Documentation/git.txt

   1 git(1)
   2 ======
   3
   4 NAME
   5 ----
   6 git - the stupid content tracker
   7
   8
   9 SYNOPSIS
  10 --------
  11 [verse]
  12 'git' [--version] [--exec-path[=<path>]] [--html-path]
  13     [-p|--paginate|--no-pager] [--no-replace-objects]
  14     [--bare] [--git-dir=<path>] [--work-tree=<path>]
  15     [-c <name>=<value>]
  16     [--help] <command> [<args>]
  17
  18 DESCRIPTION
  19 -----------
  20 Git is a fast, scalable, distributed revision control system with an
  21 unusually rich command set that provides both high-level operations
  22 and full access to internals.
  23
  24 See linkgit:gittutorial[7] to get started, then see
  25 link:everyday.html[Everyday Git] for a useful minimum set of commands, and
  26 "man git-commandname" for documentation of each command.  CVS users may
  27 also want to read linkgit:gitcvs-migration[7].  See
  28 the link:user-manual.html[Git User's Manual] for a more in-depth
  29 introduction.
  30
  31 The '<command>' is either a name of a Git command (see below) or an alias
  32 as defined in the configuration file (see linkgit:git-config[1]).
  33
  34 Formatted and hyperlinked version of the latest git
  35 documentation can be viewed at
  36 `http://www.kernel.org/pub/software/scm/git/docs/`.
  37
  38 ifdef::stalenotes[]
  39 [NOTE]
  40 ============
  41
  42 You are reading the documentation for the latest (possibly
  43 unreleased) version of git, that is available from 'master'
  44 branch of the `git.git` repository.
  45 Documentation for older releases are available here:
  46
  47 * link:v1.7.3.5/git.html[documentation for release 1.7.3.5]
  48
  49 * release notes for
  50   link:RelNotes/1.7.3.5.txt[1.7.3.5],
  51   link:RelNotes/1.7.3.4.txt[1.7.3.4],
  52   link:RelNotes/1.7.3.3.txt[1.7.3.3],
  53   link:RelNotes/1.7.3.2.txt[1.7.3.2],
  54   link:RelNotes/1.7.3.1.txt[1.7.3.1],
  55   link:RelNotes/1.7.3.txt[1.7.3].
  56
  57 * link:v1.7.2.5/git.html[documentation for release 1.7.2.5]
  58
  59 * release notes for
  60   link:RelNotes/1.7.2.5.txt[1.7.2.5],
  61   link:RelNotes/1.7.2.4.txt[1.7.2.4],
  62   link:RelNotes/1.7.2.3.txt[1.7.2.3],
  63   link:RelNotes/1.7.2.2.txt[1.7.2.2],
  64   link:RelNotes/1.7.2.1.txt[1.7.2.1],
  65   link:RelNotes/1.7.2.txt[1.7.2].
  66
  67 * link:v1.7.1.4/git.html[documentation for release 1.7.1.4]
  68
  69 * release notes for
  70   link:RelNotes/1.7.1.4.txt[1.7.1.4],
  71   link:RelNotes/1.7.1.3.txt[1.7.1.3],
  72   link:RelNotes/1.7.1.2.txt[1.7.1.2],
  73   link:RelNotes/1.7.1.1.txt[1.7.1.1],
  74   link:RelNotes/1.7.1.txt[1.7.1].
  75
  76 * link:v1.7.0.9/git.html[documentation for release 1.7.0.9]
  77
  78 * release notes for
  79   link:RelNotes/1.7.0.9.txt[1.7.0.9],
  80   link:RelNotes/1.7.0.8.txt[1.7.0.8],
  81   link:RelNotes/1.7.0.7.txt[1.7.0.7],
  82   link:RelNotes/1.7.0.6.txt[1.7.0.6],
  83   link:RelNotes/1.7.0.5.txt[1.7.0.5],
  84   link:RelNotes/1.7.0.4.txt[1.7.0.4],
  85   link:RelNotes/1.7.0.3.txt[1.7.0.3],
  86   link:RelNotes/1.7.0.2.txt[1.7.0.2],
  87   link:RelNotes/1.7.0.1.txt[1.7.0.1],
  88   link:RelNotes/1.7.0.txt[1.7.0].
