Documentation / git.txton commit Merge branch 'pc/remove-warn' (3ecaa3b)
   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:v1.7.1/git.html[documentation for release 1.7.1]
  47
  48* release notes for
  49  link:RelNotes-1.7.1.txt[1.7.1].
  50
  51* link:v1.7.0.6/git.html[documentation for release 1.7.0.6]
  52
  53* release notes for
  54  link:RelNotes-1.7.0.6.txt[1.7.0.6],
  55  link:RelNotes-1.7.0.5.txt[1.7.0.5],
  56  link:RelNotes-1.7.0.4.txt[1.7.0.4],
  57  link:RelNotes-1.7.0.3.txt[1.7.0.3],
  58  link:RelNotes-1.7.0.2.txt[1.7.0.2],
  59  link:RelNotes-1.7.0.1.txt[1.7.0.1],
  60  link:RelNotes-1.7.0.txt[1.7.0].
  61
  62* link:v1.6.6.2/git.html[documentation for release 1.6.6.2]
  63
  64* release notes for
  65  link:RelNotes-1.6.6.2.txt[1.6.6.2],
  66  link:RelNotes-1.6.6.1.txt[1.6.6.1],
  67  link:RelNotes-1.6.6.txt[1.6.6].
  68
  69* link:v1.6.5.8/git.html[documentation for release 1.6.5.8]
  70
  71* release notes for
  72  link:RelNotes-1.6.5.8.txt[1.6.5.8],
  73  link:RelNotes-1.6.5.7.txt[1.6.5.7],
  74  link:RelNotes-1.6.5.6.txt[1.6.5.6],
  75  link:RelNotes-1.6.5.5.txt[1.6.5.5],
  76  link:RelNotes-1.6.5.4.txt[1.6.5.4],
  77  link:RelNotes-1.6.5.3.txt[1.6.5.3],
  78  link:RelNotes-1.6.5.2.txt[1.6.5.2],
  79  link:RelNotes-1.6.5.1.txt[1.6.5.1],
  80  link:RelNotes-1.6.5.txt[1.6.5].
  81
  82* link:v1.6.4.4/git.html[documentation for release 1.6.4.4]
  83
  84* release notes for
  85  link:RelNotes-1.6.4.4.txt[1.6.4.4],
  86  link:RelNotes-1.6.4.3.txt[1.6.4.3],
  87  link:RelNotes-1.6.4.2.txt[1.6.4.2],
  88  link:RelNotes-1.6.4.1.txt[1.6.4.1],
  89  link:RelNotes-1.6.4.txt[1.6.4].
  90
  91* link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
  92
  93* release notes for
  94  link:RelNotes-1.6.3.4.txt[1.6.3.4],
  95  link:RelNotes-1.6.3.3.txt[1.6.3.3],
  96  link:RelNotes-1.6.3.2.txt[1.6.3.2],
  97  link:RelNotes-1.6.3.1.txt[1.6.3.1],
  98  link:RelNotes-1.6.3.txt[1.6.3].
  99
 100* release notes for
 101  link:RelNotes-1.6.2.5.txt[1.6.2.5],
 102  link:RelNotes-1.6.2.4.txt[1.6.2.4],
 103  link:RelNotes-1.6.2.3.txt[1.6.2.3],
 104  link:RelNotes-1.6.2.2.txt[1.6.2.2],
 105  link:RelNotes-1.6.2.1.txt[1.6.2.1],
 106  link:RelNotes-1.6.2.txt[1.6.2].
 107
 108* link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
 109
 110* release notes for
 111  link:RelNotes-1.6.1.3.txt[1.6.1.3],
 112  link:RelNotes-1.6.1.2.txt[1.6.1.2],
 113  link:RelNotes-1.6.1.1.txt[1.6.1.1],
 114  link:RelNotes-1.6.1.txt[1.6.1].
 115
 116* link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 117
 118* release notes for
 119  link:RelNotes-1.6.0.6.txt[1.6.0.6],
 120  link:RelNotes-1.6.0.5.txt[1.6.0.5],
 121  link:RelNotes-1.6.0.4.txt[1.6.0.4],
 122  link:RelNotes-1.6.0.3.txt[1.6.0.3],
 123  link:RelNotes-1.6.0.2.txt[1.6.0.2],
 124  link:RelNotes-1.6.0.1.txt[1.6.0.1],
 125  link:RelNotes-1.6.0.txt[1.6.0].
