelNotes-1.5.4.6.txt[1.5.4.6],
 158  link:RelNotes-1.5.4.5.txt[1.5.4.5],
 159  link:RelNotes-1.5.4.4.txt[1.5.4.4],
 160  link:RelNotes-1.5.4.3.txt[1.5.4.3],
 161  link:RelNotes-1.5.4.2.txt[1.5.4.2],
 162  link:RelNotes-1.5.4.1.txt[1.5.4.1],
 163  link:RelNotes-1.5.4.txt[1.5.4].
 164
 165* link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 166
 167* release notes for
 168  link:RelNotes-1.5.3.8.txt[1.5.3.8],
 169  link:RelNotes-1.5.3.7.txt[1.5.3.7],
 170  link:RelNotes-1.5.3.6.txt[1.5.3.6],
 171  link:RelNotes-1.5.3.5.txt[1.5.3.5],
 172  link:RelNotes-1.5.3.4.txt[1.5.3.4],
 173  link:RelNotes-1.5.3.3.txt[1.5.3.3],
 174  link:RelNotes-1.5.3.2.txt[1.5.3.2],
 175  link:RelNotes-1.5.3.1.txt[1.5.3.1],
 176  link:RelNotes-1.5.3.txt[1.5.3].
 177
 178* link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 179
 180* release notes for
 181  link:RelNotes-1.5.2.5.txt[1.5.2.5],
 182  link:RelNotes-1.5.2.4.txt[1.5.2.4],
 183  link:RelNotes-1.5.2.3.txt[1.5.2.3],
 184  link:RelNotes-1.5.2.2.txt[1.5.2.2],
 185  link:RelNotes-1.5.2.1.txt[1.5.2.1],
 186  link:RelNotes-1.5.2.txt[1.5.2].
 187
 188* link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 189
 190* release notes for
 191  link:RelNotes-1.5.1.6.txt[1.5.1.6],
 192  link:RelNotes-1.5.1.5.txt[1.5.1.5],
 193  link:RelNotes-1.5.1.4.txt[1.5.1.4],
 194  link:RelNotes-1.5.1.3.txt[1.5.1.3],
 195  link:RelNotes-1.5.1.2.txt[1.5.1.2],
 196  link:RelNotes-1.5.1.1.txt[1.5.1.1],
 197  link:RelNotes-1.5.1.txt[1.5.1].
 198
 199* link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 200
 201* release notes for
 202  link:RelNotes-1.5.0.7.txt[1.5.0.7],
 203  link:RelNotes-1.5.0.6.txt[1.5.0.6],
 204  link:RelNotes-1.5.0.5.txt[1.5.0.5],
 205  link:RelNotes-1.5.0.3.txt[1.5.0.3],
 206  link:RelNotes-1.5.0.2.txt[1.5.0.2],
 207  link:RelNotes-1.5.0.1.txt[1.5.0.1],
 208  link:RelNotes-1.5.0.txt[1.5.0].
 209
 210* documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 211  link:v1.3.3/git.html[1.3.3],
 212  link:v1.2.6/git.html[1.2.6],
 213  link:v1.0.13/git.html[1.0.13].
 214
 215============
 216
 217endif::stalenotes[]
 218
 219OPTIONS
 220-------
 221--version::
 222        Prints the git suite version that the 'git' program came from.
 223
 224--help::
 225        Prints the synopsis and a list of the most commonly used
 226        commands. If the option '--all' or '-a' is given then all
 227        available commands are printed. If a git command is named this
 228        option will bring up the manual page for that command.
 229+
 230Other options are available to control how the manual page is
 231displayed. See linkgit:git-help[1] for more information,
 232because `git --help ...` is converted internally into `git
 233help ...`.
 234
 235--exec-path::
 236        Path to wherever your core git programs are installed.
 237        This can also be controlled by setting the GIT_EXEC_PATH
 238        environment variable. If no path is given, 'git' will print
 239        the current setting and then exit.
 240
 241--html-path::
 242        Print the path to wherever your git HTML documentation is installed
 243        and exit.