  89
  90 * link:v1.6.6.3/git.html[documentation for release 1.6.6.3]
  91
  92 * release notes for
  93   link:RelNotes/1.6.6.3.txt[1.6.6.3],
  94   link:RelNotes/1.6.6.2.txt[1.6.6.2],
  95   link:RelNotes/1.6.6.1.txt[1.6.6.1],
  96   link:RelNotes/1.6.6.txt[1.6.6].
  97
  98 * link:v1.6.5.9/git.html[documentation for release 1.6.5.9]
  99
 100 * release notes for
 101   link:RelNotes/1.6.5.9.txt[1.6.5.9],
 102   link:RelNotes/1.6.5.8.txt[1.6.5.8],
 103   link:RelNotes/1.6.5.7.txt[1.6.5.7],
 104   link:RelNotes/1.6.5.6.txt[1.6.5.6],
 105   link:RelNotes/1.6.5.5.txt[1.6.5.5],
 106   link:RelNotes/1.6.5.4.txt[1.6.5.4],
 107   link:RelNotes/1.6.5.3.txt[1.6.5.3],
 108   link:RelNotes/1.6.5.2.txt[1.6.5.2],
 109   link:RelNotes/1.6.5.1.txt[1.6.5.1],
 110   link:RelNotes/1.6.5.txt[1.6.5].
 111
 112 * link:v1.6.4.5/git.html[documentation for release 1.6.4.5]
 113
 114 * release notes for
 115   link:RelNotes/1.6.4.5.txt[1.6.4.5],
 116   link:RelNotes/1.6.4.4.txt[1.6.4.4],
 117   link:RelNotes/1.6.4.3.txt[1.6.4.3],
 118   link:RelNotes/1.6.4.2.txt[1.6.4.2],
 119   link:RelNotes/1.6.4.1.txt[1.6.4.1],
 120   link:RelNotes/1.6.4.txt[1.6.4].
 121
 122 * link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
 123
 124 * release notes for
 125   link:RelNotes/1.6.3.4.txt[1.6.3.4],
 126   link:RelNotes/1.6.3.3.txt[1.6.3.3],
 127   link:RelNotes/1.6.3.2.txt[1.6.3.2],
 128   link:RelNotes/1.6.3.1.txt[1.6.3.1],
 129   link:RelNotes/1.6.3.txt[1.6.3].
 130
 131 * release notes for
 132   link:RelNotes/1.6.2.5.txt[1.6.2.5],
 133   link:RelNotes/1.6.2.4.txt[1.6.2.4],
 134   link:RelNotes/1.6.2.3.txt[1.6.2.3],
 135   link:RelNotes/1.6.2.2.txt[1.6.2.2],
 136   link:RelNotes/1.6.2.1.txt[1.6.2.1],
 137   link:RelNotes/1.6.2.txt[1.6.2].
 138
 139 * link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
 140
 141 * release notes for
 142   link:RelNotes/1.6.1.3.txt[1.6.1.3],
 143   link:RelNotes/1.6.1.2.txt[1.6.1.2],
 144   link:RelNotes/1.6.1.1.txt[1.6.1.1],
 145   link:RelNotes/1.6.1.txt[1.6.1].
 146
 147 * link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 148
 149 * release notes for
 150   link:RelNotes/1.6.0.6.txt[1.6.0.6],
 151   link:RelNotes/1.6.0.5.txt[1.6.0.5],
 152   link:RelNotes/1.6.0.4.txt[1.6.0.4],
 153   link:RelNotes/1.6.0.3.txt[1.6.0.3],
 154   link:RelNotes/1.6.0.2.txt[1.6.0.2],
 155   link:RelNotes/1.6.0.1.txt[1.6.0.1],
 156   link:RelNotes/1.6.0.txt[1.6.0].