 126
 127* link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 128
 129* release notes for
 130  link:RelNotes-1.5.6.6.txt[1.5.6.6],
 131  link:RelNotes-1.5.6.5.txt[1.5.6.5],
 132  link:RelNotes-1.5.6.4.txt[1.5.6.4],
 133  link:RelNotes-1.5.6.3.txt[1.5.6.3],
 134  link:RelNotes-1.5.6.2.txt[1.5.6.2],
 135  link:RelNotes-1.5.6.1.txt[1.5.6.1],
 136  link:RelNotes-1.5.6.txt[1.5.6].
 137
 138* link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 139
 140* release notes for
 141  link:RelNotes-1.5.5.6.txt[1.5.5.6],
 142  link:RelNotes-1.5.5.5.txt[1.5.5.5],
 143  link:RelNotes-1.5.5.4.txt[1.5.5.4],
 144  link:RelNotes-1.5.5.3.txt[1.5.5.3],
 145  link:RelNotes-1.5.5.2.txt[1.5.5.2],
 146  link:RelNotes-1.5.5.1.txt[1.5.5.1],
 147  link:RelNotes-1.5.5.txt[1.5.5].
 148
 149* link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 150
 151* release notes for
 152  link:RelNotes-1.5.4.7.txt[1.5.4.7],
 153  link:RelNotes-1.5.4.6.txt[1.5.4.6],
 154  link:RelNotes-1.5.4.5.txt[1.5.4.5],
 155  link:RelNotes-1.5.4.4.txt[1.5.4.4],
 156  link:RelNotes-1.5.4.3.txt[1.5.4.3],
 157  link:RelNotes-1.5.4.2.txt[1.5.4.2],
 158  link:RelNotes-1.5.4.1.txt[1.5.4.1],
 159  link:RelNotes-1.5.4.txt[1.5.4].
 160
 161* link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 162
 163* release notes for
 164  link:RelNotes-1.5.3.8.txt[1.5.3.8],
 165  link:RelNotes-1.5.3.7.txt[1.5.3.7],
 166  link:RelNotes-1.5.3.6.txt[1.5.3.6],
 167  link:RelNotes-1.5.3.5.txt[1.5.3.5],
 168  link:RelNotes-1.5.3.4.txt[1.5.3.4],
 169  link:RelNotes-1.5.3.3.txt[1.5.3.3],
 170  link:RelNotes-1.5.3.2.txt[1.5.3.2],
 171  link:RelNotes-1.5.3.1.txt[1.5.3.1],
 172  link:RelNotes-1.5.3.txt[1.5.3].
 173
 174* link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 175
 176* release notes for
 177  link:RelNotes-1.5.2.5.txt[1.5.2.5],
 178  link:RelNotes-1.5.2.4.txt[1.5.2.4],
 179  link:RelNotes-1.5.2.3.txt[1.5.2.3],
 180  link:RelNotes-1.5.2.2.txt[1.5.2.2],
 181  link:RelNotes-1.5.2.1.txt[1.5.2.1],
 182  link:RelNotes-1.5.2.txt[1.5.2].
 183
 184* link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 185
 186* release notes for
 187  link:RelNotes-1.5.1.6.txt[1.5.1.6],
 188  link:RelNotes-1.5.1.5.txt[1.5.1.5],
 189  link:RelNotes-1.5.1.4.txt[1.5.1.4],
 190  link:RelNotes-1.5.1.3.txt[1.5.1.3],
 191  link:RelNotes-1.5.1.2.txt[1.5.1.2],
 192  link:RelNotes-1.5.1.1.txt[1.5.1.1],
 193  link:RelNotes-1.5.1.txt[1.5.1].
 194
 195* link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 196
 197* release notes for
 198  link:RelNotes-1.5.0.7.txt[1.5.0.7],
 199  link:RelNotes-1.5.0.6.txt[1.5.0.6],
 200  link:RelNotes-1.5.0.5.txt[1.5.0.5],
 201  link:RelNotes-1.5.0.3.txt[1.5.0.3],
 202  link:RelNotes-1.5.0.2.txt[1.5.0.2],
 203  link:RelNotes-1.5.0.1.txt[1.5.0.1],
 204  link:RelNotes-1.5.0.txt[1.5.0].
