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:v1.7.4.1/git.html[documentation for release 1.7.4.1]
  48
  49 * release notes for
  50   link:RelNotes/1.7.4.1.txt[1.7.4.1],
  51   link:RelNotes/1.7.4.txt[1.7.4].
  52
  53 * link:v1.7.3.5/git.html[documentation for release 1.7.3.5]
  54
  55 * release notes for
  56   link:RelNotes/1.7.3.5.txt[1.7.3.5],
  57   link:RelNotes/1.7.3.4.txt[1.7.3.4],
  58   link:RelNotes/1.7.3.3.txt[1.7.3.3],
  59   link:RelNotes/1.7.3.2.txt[1.7.3.2],
  60   link:RelNotes/1.7.3.1.txt[1.7.3.1],
  61   link:RelNotes/1.7.3.txt[1.7.3].
  62
  63 * link:v1.7.2.5/git.html[documentation for release 1.7.2.5]
  64
  65 * release notes for
  66   link:RelNotes/1.7.2.5.txt[1.7.2.5],
  67   link:RelNotes/1.7.2.4.txt[1.7.2.4],
  68   link:RelNotes/1.7.2.3.txt[1.7.2.3],
  69   link:RelNotes/1.7.2.2.txt[1.7.2.2],
  70   link:RelNotes/1.7.2.1.txt[1.7.2.1],
  71   link:RelNotes/1.7.2.txt[1.7.2].
  72
  73 * link:v1.7.1.4/git.html[documentation for release 1.7.1.4]
  74
  75 * release notes for
  76   link:RelNotes/1.7.1.4.txt[1.7.1.4],
  77   link:RelNotes/1.7.1.3.txt[1.7.1.3],
  78   link:RelNotes/1.7.1.2.txt[1.7.1.2],
  79   link:RelNotes/1.7.1.1.txt[1.7.1.1],
  80   link:RelNotes/1.7.1.txt[1.7.1].
  81
  82 * link:v1.7.0.9/git.html[documentation for release 1.7.0.9]
  83
  84 * release notes for
  85   link:RelNotes/1.7.0.9.txt[1.7.0.9],
  86   link:RelNotes/1.7.0.8.txt[1.7.0.8],
  87   link:RelNotes/1.7.0.7.txt[1.7.0.7],
  88   link:RelNotes/1.7.0.6.txt[1.7.0.6],
  89   link:RelNotes/1.7.0.5.txt[1.7.0.5],
  90   link:RelNotes/1.7.0.4.txt[1.7.0.4],
  91   link:RelNotes/1.7.0.3.txt[1.7.0.3],
  92   link:RelNotes/1.7.0.2.txt[1.7.0.2],
  93   link:RelNotes/1.7.0.1.txt[1.7.0.1],
  94   link:RelNotes/1.7.0.txt[1.7.0].
  95
  96 * link:v1.6.6.3/git.html[documentation for release 1.6.6.3]
  97
  98 * release notes for
  99   link:RelNotes/1.6.6.3.txt[1.6.6.3],
 100   link:RelNotes/1.6.6.2.txt[1.6.6.2],
 101   link:RelNotes/1.6.6.1.txt[1.6.6.1],
 102   link:RelNotes/1.6.6.txt[1.6.6].
 103
 104 * link:v1.6.5.9/git.html[documentation for release 1.6.5.9]
 105
 106 * release notes for
 107   link:RelNotes/1.6.5.9.txt[1.6.5.9],
 108   link:RelNotes/1.6.5.8.txt[1.6.5.8],
 109   link:RelNotes/1.6.5.7.txt[1.6.5.7],
 110   link:RelNotes/1.6.5.6.txt[1.6.5.6],
 111   link:RelNotes/1.6.5.5.txt[1.6.5.5],
 112   link:RelNotes/1.6.5.4.txt[1.6.5.4],
 113   link:RelNotes/1.6.5.3.txt[1.6.5.3],
 114   link:RelNotes/1.6.5.2.txt[1.6.5.2],
 115   link:RelNotes/1.6.5.1.txt[1.6.5.1],
 116   link:RelNotes/1.6.5.txt[1.6.5].