 244
 245-p::
 246--paginate::
 247        Pipe all output into 'less' (or if set, $PAGER) if standard
 248        output is a terminal.  This overrides the `pager.<cmd>`
 249        configuration options (see the "Configuration Mechanism" section
 250        below).
 251
 252--no-pager::
 253        Do not pipe git output into a pager.
 254
 255--git-dir=<path>::
 256        Set the path to the repository. This can also be controlled by
 257        setting the GIT_DIR environment variable. It can be an absolute
 258        path or relative path to current working directory.
 259
 260--work-tree=<path>::
 261        Set the path to the working tree.  The value will not be
 262        used in combination with repositories found automatically in
 263        a .git directory (i.e. $GIT_DIR is not set).
 264        This can also be controlled by setting the GIT_WORK_TREE
 265        environment variable and the core.worktree configuration
 266        variable. It can be an absolute path or relative path to
 267        the directory specified by --git-dir or GIT_DIR.
 268        Note: If --git-dir or GIT_DIR are specified but none of
 269        --work-tree, GIT_WORK_TREE and core.worktree is specified,
 270        the current working directory is regarded as the top directory
 271        of your working tree.
 272
 273--bare::
 274        Treat the repository as a bare repository.  If GIT_DIR
 275        environment is not set, it is set to the current working
 276        directory.
 277
 278--no-replace-objects::
 279        Do not use replacement refs to replace git objects. See
 280        linkgit:git-replace[1] for more information.
 281
 282
 283FURTHER DOCUMENTATION
 284---------------------
 285
 286See the references above to get started using git.  The following is
 287probably more detail than necessary for a first-time user.
 288
 289The link:user-manual.html#git-concepts[git concepts chapter of the
 290user-manual] and linkgit:gitcore-tutorial[7] both provide
 291introductions to the underlying git architecture.
 292
 293See linkgit:gitworkflows[7] for an overview of recommended workflows.
 294
 295See also the link:howto-index.html[howto] documents for some useful
 296examples.
 297
 298The internals are documented in the
 299link:technical/api-index.html[GIT API documentation].
 300
 301GIT COMMANDS
 302------------
 303
 304We divide git into high level ("porcelain") commands and low level
 305("plumbing") commands.
 306
 307High-level commands (porcelain)
 308-------------------------------
 309
 310We separate the porcelain commands into the main commands and some
 311ancillary user utilities.
 312
 313Main porcelain commands
 314~~~~~~~~~~~~~~~~~~~~~~~
 315
 316include::cmds-mainporcelain.txt[]
 317
 318Ancillary Commands
 319~~~~~~~~~~~~~~~~~~
 320Manipulators:
 321
 322include::cmds-ancillarymanipulators.txt[]
 323
 324Interrogators:
 325
 326include::cmds-ancillaryinterrogators.txt[]
 327
 328
 329Interacting with Others
 330~~~~~~~~~~~~~~~~~~~~~~~
 331
 332These commands are to interact with foreign SCM and with other
 333people via patch over e-mail.
 334
 335include::cmds-foreignscminterface.txt[]
 336
 337
 338Low-level commands (plumbing)
 339-----------------------------
 340
 341Although git includes its
 342own porcelain layer, its low-level commands are sufficient to support
 343development of alternative porcelains.  Developers of such porcelains
 344might start by reading about linkgit:git-update-index[1] and
 345linkgit:git-read-tree[1].
 346
 347The interface (input, output, set of options and the semantics)
 348to these low-level commands are meant to be a lot more stable
 349than Porcelain level commands, because these commands are
 350primarily for scripted use.  The interface to Porcelain commands
 351on the other hand are subject to change in order to improve the
 352end user experience.
 353
 354The following description divides
 355the low-level commands into commands that manipulate objects (in
 356the repository, index, and working tree), commands that interrogate and
 357compare objects, and commands that move objects and references between
 358repositories.