 157
 158 * link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 159
 160 * release notes for
 161   link:RelNotes/1.5.6.6.txt[1.5.6.6],
 162   link:RelNotes/1.5.6.5.txt[1.5.6.5],
 163   link:RelNotes/1.5.6.4.txt[1.5.6.4],
 164   link:RelNotes/1.5.6.3.txt[1.5.6.3],
 165   link:RelNotes/1.5.6.2.txt[1.5.6.2],
 166   link:RelNotes/1.5.6.1.txt[1.5.6.1],
 167   link:RelNotes/1.5.6.txt[1.5.6].
 168
 169 * link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 170
 171 * release notes for
 172   link:RelNotes/1.5.5.6.txt[1.5.5.6],
 173   link:RelNotes/1.5.5.5.txt[1.5.5.5],
 174   link:RelNotes/1.5.5.4.txt[1.5.5.4],
 175   link:RelNotes/1.5.5.3.txt[1.5.5.3],
 176   link:RelNotes/1.5.5.2.txt[1.5.5.2],
 177   link:RelNotes/1.5.5.1.txt[1.5.5.1],
 178   link:RelNotes/1.5.5.txt[1.5.5].
 179
 180 * link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 181
 182 * release notes for
 183   link:RelNotes/1.5.4.7.txt[1.5.4.7],
 184   link:RelNotes/1.5.4.6.txt[1.5.4.6],
 185   link:RelNotes/1.5.4.5.txt[1.5.4.5],
 186   link:RelNotes/1.5.4.4.txt[1.5.4.4],
 187   link:RelNotes/1.5.4.3.txt[1.5.4.3],
 188   link:RelNotes/1.5.4.2.txt[1.5.4.2],
 189   link:RelNotes/1.5.4.1.txt[1.5.4.1],
 190   link:RelNotes/1.5.4.txt[1.5.4].
 191
 192 * link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 193
 194 * release notes for
 195   link:RelNotes/1.5.3.8.txt[1.5.3.8],
 196   link:RelNotes/1.5.3.7.txt[1.5.3.7],
 197   link:RelNotes/1.5.3.6.txt[1.5.3.6],
 198   link:RelNotes/1.5.3.5.txt[1.5.3.5],
 199   link:RelNotes/1.5.3.4.txt[1.5.3.4],
 200   link:RelNotes/1.5.3.3.txt[1.5.3.3],
 201   link:RelNotes/1.5.3.2.txt[1.5.3.2],
 202   link:RelNotes/1.5.3.1.txt[1.5.3.1],
 203   link:RelNotes/1.5.3.txt[1.5.3].
 204
 205 * link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 206
 207 * release notes for
 208   link:RelNotes/1.5.2.5.txt[1.5.2.5],
 209   link:RelNotes/1.5.2.4.txt[1.5.2.4],
 210   link:RelNotes/1.5.2.3.txt[1.5.2.3],
 211   link:RelNotes/1.5.2.2.txt[1.5.2.2],
 212   link:RelNotes/1.5.2.1.txt[1.5.2.1],
 213   link:RelNotes/1.5.2.txt[1.5.2].
 214
 215 * link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 216
 217 * release notes for
 218   link:RelNotes/1.5.1.6.txt[1.5.1.6],
 219   link:RelNotes/1.5.1.5.txt[1.5.1.5],
 220   link:RelNotes/1.5.1.4.txt[1.5.1.4],
 221   link:RelNotes/1.5.1.3.txt[1.5.1.3],
 222   link:RelNotes/1.5.1.2.txt[1.5.1.2],
 223   link:RelNotes/1.5.1.1.txt[1.5.1.1],
 224   link:RelNotes/1.5.1.txt[1.5.1].