 117
 118 * link:v1.6.4.5/git.html[documentation for release 1.6.4.5]
 119
 120 * release notes for
 121   link:RelNotes/1.6.4.5.txt[1.6.4.5],
 122   link:RelNotes/1.6.4.4.txt[1.6.4.4],
 123   link:RelNotes/1.6.4.3.txt[1.6.4.3],
 124   link:RelNotes/1.6.4.2.txt[1.6.4.2],
 125   link:RelNotes/1.6.4.1.txt[1.6.4.1],
 126   link:RelNotes/1.6.4.txt[1.6.4].
 127
 128 * link:v1.6.3.4/git.html[documentation for release 1.6.3.4]
 129
 130 * release notes for
 131   link:RelNotes/1.6.3.4.txt[1.6.3.4],
 132   link:RelNotes/1.6.3.3.txt[1.6.3.3],
 133   link:RelNotes/1.6.3.2.txt[1.6.3.2],
 134   link:RelNotes/1.6.3.1.txt[1.6.3.1],
 135   link:RelNotes/1.6.3.txt[1.6.3].
 136
 137 * release notes for
 138   link:RelNotes/1.6.2.5.txt[1.6.2.5],
 139   link:RelNotes/1.6.2.4.txt[1.6.2.4],
 140   link:RelNotes/1.6.2.3.txt[1.6.2.3],
 141   link:RelNotes/1.6.2.2.txt[1.6.2.2],
 142   link:RelNotes/1.6.2.1.txt[1.6.2.1],
 143   link:RelNotes/1.6.2.txt[1.6.2].
 144
 145 * link:v1.6.1.3/git.html[documentation for release 1.6.1.3]
 146
 147 * release notes for
 148   link:RelNotes/1.6.1.3.txt[1.6.1.3],
 149   link:RelNotes/1.6.1.2.txt[1.6.1.2],
 150   link:RelNotes/1.6.1.1.txt[1.6.1.1],
 151   link:RelNotes/1.6.1.txt[1.6.1].
 152
 153 * link:v1.6.0.6/git.html[documentation for release 1.6.0.6]
 154
 155 * release notes for
 156   link:RelNotes/1.6.0.6.txt[1.6.0.6],
 157   link:RelNotes/1.6.0.5.txt[1.6.0.5],
 158   link:RelNotes/1.6.0.4.txt[1.6.0.4],
 159   link:RelNotes/1.6.0.3.txt[1.6.0.3],
 160   link:RelNotes/1.6.0.2.txt[1.6.0.2],
 161   link:RelNotes/1.6.0.1.txt[1.6.0.1],
 162   link:RelNotes/1.6.0.txt[1.6.0].
 163
 164 * link:v1.5.6.6/git.html[documentation for release 1.5.6.6]
 165
 166 * release notes for
 167   link:RelNotes/1.5.6.6.txt[1.5.6.6],
 168   link:RelNotes/1.5.6.5.txt[1.5.6.5],
 169   link:RelNotes/1.5.6.4.txt[1.5.6.4],
 170   link:RelNotes/1.5.6.3.txt[1.5.6.3],
 171   link:RelNotes/1.5.6.2.txt[1.5.6.2],
 172   link:RelNotes/1.5.6.1.txt[1.5.6.1],
 173   link:RelNotes/1.5.6.txt[1.5.6].
 174
 175 * link:v1.5.5.6/git.html[documentation for release 1.5.5.6]
 176
 177 * release notes for
 178   link:RelNotes/1.5.5.6.txt[1.5.5.6],
 179   link:RelNotes/1.5.5.5.txt[1.5.5.5],
 180   link:RelNotes/1.5.5.4.txt[1.5.5.4],
 181   link:RelNotes/1.5.5.3.txt[1.5.5.3],
 182   link:RelNotes/1.5.5.2.txt[1.5.5.2],
 183   link:RelNotes/1.5.5.1.txt[1.5.5.1],
 184   link:RelNotes/1.5.5.txt[1.5.5].