 359
 360
 361Manipulation commands
 362~~~~~~~~~~~~~~~~~~~~~
 363
 364include::cmds-plumbingmanipulators.txt[]
 365
 366
 367Interrogation commands
 368~~~~~~~~~~~~~~~~~~~~~~
 369
 370include::cmds-plumbinginterrogators.txt[]
 371
 372In general, the interrogate commands do not touch the files in
 373the working tree.
 374
 375
 376Synching repositories
 377~~~~~~~~~~~~~~~~~~~~~
 378
 379include::cmds-synchingrepositories.txt[]
 380
 381The following are helper commands used by the above; end users
 382typically do not use them directly.
 383
 384include::cmds-synchelpers.txt[]
 385
 386
 387Internal helper commands
 388~~~~~~~~~~~~~~~~~~~~~~~~
 389
 390These are internal helper commands used by other commands; end
 391users typically do not use them directly.
 392
 393include::cmds-purehelpers.txt[]
 394
 395
 396Configuration Mechanism
 397-----------------------
 398
 399Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 400is used to hold per-repository configuration options.  It is a
 401simple text file modeled after `.ini` format familiar to some
 402people.  Here is an example:
 403
 404------------
 405#
 406# A '#' or ';' character indicates a comment.
 407#
 408
 409; core variables
 410[core]
 411        ; Don't trust file modes
 412        filemode = false
 413
 414; user identity
 415[user]
 416        name = "Junio C Hamano"
 417        email = "junkio@twinsun.com"
 418
 419------------
 420
 421Various commands read from the configuration file and adjust
 422their operation accordingly.  See linkgit:git-config[1] for a
 423list.
 424
 425
 426Identifier Terminology
 427----------------------
 428<object>::
 429        Indicates the object name for any type of object.
 430
 431<blob>::
 432        Indicates a blob object name.
 433
 434<tree>::
 435        Indicates a tree object name.
 436
 437<commit>::
 438        Indicates a commit object name.
 439
 440<tree-ish>::
 441        Indicates a tree, commit or tag object name.  A
 442        command that takes a <tree-ish> argument ultimately wants to
 443        operate on a <tree> object but automatically dereferences
 444        <commit> and <tag> objects that point at a <tree>.
 445
 446<commit-ish>::
 447        Indicates a commit or tag object name.  A
 448        command that takes a <commit-ish> argument ultimately wants to
 449        operate on a <commit> object but automatically dereferences
 450        <tag> objects that point at a <commit>.
 451
 452<type>::
 453        Indicates that an object type is required.
 454        Currently one of: `blob`, `tree`, `commit`, or `tag`.
 455
 456<file>::
 457        Indicates a filename - almost always relative to the
 458        root of the tree structure `GIT_INDEX_FILE` describes.
 459
 460Symbolic Identifiers
 461--------------------
 462Any git command accepting any <object> can also use the following
 463symbolic notation:
 464
 465HEAD::
 466        indicates the head of the current branch (i.e. the
 467        contents of `$GIT_DIR/HEAD`).
 468
 469<tag>::
 470        a valid tag 'name'
 471        (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 472
 473<head>::
 474        a valid head 'name'
 475        (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 476
 477For a more complete list of ways to spell object names, see
 478"SPECIFYING REVISIONS" section in linkgit:git-rev-parse[1].
 479
 480
 481File/Directory Structure
 482------------------------
 483
 484Please see the linkgit:gitrepository-layout[5] document.
 485
 486Read linkgit:githooks[5] for more details about each hook.
 487
 488Higher level SCMs may provide and manage additional information in the
 489`$GIT_DIR`.
 490
 491
 492Terminology
 493-----------
 494Please see linkgit:gitglossary[7].
 495
 496
 497Environment Variables
 498---------------------
 499Various git commands use the following environment variables:
 500
 501The git Repository
 502~~~~~~~~~~~~~~~~~~
 503These environment variables apply to 'all' core git commands. Nb: it
 504is worth noting that they may be used/overridden by SCMS sitting above
 505git so take care if using Cogito etc.
 506
 507'GIT_INDEX_FILE'::
 508        This environment allows the specification of an alternate
 509        index file. If not specified, the default of `$GIT_DIR/index`
 510        is used.