 225
 226 * link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 227
 228 * release notes for
 229   link:RelNotes/1.5.0.7.txt[1.5.0.7],
 230   link:RelNotes/1.5.0.6.txt[1.5.0.6],
 231   link:RelNotes/1.5.0.5.txt[1.5.0.5],
 232   link:RelNotes/1.5.0.3.txt[1.5.0.3],
 233   link:RelNotes/1.5.0.2.txt[1.5.0.2],
 234   link:RelNotes/1.5.0.1.txt[1.5.0.1],
 235   link:RelNotes/1.5.0.txt[1.5.0].
 236
 237 * documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 238   link:v1.3.3/git.html[1.3.3],
 239   link:v1.2.6/git.html[1.2.6],
 240   link:v1.0.13/git.html[1.0.13].
 241
 242 ============
 243
 244 endif::stalenotes[]
 245
 246 OPTIONS
 247 -------
 248 --version::
 249         Prints the git suite version that the 'git' program came from.
 250
 251 --help::
 252         Prints the synopsis and a list of the most commonly used
 253         commands. If the option '--all' or '-a' is given then all
 254         available commands are printed. If a git command is named this
 255         option will bring up the manual page for that command.
 256 +
 257 Other options are available to control how the manual page is
 258 displayed. See linkgit:git-help[1] for more information,
 259 because `git --help ...` is converted internally into `git
 260 help ...`.
 261
 262 -c <name>=<value>::
 263         Pass a configuration parameter to the command. The value
 264         given will override values from configuration files.
 265         The <name> is expected in the same format as listed by
 266         'git config' (subkeys separated by dots).
 267
 268 --exec-path[=<path>]::
 269         Path to wherever your core git programs are installed.
 270         This can also be controlled by setting the GIT_EXEC_PATH
 271         environment variable. If no path is given, 'git' will print
 272         the current setting and then exit.
 273
 274 --html-path::
 275         Print the path to wherever your git HTML documentation is installed
 276         and exit.
 277
 278 -p::
 279 --paginate::
 280         Pipe all output into 'less' (or if set, $PAGER) if standard
 281         output is a terminal.  This overrides the `pager.<cmd>`
 282         configuration options (see the "Configuration Mechanism" section
 283         below).
 284
 285 --no-pager::
 286         Do not pipe git output into a pager.
 287
 288 --git-dir=<path>::
 289         Set the path to the repository. This can also be controlled by
 290         setting the GIT_DIR environment variable. It can be an absolute
 291         path or relative path to current working directory.
 292
 293 --work-tree=<path>::
 294         Set the path to the working tree. It can be an absolute path
 295         or a path relative to the current working directory.
 296         This can also be controlled by setting the GIT_WORK_TREE
 297         environment variable and the core.worktree configuration
 298         variable (see core.worktree in linkgit:git-config[1] for a
 299         more detailed discussion).
 300
 301 --bare::
 302         Treat the repository as a bare repository.  If GIT_DIR
 303         environment is not set, it is set to the current working
 304         directory.
 305
 306 --no-replace-objects::
 307         Do not use replacement refs to replace git objects. See
 308         linkgit:git-replace[1] for more information.
 309
 310
 311 FURTHER DOCUMENTATION
 312 ---------------------
 313
 314 See the references above to get started using git.  The following is
 315 probably more detail than necessary for a first-time user.
 316
 317 The link:user-manual.html#git-concepts[git concepts chapter of the
 318 user-manual] and linkgit:gitcore-tutorial[7] both provide
 319 introductions to the underlying git architecture.
 320
 321 See linkgit:gitworkflows[7] for an overview of recommended workflows.
 322
 323 See also the link:howto-index.html[howto] documents for some useful
 324 examples.
 325
 326 The internals are documented in the
 327 link:technical/api-index.html[GIT API documentation].
 328
 329 GIT COMMANDS
 330 ------------
 331
 332 We divide git into high level ("porcelain") commands and low level
 333 ("plumbing") commands.