 185
 186 * link:v1.5.4.7/git.html[documentation for release 1.5.4.7]
 187
 188 * release notes for
 189   link:RelNotes/1.5.4.7.txt[1.5.4.7],
 190   link:RelNotes/1.5.4.6.txt[1.5.4.6],
 191   link:RelNotes/1.5.4.5.txt[1.5.4.5],
 192   link:RelNotes/1.5.4.4.txt[1.5.4.4],
 193   link:RelNotes/1.5.4.3.txt[1.5.4.3],
 194   link:RelNotes/1.5.4.2.txt[1.5.4.2],
 195   link:RelNotes/1.5.4.1.txt[1.5.4.1],
 196   link:RelNotes/1.5.4.txt[1.5.4].
 197
 198 * link:v1.5.3.8/git.html[documentation for release 1.5.3.8]
 199
 200 * release notes for
 201   link:RelNotes/1.5.3.8.txt[1.5.3.8],
 202   link:RelNotes/1.5.3.7.txt[1.5.3.7],
 203   link:RelNotes/1.5.3.6.txt[1.5.3.6],
 204   link:RelNotes/1.5.3.5.txt[1.5.3.5],
 205   link:RelNotes/1.5.3.4.txt[1.5.3.4],
 206   link:RelNotes/1.5.3.3.txt[1.5.3.3],
 207   link:RelNotes/1.5.3.2.txt[1.5.3.2],
 208   link:RelNotes/1.5.3.1.txt[1.5.3.1],
 209   link:RelNotes/1.5.3.txt[1.5.3].
 210
 211 * link:v1.5.2.5/git.html[documentation for release 1.5.2.5]
 212
 213 * release notes for
 214   link:RelNotes/1.5.2.5.txt[1.5.2.5],
 215   link:RelNotes/1.5.2.4.txt[1.5.2.4],
 216   link:RelNotes/1.5.2.3.txt[1.5.2.3],
 217   link:RelNotes/1.5.2.2.txt[1.5.2.2],
 218   link:RelNotes/1.5.2.1.txt[1.5.2.1],
 219   link:RelNotes/1.5.2.txt[1.5.2].
 220
 221 * link:v1.5.1.6/git.html[documentation for release 1.5.1.6]
 222
 223 * release notes for
 224   link:RelNotes/1.5.1.6.txt[1.5.1.6],
 225   link:RelNotes/1.5.1.5.txt[1.5.1.5],
 226   link:RelNotes/1.5.1.4.txt[1.5.1.4],
 227   link:RelNotes/1.5.1.3.txt[1.5.1.3],
 228   link:RelNotes/1.5.1.2.txt[1.5.1.2],
 229   link:RelNotes/1.5.1.1.txt[1.5.1.1],
 230   link:RelNotes/1.5.1.txt[1.5.1].
 231
 232 * link:v1.5.0.7/git.html[documentation for release 1.5.0.7]
 233
 234 * release notes for
 235   link:RelNotes/1.5.0.7.txt[1.5.0.7],
 236   link:RelNotes/1.5.0.6.txt[1.5.0.6],
 237   link:RelNotes/1.5.0.5.txt[1.5.0.5],
 238   link:RelNotes/1.5.0.3.txt[1.5.0.3],
 239   link:RelNotes/1.5.0.2.txt[1.5.0.2],
 240   link:RelNotes/1.5.0.1.txt[1.5.0.1],
 241   link:RelNotes/1.5.0.txt[1.5.0].
 242
 243 * documentation for release link:v1.4.4.4/git.html[1.4.4.4],
 244   link:v1.3.3/git.html[1.3.3],
 245   link:v1.2.6/git.html[1.2.6],
 246   link:v1.0.13/git.html[1.0.13].
 247
 248 ============
 249
 250 endif::stalenotes[]
 251
 252 OPTIONS
 253 -------
 254 --version::
 255         Prints the git suite version that the 'git' program came from.
 256
 257 --help::
 258         Prints the synopsis and a list of the most commonly used
 259         commands. If the option '--all' or '-a' is given then all
 260         available commands are printed. If a git command is named this
 261         option will bring up the manual page for that command.