 205
 206* documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 207  link:v1.3.3/git.html[1.3.3],
 208  link:v1.2.6/git.html[1.2.6],
 209  link:v1.0.13/git.html[1.0.13].
 210
 211============
 212
 213endif::stalenotes[]
 214
 215OPTIONS
 216-------
 217--version::
 218        Prints the git suite version that the 'git' program came from.
 219
 220--help::
 221        Prints the synopsis and a list of the most commonly used
 222        commands. If the option '--all' or '-a' is given then all
 223        available commands are printed. If a git command is named this
 224        option will bring up the manual page for that command.
 225+
 226Other options are available to control how the manual page is
 227displayed. See linkgit:git-help[1] for more information,
 228because `git --help ...` is converted internally into `git
 229help ...`.
 230
 231--exec-path::
 232        Path to wherever your core git programs are installed.
 233        This can also be controlled by setting the GIT_EXEC_PATH
 234        environment variable. If no path is given, 'git' will print
 235        the current setting and then exit.
 236
 237--html-path::
 238        Print the path to wherever your git HTML documentation is installed
 239        and exit.
 240
 241-p::
 242--paginate::
 243        Pipe all output into 'less' (or if set, $PAGER) if standard
 244        output is a terminal.  This overrides the `pager.<cmd>`
 245        configuration options (see the "Configuration Mechanism" section
 246        below).
 247
 248--no-pager::
 249        Do not pipe git output into a pager.
 250
 251--git-dir=<path>::
 252        Set the path to the repository. This can also be controlled by
 253        setting the GIT_DIR environment variable. It can be an absolute
 254        path or relative path to current working directory.
 255
 256--work-tree=<path>::
 257        Set the path to the working tree.  The value will not be
 258        used in combination with repositories found automatically in
 259        a .git directory (i.e. $GIT_DIR is not set).
 260        This can also be controlled by setting the GIT_WORK_TREE
 261        environment variable and the core.worktree configuration
 262        variable. It can be an absolute path or relative path to
 263        the directory specified by --git-dir or GIT_DIR.
 264        Note: If --git-dir or GIT_DIR are specified but none of
 265        --work-tree, GIT_WORK_TREE and core.worktree is specified,
 266        the current working directory is regarded as the top directory
 267        of your working tree.
 268
 269--bare::
 270        Treat the repository as a bare repository.  If GIT_DIR
 271        environment is not set, it is set to the current working
 272        directory.
 273
 274--no-replace-objects::
 275        Do not use replacement refs to replace git objects. See
 276        linkgit:git-replace[1] for more information.
 277
 278
 279FURTHER DOCUMENTATION
 280---------------------
 281
 282See the references above to get started using git.  The following is
 283probably more detail than necessary for a first-time user.
 284
 285The link:user-manual.html#git-concepts[git concepts chapter of the
 286user-manual] and linkgit:gitcore-tutorial[7] both provide
 287introductions to the underlying git architecture.
 288
 289See linkgit:gitworkflows[7] for an overview of recommended workflows.
 290
 291See also the link:howto-index.html[howto] documents for some useful
 292examples.
 293
 294The internals are documented in the
 295link:technical/api-index.html[GIT API documentation].
 296
 297GIT COMMANDS
 298------------
 299
 300We divide git into high level ("porcelain") commands and low level
 301("plumbing") commands.
 302
 303High-level commands (porcelain)
 304-------------------------------
 305
 306We separate the porcelain commands into the main commands and some
 307ancillary user utilities.
 308
 309Main porcelain commands
 310~~~~~~~~~~~~~~~~~~~~~~~
 311
 312include::cmds-mainporcelain.txt[]
 313
 314Ancillary Commands
 315~~~~~~~~~~~~~~~~~~
 316Manipulators:
 317
 318include::cmds-ancillarymanipulators.txt[]
 319
 320Interrogators:
 321
 322include::cmds-ancillaryinterrogators.txt[]
 323
 324
 325Interacting with Others
 326~~~~~~~~~~~~~~~~~~~~~~~
 327
 328These commands are to interact with foreign SCM and with other
 329people via patch over e-mail.
 330
 331include::cmds-foreignscminterface.txt[]
 332
 333
 334Low-level commands (plumbing)
 335-----------------------------
 336
 337Although git includes its
 338own porcelain layer, its low-level commands are sufficient to support
 339development of alternative porcelains.  Developers of such porcelains
 340might start by reading about linkgit:git-update-index[1] and
 341linkgit:git-read-tree[1].