 334
 335 High-level commands (porcelain)
 336 -------------------------------
 337
 338 We separate the porcelain commands into the main commands and some
 339 ancillary user utilities.
 340
 341 Main porcelain commands
 342 ~~~~~~~~~~~~~~~~~~~~~~~
 343
 344 include::cmds-mainporcelain.txt[]
 345
 346 Ancillary Commands
 347 ~~~~~~~~~~~~~~~~~~
 348 Manipulators:
 349
 350 include::cmds-ancillarymanipulators.txt[]
 351
 352 Interrogators:
 353
 354 include::cmds-ancillaryinterrogators.txt[]
 355
 356
 357 Interacting with Others
 358 ~~~~~~~~~~~~~~~~~~~~~~~
 359
 360 These commands are to interact with foreign SCM and with other
 361 people via patch over e-mail.
 362
 363 include::cmds-foreignscminterface.txt[]
 364
 365
 366 Low-level commands (plumbing)
 367 -----------------------------
 368
 369 Although git includes its
 370 own porcelain layer, its low-level commands are sufficient to support
 371 development of alternative porcelains.  Developers of such porcelains
 372 might start by reading about linkgit:git-update-index[1] and
 373 linkgit:git-read-tree[1].
 374
 375 The interface (input, output, set of options and the semantics)
 376 to these low-level commands are meant to be a lot more stable
 377 than Porcelain level commands, because these commands are
 378 primarily for scripted use.  The interface to Porcelain commands
 379 on the other hand are subject to change in order to improve the
 380 end user experience.
 381
 382 The following description divides
 383 the low-level commands into commands that manipulate objects (in
 384 the repository, index, and working tree), commands that interrogate and
 385 compare objects, and commands that move objects and references between
 386 repositories.
 387
 388
 389 Manipulation commands
 390 ~~~~~~~~~~~~~~~~~~~~~
 391
 392 include::cmds-plumbingmanipulators.txt[]
 393
 394
 395 Interrogation commands
 396 ~~~~~~~~~~~~~~~~~~~~~~
 397
 398 include::cmds-plumbinginterrogators.txt[]
 399
 400 In general, the interrogate commands do not touch the files in
 401 the working tree.
 402
 403
 404 Synching repositories
 405 ~~~~~~~~~~~~~~~~~~~~~
 406
 407 include::cmds-synchingrepositories.txt[]
 408
 409 The following are helper commands used by the above; end users
 410 typically do not use them directly.
 411
 412 include::cmds-synchelpers.txt[]
 413
 414
 415 Internal helper commands
 416 ~~~~~~~~~~~~~~~~~~~~~~~~
 417
 418 These are internal helper commands used by other commands; end
 419 users typically do not use them directly.
 420
 421 include::cmds-purehelpers.txt[]
 422
 423
 424 Configuration Mechanism
 425 -----------------------
 426
 427 Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 428 is used to hold per-repository configuration options.  It is a
 429 simple text file modeled after `.ini` format familiar to some
 430 people.  Here is an example:
 431
 432 ------------
 433 #
 434 # A '#' or ';' character indicates a comment.
 435 #
 436
 437 ; core variables
 438 [core]
 439         ; Don't trust file modes
 440         filemode = false
 441
 442 ; user identity
 443 [user]
 444         name = "Junio C Hamano"
 445         email = "junkio@twinsun.com"
 446
 447 ------------
 448
 449 Various commands read from the configuration file and adjust
 450 their operation accordingly.  See linkgit:git-config[1] for a
 451 list.
 452
 453
 454 Identifier Terminology
 455 ----------------------
 456 <object>::
 457         Indicates the object name for any type of object.
 458
 459 <blob>::
 460         Indicates a blob object name.
 461
 462 <tree>::
 463         Indicates a tree object name.
 464
 465 <commit>::
 466         Indicates a commit object name.
 467
 468 <tree-ish>::
 469         Indicates a tree, commit or tag object name.  A
 470         command that takes a <tree-ish> argument ultimately wants to
 471         operate on a <tree> object but automatically dereferences
 472         <commit> and <tag> objects that point at a <tree>.