 511
 512'GIT_OBJECT_DIRECTORY'::
 513        If the object storage directory is specified via this
 514        environment variable then the sha1 directories are created
 515        underneath - otherwise the default `$GIT_DIR/objects`
 516        directory is used.
 517
 518'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 519        Due to the immutable nature of git objects, old objects can be
 520        archived into shared, read-only directories. This variable
 521        specifies a ":" separated (on Windows ";" separated) list
 522        of git object directories which can be used to search for git
 523        objects. New objects will not be written to these directories.
 524
 525'GIT_DIR'::
 526        If the 'GIT_DIR' environment variable is set then it
 527        specifies a path to use instead of the default `.git`
 528        for the base of the repository.
 529
 530'GIT_WORK_TREE'::
 531        Set the path to the working tree.  The value will not be
 532        used in combination with repositories found automatically in
 533        a .git directory (i.e. $GIT_DIR is not set).
 534        This can also be controlled by the '--work-tree' command line
 535        option and the core.worktree configuration variable.
 536
 537'GIT_CEILING_DIRECTORIES'::
 538        This should be a colon-separated list of absolute paths.
 539        If set, it is a list of directories that git should not chdir
 540        up into while looking for a repository directory.
 541        It will not exclude the current working directory or
 542        a GIT_DIR set on the command line or in the environment.
 543        (Useful for excluding slow-loading network directories.)
 544
 545git Commits
 546~~~~~~~~~~~
 547'GIT_AUTHOR_NAME'::
 548'GIT_AUTHOR_EMAIL'::
 549'GIT_AUTHOR_DATE'::
 550'GIT_COMMITTER_NAME'::
 551'GIT_COMMITTER_EMAIL'::
 552'GIT_COMMITTER_DATE'::
 553'EMAIL'::
 554        see linkgit:git-commit-tree[1]
 555
 556git Diffs
 557~~~~~~~~~
 558'GIT_DIFF_OPTS'::
 559        Only valid setting is "--unified=??" or "-u??" to set the
 560        number of context lines shown when a unified diff is created.
 561        This takes precedence over any "-U" or "--unified" option
 562        value passed on the git diff command line.
 563
 564'GIT_EXTERNAL_DIFF'::
 565        When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 566        program named by it is called, instead of the diff invocation
 567        described above.  For a path that is added, removed, or modified,
 568        'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 569
 570        path old-file old-hex old-mode new-file new-hex new-mode
 571+
 572where:
 573
 574        <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 575                         contents of <old|new>,
 576        <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 577        <old|new>-mode:: are the octal representation of the file modes.
 578
 579+
 580The file parameters can point at the user's working file
 581(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 582when a new file is added), or a temporary file (e.g. `old-file` in the
 583index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 584temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 585+
 586For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 587parameter, <path>.
 588
 589other
 590~~~~~
 591'GIT_MERGE_VERBOSITY'::
 592        A number controlling the amount of output shown by
 593        the recursive merge strategy.  Overrides merge.verbosity.
 594        See linkgit:git-merge[1]
 595
 596'GIT_PAGER'::
 597        This environment variable overrides `$PAGER`. If it is set
 598        to an empty string or to the value "cat", git will not launch
 599        a pager.  See also the `core.pager` option in
 600        linkgit:git-config[1].
 601
 602'GIT_SSH'::
 603        If this environment variable is set then 'git fetch'
 604        and 'git push' will use this command instead
 605        of 'ssh' when they need to connect to a remote system.
 606        The '$GIT_SSH' command will be given exactly two arguments:
 607        the 'username@host' (or just 'host') from the URL and the
 608        shell command to execute on that remote system.
 609+
 610To pass options to the program that you want to list in GIT_SSH
 611you will need to wrap the program and options into a shell script,
 612then set GIT_SSH to refer to the shell script.
 613+
 614Usually it is easier to configure any desired options through your
 615personal `.ssh/config` file.  Please consult your ssh documentation
 616for further details.