 342
 343The interface (input, output, set of options and the semantics)
 344to these low-level commands are meant to be a lot more stable
 345than Porcelain level commands, because these commands are
 346primarily for scripted use.  The interface to Porcelain commands
 347on the other hand are subject to change in order to improve the
 348end user experience.
 349
 350The following description divides
 351the low-level commands into commands that manipulate objects (in
 352the repository, index, and working tree), commands that interrogate and
 353compare objects, and commands that move objects and references between
 354repositories.
 355
 356
 357Manipulation commands
 358~~~~~~~~~~~~~~~~~~~~~
 359
 360include::cmds-plumbingmanipulators.txt[]
 361
 362
 363Interrogation commands
 364~~~~~~~~~~~~~~~~~~~~~~
 365
 366include::cmds-plumbinginterrogators.txt[]
 367
 368In general, the interrogate commands do not touch the files in
 369the working tree.
 370
 371
 372Synching repositories
 373~~~~~~~~~~~~~~~~~~~~~
 374
 375include::cmds-synchingrepositories.txt[]
 376
 377The following are helper commands used by the above; end users
 378typically do not use them directly.
 379
 380include::cmds-synchelpers.txt[]
 381
 382
 383Internal helper commands
 384~~~~~~~~~~~~~~~~~~~~~~~~
 385
 386These are internal helper commands used by other commands; end
 387users typically do not use them directly.
 388
 389include::cmds-purehelpers.txt[]
 390
 391
 392Configuration Mechanism
 393-----------------------
 394
 395Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 396is used to hold per-repository configuration options.  It is a
 397simple text file modeled after `.ini` format familiar to some
 398people.  Here is an example:
 399
 400------------
 401#
 402# A '#' or ';' character indicates a comment.
 403#
 404
 405; core variables
 406[core]
 407        ; Don't trust file modes
 408        filemode = false
 409
 410; user identity
 411[user]
 412        name = "Junio C Hamano"
 413        email = "junkio@twinsun.com"
 414
 415------------
 416
 417Various commands read from the configuration file and adjust
 418their operation accordingly.  See linkgit:git-config[1] for a
 419list.
 420
 421
 422Identifier Terminology
 423----------------------
 424<object>::
 425        Indicates the object name for any type of object.
 426
 427<blob>::
 428        Indicates a blob object name.
 429
 430<tree>::
 431        Indicates a tree object name.
 432
 433<commit>::
 434        Indicates a commit object name.
 435
 436<tree-ish>::
 437        Indicates a tree, commit or tag object name.  A
 438        command that takes a <tree-ish> argument ultimately wants to
 439        operate on a <tree> object but automatically dereferences
 440        <commit> and <tag> objects that point at a <tree>.
 441
 442<commit-ish>::
 443        Indicates a commit or tag object name.  A
 444        command that takes a <commit-ish> argument ultimately wants to
 445        operate on a <commit> object but automatically dereferences
 446        <tag> objects that point at a <commit>.
 447
 448<type>::
 449        Indicates that an object type is required.
 450        Currently one of: `blob`, `tree`, `commit`, or `tag`.
 451
 452<file>::
 453        Indicates a filename - almost always relative to the
 454        root of the tree structure `GIT_INDEX_FILE` describes.
 455
 456Symbolic Identifiers
 457--------------------
 458Any git command accepting any <object> can also use the following
 459symbolic notation:
 460
 461HEAD::
 462        indicates the head of the current branch (i.e. the
 463        contents of `$GIT_DIR/HEAD`).
 464
 465<tag>::
 466        a valid tag 'name'
 467        (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 468
 469<head>::
 470        a valid head 'name'
 471        (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 472
 473For a more complete list of ways to spell object names, see
 474"SPECIFYING REVISIONS" section in linkgit:git-rev-parse[1].
 475
 476
 477File/Directory Structure
 478------------------------
 479
 480Please see the linkgit:gitrepository-layout[5] document.
 481
 482Read linkgit:githooks[5] for more details about each hook.
 483
 484Higher level SCMs may provide and manage additional information in the
 485`$GIT_DIR`.
 486
 487
 488Terminology
 489-----------
 490Please see linkgit:gitglossary[7].