 473
 474 <commit-ish>::
 475         Indicates a commit or tag object name.  A
 476         command that takes a <commit-ish> argument ultimately wants to
 477         operate on a <commit> object but automatically dereferences
 478         <tag> objects that point at a <commit>.
 479
 480 <type>::
 481         Indicates that an object type is required.
 482         Currently one of: `blob`, `tree`, `commit`, or `tag`.
 483
 484 <file>::
 485         Indicates a filename - almost always relative to the
 486         root of the tree structure `GIT_INDEX_FILE` describes.
 487
 488 Symbolic Identifiers
 489 --------------------
 490 Any git command accepting any <object> can also use the following
 491 symbolic notation:
 492
 493 HEAD::
 494         indicates the head of the current branch (i.e. the
 495         contents of `$GIT_DIR/HEAD`).
 496
 497 <tag>::
 498         a valid tag 'name'
 499         (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 500
 501 <head>::
 502         a valid head 'name'
 503         (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 504
 505 For a more complete list of ways to spell object names, see
 506 "SPECIFYING REVISIONS" section in linkgit:gitrevisions[7].
 507
 508
 509 File/Directory Structure
 510 ------------------------
 511
 512 Please see the linkgit:gitrepository-layout[5] document.
 513
 514 Read linkgit:githooks[5] for more details about each hook.
 515
 516 Higher level SCMs may provide and manage additional information in the
 517 `$GIT_DIR`.
 518
 519
 520 Terminology
 521 -----------
 522 Please see linkgit:gitglossary[7].
 523
 524
 525 Environment Variables
 526 ---------------------
 527 Various git commands use the following environment variables:
 528
 529 The git Repository
 530 ~~~~~~~~~~~~~~~~~~
 531 These environment variables apply to 'all' core git commands. Nb: it
 532 is worth noting that they may be used/overridden by SCMS sitting above
 533 git so take care if using Cogito etc.
 534
 535 'GIT_INDEX_FILE'::
 536         This environment allows the specification of an alternate
 537         index file. If not specified, the default of `$GIT_DIR/index`
 538         is used.
 539
 540 'GIT_OBJECT_DIRECTORY'::
 541         If the object storage directory is specified via this
 542         environment variable then the sha1 directories are created
 543         underneath - otherwise the default `$GIT_DIR/objects`
 544         directory is used.
 545
 546 'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 547         Due to the immutable nature of git objects, old objects can be
 548         archived into shared, read-only directories. This variable
 549         specifies a ":" separated (on Windows ";" separated) list
 550         of git object directories which can be used to search for git
 551         objects. New objects will not be written to these directories.
 552
 553 'GIT_DIR'::
 554         If the 'GIT_DIR' environment variable is set then it
 555         specifies a path to use instead of the default `.git`
 556         for the base of the repository.
 557
 558 'GIT_WORK_TREE'::
 559         Set the path to the working tree.  The value will not be
 560         used in combination with repositories found automatically in
 561         a .git directory (i.e. $GIT_DIR is not set).
 562         This can also be controlled by the '--work-tree' command line
 563         option and the core.worktree configuration variable.
 564
 565 'GIT_CEILING_DIRECTORIES'::
 566         This should be a colon-separated list of absolute paths.
 567         If set, it is a list of directories that git should not chdir
 568         up into while looking for a repository directory.
 569         It will not exclude the current working directory or
 570         a GIT_DIR set on the command line or in the environment.
 571         (Useful for excluding slow-loading network directories.)
 572
 573 'GIT_DISCOVERY_ACROSS_FILESYSTEM'::
 574         When run in a directory that does not have ".git" repository
 575         directory, git tries to find such a directory in the parent
 576         directories to find the top of the working tree, but by default it
 577         does not cross filesystem boundaries.  This environment variable
 578         can be set to true to tell git not to stop at filesystem
 579         boundaries.  Like 'GIT_CEILING_DIRECTORIES', this will not affect
 580         an explicit repository directory set via 'GIT_DIR' or on the
 581         command line.