 617
 618'GIT_FLUSH'::
 619        If this environment variable is set to "1", then commands such
 620        as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 621        and 'git whatchanged' will force a flush of the output stream
 622        after each commit-oriented record have been flushed.   If this
 623        variable is set to "0", the output of these commands will be done
 624        using completely buffered I/O.   If this environment variable is
 625        not set, git will choose buffered or record-oriented flushing
 626        based on whether stdout appears to be redirected to a file or not.
 627
 628'GIT_TRACE'::
 629        If this variable is set to "1", "2" or "true" (comparison
 630        is case insensitive), git will print `trace:` messages on
 631        stderr telling about alias expansion, built-in command
 632        execution and external command execution.
 633        If this variable is set to an integer value greater than 1
 634        and lower than 10 (strictly) then git will interpret this
 635        value as an open file descriptor and will try to write the
 636        trace messages into this file descriptor.
 637        Alternatively, if this variable is set to an absolute path
 638        (starting with a '/' character), git will interpret this
 639        as a file path and will try to write the trace messages
 640        into it.
 641
 642Discussion[[Discussion]]
 643------------------------
 644
 645More detail on the following is available from the
 646link:user-manual.html#git-concepts[git concepts chapter of the
 647user-manual] and linkgit:gitcore-tutorial[7].
 648
 649A git project normally consists of a working directory with a ".git"
 650subdirectory at the top level.  The .git directory contains, among other
 651things, a compressed object database representing the complete history
 652of the project, an "index" file which links that history to the current
 653contents of the working tree, and named pointers into that history such
 654as tags and branch heads.
 655
 656The object database contains objects of three main types: blobs, which
 657hold file data; trees, which point to blobs and other trees to build up
 658directory hierarchies; and commits, which each reference a single tree
 659and some number of parent commits.
 660
 661The commit, equivalent to what other systems call a "changeset" or
 662"version", represents a step in the project's history, and each parent
 663represents an immediately preceding step.  Commits with more than one
 664parent represent merges of independent lines of development.
 665
 666All objects are named by the SHA1 hash of their contents, normally
 667written as a string of 40 hex digits.  Such names are globally unique.
 668The entire history leading up to a commit can be vouched for by signing
 669just that commit.  A fourth object type, the tag, is provided for this
 670purpose.
 671
 672When first created, objects are stored in individual files, but for
 673efficiency may later be compressed together into "pack files".
 674
 675Named pointers called refs mark interesting points in history.  A ref
 676may contain the SHA1 name of an object or the name of another ref.  Refs
 677with names beginning `ref/head/` contain the SHA1 name of the most
 678recent commit (or "head") of a branch under development.  SHA1 names of
 679tags of interest are stored under `ref/tags/`.  A special ref named
 680`HEAD` contains the name of the currently checked-out branch.
 681
 682The index file is initialized with a list of all paths and, for each
 683path, a blob object and a set of attributes.  The blob object represents
 684the contents of the file as of the head of the current branch.  The
 685attributes (last modified time, size, etc.) are taken from the
 686corresponding file in the working tree.  Subsequent changes to the
 687working tree can be found by comparing these attributes.  The index may
 688be updated with new content, and new commits may be created from the
 689content stored in the index.
 690
 691The index is also capable of storing multiple entries (called "stages")
 692for a given pathname.  These stages are used to hold the various
 693unmerged version of a file when a merge is in progress.
 694
 695Authors
 696-------
 697* git's founding father is Linus Torvalds <torvalds@osdl.org>.
 698* The current git nurse is Junio C Hamano <gitster@pobox.com>.
 699* The git potty was written by Andreas Ericsson <ae@op5.se>.
 700* General upbringing is handled by the git-list <git@vger.kernel.org>.
 701
 702Documentation
 703--------------
 704The documentation for git suite was started by David Greaves
 705<david@dgreaves.com>, and later enhanced greatly by the
 706contributors on the git-list <git@vger.kernel.org>.
 707
 708SEE ALSO
 709--------
 710linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 711link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 712linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 713linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 714linkgit:gitworkflows[7]
 715
 716GIT
 717---
 718Part of the linkgit:git[1] suite