 491
 492
 493Environment Variables
 494---------------------
 495Various git commands use the following environment variables:
 496
 497The git Repository
 498~~~~~~~~~~~~~~~~~~
 499These environment variables apply to 'all' core git commands. Nb: it
 500is worth noting that they may be used/overridden by SCMS sitting above
 501git so take care if using Cogito etc.
 502
 503'GIT_INDEX_FILE'::
 504        This environment allows the specification of an alternate
 505        index file. If not specified, the default of `$GIT_DIR/index`
 506        is used.
 507
 508'GIT_OBJECT_DIRECTORY'::
 509        If the object storage directory is specified via this
 510        environment variable then the sha1 directories are created
 511        underneath - otherwise the default `$GIT_DIR/objects`
 512        directory is used.
 513
 514'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 515        Due to the immutable nature of git objects, old objects can be
 516        archived into shared, read-only directories. This variable
 517        specifies a ":" separated (on Windows ";" separated) list
 518        of git object directories which can be used to search for git
 519        objects. New objects will not be written to these directories.
 520
 521'GIT_DIR'::
 522        If the 'GIT_DIR' environment variable is set then it
 523        specifies a path to use instead of the default `.git`
 524        for the base of the repository.
 525
 526'GIT_WORK_TREE'::
 527        Set the path to the working tree.  The value will not be
 528        used in combination with repositories found automatically in
 529        a .git directory (i.e. $GIT_DIR is not set).
 530        This can also be controlled by the '--work-tree' command line
 531        option and the core.worktree configuration variable.
 532
 533'GIT_CEILING_DIRECTORIES'::
 534        This should be a colon-separated list of absolute paths.
 535        If set, it is a list of directories that git should not chdir
 536        up into while looking for a repository directory.
 537        It will not exclude the current working directory or
 538        a GIT_DIR set on the command line or in the environment.
 539        (Useful for excluding slow-loading network directories.)
 540
 541git Commits
 542~~~~~~~~~~~
 543'GIT_AUTHOR_NAME'::
 544'GIT_AUTHOR_EMAIL'::
 545'GIT_AUTHOR_DATE'::
 546'GIT_COMMITTER_NAME'::
 547'GIT_COMMITTER_EMAIL'::
 548'GIT_COMMITTER_DATE'::
 549'EMAIL'::
 550        see linkgit:git-commit-tree[1]
 551
 552git Diffs
 553~~~~~~~~~
 554'GIT_DIFF_OPTS'::
 555        Only valid setting is "--unified=??" or "-u??" to set the
 556        number of context lines shown when a unified diff is created.
 557        This takes precedence over any "-U" or "--unified" option
 558        value passed on the git diff command line.
 559
 560'GIT_EXTERNAL_DIFF'::
 561        When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 562        program named by it is called, instead of the diff invocation
 563        described above.  For a path that is added, removed, or modified,
 564        'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 565
 566        path old-file old-hex old-mode new-file new-hex new-mode
 567+
 568where:
 569
 570        <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 571                         contents of <old|new>,
 572        <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 573        <old|new>-mode:: are the octal representation of the file modes.
 574
 575+
 576The file parameters can point at the user's working file
 577(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 578when a new file is added), or a temporary file (e.g. `old-file` in the
 579index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 580temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 581+
 582For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 583parameter, <path>.
 584
 585other
 586~~~~~
 587'GIT_MERGE_VERBOSITY'::
 588        A number controlling the amount of output shown by
 589        the recursive merge strategy.  Overrides merge.verbosity.
 590        See linkgit:git-merge[1]
 591
 592'GIT_PAGER'::
 593        This environment variable overrides `$PAGER`. If it is set
 594        to an empty string or to the value "cat", git will not launch
 595        a pager.  See also the `core.pager` option in
 596        linkgit:git-config[1].
 597
 598'GIT_SSH'::
 599        If this environment variable is set then 'git fetch'
 600        and 'git push' will use this command instead
 601        of 'ssh' when they need to connect to a remote system.
 602        The '$GIT_SSH' command will be given exactly two arguments:
 603        the 'username@host' (or just 'host') from the URL and the
 604        shell command to execute on that remote system.
 605+
 606To pass options to the program that you want to list in GIT_SSH
 607you will need to wrap the program and options into a shell script,
 608then set GIT_SSH to refer to the shell script.