 582
 583 git Commits
 584 ~~~~~~~~~~~
 585 'GIT_AUTHOR_NAME'::
 586 'GIT_AUTHOR_EMAIL'::
 587 'GIT_AUTHOR_DATE'::
 588 'GIT_COMMITTER_NAME'::
 589 'GIT_COMMITTER_EMAIL'::
 590 'GIT_COMMITTER_DATE'::
 591 'EMAIL'::
 592         see linkgit:git-commit-tree[1]
 593
 594 git Diffs
 595 ~~~~~~~~~
 596 'GIT_DIFF_OPTS'::
 597         Only valid setting is "--unified=??" or "-u??" to set the
 598         number of context lines shown when a unified diff is created.
 599         This takes precedence over any "-U" or "--unified" option
 600         value passed on the git diff command line.
 601
 602 'GIT_EXTERNAL_DIFF'::
 603         When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 604         program named by it is called, instead of the diff invocation
 605         described above.  For a path that is added, removed, or modified,
 606         'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 607
 608         path old-file old-hex old-mode new-file new-hex new-mode
 609 +
 610 where:
 611
 612         <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 613                          contents of <old|new>,
 614         <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 615         <old|new>-mode:: are the octal representation of the file modes.
 616
 617 +
 618 The file parameters can point at the user's working file
 619 (e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 620 when a new file is added), or a temporary file (e.g. `old-file` in the
 621 index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 622 temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 623 +
 624 For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 625 parameter, <path>.
 626
 627 other
 628 ~~~~~
 629 'GIT_MERGE_VERBOSITY'::
 630         A number controlling the amount of output shown by
 631         the recursive merge strategy.  Overrides merge.verbosity.
 632         See linkgit:git-merge[1]
 633
 634 'GIT_PAGER'::
 635         This environment variable overrides `$PAGER`. If it is set
 636         to an empty string or to the value "cat", git will not launch
 637         a pager.  See also the `core.pager` option in
 638         linkgit:git-config[1].
 639
 640 'GIT_SSH'::
 641         If this environment variable is set then 'git fetch'
 642         and 'git push' will use this command instead
 643         of 'ssh' when they need to connect to a remote system.
 644         The '$GIT_SSH' command will be given exactly two arguments:
 645         the 'username@host' (or just 'host') from the URL and the
 646         shell command to execute on that remote system.
 647 +
 648 To pass options to the program that you want to list in GIT_SSH
 649 you will need to wrap the program and options into a shell script,
 650 then set GIT_SSH to refer to the shell script.
 651 +
 652 Usually it is easier to configure any desired options through your
 653 personal `.ssh/config` file.  Please consult your ssh documentation
 654 for further details.
 655
 656 'GIT_ASKPASS'::
 657         If this environment variable is set, then git commands which need to
 658         acquire passwords or passphrases (e.g. for HTTP or IMAP authentication)
 659         will call this program with a suitable prompt as command line argument
 660         and read the password from its STDOUT. See also the 'core.askpass'
 661         option in linkgit:git-config[1].
 662
 663 'GIT_FLUSH'::
 664         If this environment variable is set to "1", then commands such
 665         as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 666         and 'git whatchanged' will force a flush of the output stream
 667         after each commit-oriented record have been flushed.   If this
 668         variable is set to "0", the output of these commands will be done
 669         using completely buffered I/O.   If this environment variable is
 670         not set, git will choose buffered or record-oriented flushing
 671         based on whether stdout appears to be redirected to a file or not.
 672
 673 'GIT_TRACE'::
 674         If this variable is set to "1", "2" or "true" (comparison
 675         is case insensitive), git will print `trace:` messages on
 676         stderr telling about alias expansion, built-in command
 677         execution and external command execution.
 678         If this variable is set to an integer value greater than 1
 679         and lower than 10 (strictly) then git will interpret this
 680         value as an open file descriptor and will try to write the
 681         trace messages into this file descriptor.
 682         Alternatively, if this variable is set to an absolute path
 683         (starting with a '/' character), git will interpret this
 684         as a file path and will try to write the trace messages
 685         into it.
 686
 687 Discussion[[Discussion]]
 688 ------------------------
 689
 690 More detail on the following is available from the
 691 link:user-manual.html#git-concepts[git concepts chapter of the
 692 user-manual] and linkgit:gitcore-tutorial[7].
 693
 694 A git project normally consists of a working directory with a ".git"
 695 subdirectory at the top level.  The .git directory contains, among other
 696 things, a compressed object database representing the complete history
 697 of the project, an "index" file which links that history to the current
 698 contents of the working tree, and named pointers into that history such
 699 as tags and branch heads.
 700
 701 The object database contains objects of three main types: blobs, which
 702 hold file data; trees, which point to blobs and other trees to build up
 703 directory hierarchies; and commits, which each reference a single tree
 704 and some number of parent commits.
 705
 706 The commit, equivalent to what other systems call a "changeset" or
 707 "version", represents a step in the project's history, and each parent
 708 represents an immediately preceding step.  Commits with more than one
 709 parent represent merges of independent lines of development.
 710
 711 All objects are named by the SHA1 hash of their contents, normally
 712 written as a string of 40 hex digits.  Such names are globally unique.
 713 The entire history leading up to a commit can be vouched for by signing
 714 just that commit.  A fourth object type, the tag, is provided for this
 715 purpose.
 716
 717 When first created, objects are stored in individual files, but for
 718 efficiency may later be compressed together into "pack files".
 719
 720 Named pointers called refs mark interesting points in history.  A ref
 721 may contain the SHA1 name of an object or the name of another ref.  Refs
 722 with names beginning `ref/head/` contain the SHA1 name of the most
 723 recent commit (or "head") of a branch under development.  SHA1 names of
 724 tags of interest are stored under `ref/tags/`.  A special ref named
 725 `HEAD` contains the name of the currently checked-out branch.
 726
 727 The index file is initialized with a list of all paths and, for each
 728 path, a blob object and a set of attributes.  The blob object represents
 729 the contents of the file as of the head of the current branch.  The
 730 attributes (last modified time, size, etc.) are taken from the
 731 corresponding file in the working tree.  Subsequent changes to the
 732 working tree can be found by comparing these attributes.  The index may
 733 be updated with new content, and new commits may be created from the
 734 content stored in the index.
 735
 736 The index is also capable of storing multiple entries (called "stages")
 737 for a given pathname.  These stages are used to hold the various
 738 unmerged version of a file when a merge is in progress.
 739
 740 Authors
 741 -------
 742 * git's founding father is Linus Torvalds <torvalds@osdl.org>.
 743 * The current git nurse is Junio C Hamano <gitster@pobox.com>.
 744 * The git potty was written by Andreas Ericsson <ae@op5.se>.
 745 * General upbringing is handled by the git-list <git@vger.kernel.org>.
 746
 747 Documentation
 748 --------------
 749 The documentation for git suite was started by David Greaves
 750 <david@dgreaves.com>, and later enhanced greatly by the
 751 contributors on the git-list <git@vger.kernel.org>.
 752
 753 Reporting Bugs
 754 --------------
 755
 756 Report bugs to the Git mailing list <git@vger.kernel.org> where the
 757 development and maintenance is primarily done.  You do not have to be
 758 subscribed to the list to send a message there.
 759
 760 SEE ALSO
 761 --------
 762 linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 763 link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 764 linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 765 linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 766 linkgit:gitworkflows[7]
 767
 768 GIT
 769 ---
 770 Part of the linkgit:git[1] suite