 609+
 610Usually it is easier to configure any desired options through your
 611personal `.ssh/config` file.  Please consult your ssh documentation
 612for further details.
 613
 614'GIT_FLUSH'::
 615        If this environment variable is set to "1", then commands such
 616        as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 617        and 'git whatchanged' will force a flush of the output stream
 618        after each commit-oriented record have been flushed.   If this
 619        variable is set to "0", the output of these commands will be done
 620        using completely buffered I/O.   If this environment variable is
 621        not set, git will choose buffered or record-oriented flushing
 622        based on whether stdout appears to be redirected to a file or not.
 623
 624'GIT_TRACE'::
 625        If this variable is set to "1", "2" or "true" (comparison
 626        is case insensitive), git will print `trace:` messages on
 627        stderr telling about alias expansion, built-in command
 628        execution and external command execution.
 629        If this variable is set to an integer value greater than 1
 630        and lower than 10 (strictly) then git will interpret this
 631        value as an open file descriptor and will try to write the
 632        trace messages into this file descriptor.
 633        Alternatively, if this variable is set to an absolute path
 634        (starting with a '/' character), git will interpret this
 635        as a file path and will try to write the trace messages
 636        into it.
 637
 638Discussion[[Discussion]]
 639------------------------
 640
 641More detail on the following is available from the
 642link:user-manual.html#git-concepts[git concepts chapter of the
 643user-manual] and linkgit:gitcore-tutorial[7].
 644
 645A git project normally consists of a working directory with a ".git"
 646subdirectory at the top level.  The .git directory contains, among other
 647things, a compressed object database representing the complete history
 648of the project, an "index" file which links that history to the current
 649contents of the working tree, and named pointers into that history such
 650as tags and branch heads.
 651
 652The object database contains objects of three main types: blobs, which
 653hold file data; trees, which point to blobs and other trees to build up
 654directory hierarchies; and commits, which each reference a single tree
 655and some number of parent commits.
 656
 657The commit, equivalent to what other systems call a "changeset" or
 658"version", represents a step in the project's history, and each parent
 659represents an immediately preceding step.  Commits with more than one
 660parent represent merges of independent lines of development.
 661
 662All objects are named by the SHA1 hash of their contents, normally
 663written as a string of 40 hex digits.  Such names are globally unique.
 664The entire history leading up to a commit can be vouched for by signing
 665just that commit.  A fourth object type, the tag, is provided for this
 666purpose.
 667
 668When first created, objects are stored in individual files, but for
 669efficiency may later be compressed together into "pack files".
 670
 671Named pointers called refs mark interesting points in history.  A ref
 672may contain the SHA1 name of an object or the name of another ref.  Refs
 673with names beginning `ref/head/` contain the SHA1 name of the most
 674recent commit (or "head") of a branch under development.  SHA1 names of
 675tags of interest are stored under `ref/tags/`.  A special ref named
 676`HEAD` contains the name of the currently checked-out branch.
 677
 678The index file is initialized with a list of all paths and, for each
 679path, a blob object and a set of attributes.  The blob object represents
 680the contents of the file as of the head of the current branch.  The
 681attributes (last modified time, size, etc.) are taken from the
 682corresponding file in the working tree.  Subsequent changes to the
 683working tree can be found by comparing these attributes.  The index may
 684be updated with new content, and new commits may be created from the
 685content stored in the index.
 686
 687The index is also capable of storing multiple entries (called "stages")
 688for a given pathname.  These stages are used to hold the various
 689unmerged version of a file when a merge is in progress.
 690
 691Authors
 692-------
 693* git's founding father is Linus Torvalds <torvalds@osdl.org>.
 694* The current git nurse is Junio C Hamano <gitster@pobox.com>.
 695* The git potty was written by Andreas Ericsson <ae@op5.se>.
 696* General upbringing is handled by the git-list <git@vger.kernel.org>.
 697
 698Documentation
 699--------------
 700The documentation for git suite was started by David Greaves
 701<david@dgreaves.com>, and later enhanced greatly by the
 702contributors on the git-list <git@vger.kernel.org>.
 703
 704SEE ALSO
 705--------
 706linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 707link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 708linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 709linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 710linkgit:gitworkflows[7]
 711
 712GIT
 713---
 714Part of the linkgit:git[1] suite