 262 +
 263 Other options are available to control how the manual page is
 264 displayed. See linkgit:git-help[1] for more information,
 265 because `git --help ...` is converted internally into `git
 266 help ...`.
 267
 268 -c <name>=<value>::
 269         Pass a configuration parameter to the command. The value
 270         given will override values from configuration files.
 271         The <name> is expected in the same format as listed by
 272         'git config' (subkeys separated by dots).
 273
 274 --exec-path[=<path>]::
 275         Path to wherever your core git programs are installed.
 276         This can also be controlled by setting the GIT_EXEC_PATH
 277         environment variable. If no path is given, 'git' will print
 278         the current setting and then exit.
 279
 280 --html-path::
 281         Print the path to wherever your git HTML documentation is installed
 282         and exit.
 283
 284 -p::
 285 --paginate::
 286         Pipe all output into 'less' (or if set, $PAGER) if standard
 287         output is a terminal.  This overrides the `pager.<cmd>`
 288         configuration options (see the "Configuration Mechanism" section
 289         below).
 290
 291 --no-pager::
 292         Do not pipe git output into a pager.
 293
 294 --git-dir=<path>::
 295         Set the path to the repository. This can also be controlled by
 296         setting the GIT_DIR environment variable. It can be an absolute
 297         path or relative path to current working directory.
 298
 299 --work-tree=<path>::
 300         Set the path to the working tree. It can be an absolute path
 301         or a path relative to the current working directory.
 302         This can also be controlled by setting the GIT_WORK_TREE
 303         environment variable and the core.worktree configuration
 304         variable (see core.worktree in linkgit:git-config[1] for a
 305         more detailed discussion).
 306
 307 --bare::
 308         Treat the repository as a bare repository.  If GIT_DIR
 309         environment is not set, it is set to the current working
 310         directory.
 311
 312 --no-replace-objects::
 313         Do not use replacement refs to replace git objects. See
 314         linkgit:git-replace[1] for more information.
 315
 316
 317 FURTHER DOCUMENTATION
 318 ---------------------
 319
 320 See the references above to get started using git.  The following is
 321 probably more detail than necessary for a first-time user.
 322
 323 The link:user-manual.html#git-concepts[git concepts chapter of the
 324 user-manual] and linkgit:gitcore-tutorial[7] both provide
 325 introductions to the underlying git architecture.
 326
 327 See linkgit:gitworkflows[7] for an overview of recommended workflows.
 328
 329 See also the link:howto-index.html[howto] documents for some useful
 330 examples.
 331
 332 The internals are documented in the
 333 link:technical/api-index.html[GIT API documentation].
 334
 335 GIT COMMANDS
 336 ------------
 337
 338 We divide git into high level ("porcelain") commands and low level
 339 ("plumbing") commands.
 340
 341 High-level commands (porcelain)
 342 -------------------------------
 343
 344 We separate the porcelain commands into the main commands and some
 345 ancillary user utilities.
 346
 347 Main porcelain commands
 348 ~~~~~~~~~~~~~~~~~~~~~~~
 349
 350 include::cmds-mainporcelain.txt[]
 351
 352 Ancillary Commands
 353 ~~~~~~~~~~~~~~~~~~
 354 Manipulators:
 355
 356 include::cmds-ancillarymanipulators.txt[]
 357
 358 Interrogators:
 359
 360 include::cmds-ancillaryinterrogators.txt[]
 361
 362
 363 Interacting with Others
 364 ~~~~~~~~~~~~~~~~~~~~~~~
 365
 366 These commands are to interact with foreign SCM and with other
 367 people via patch over e-mail.
 368
 369 include::cmds-foreignscminterface.txt[]
 370
 371
 372 Low-level commands (plumbing)
 373 -----------------------------
 374
 375 Although git includes its
 376 own porcelain layer, its low-level commands are sufficient to support
 377 development of alternative porcelains.  Developers of such porcelains
 378 might start by reading about linkgit:git-update-index[1] and
 379 linkgit:git-read-tree[1].
 380
 381 The interface (input, output, set of options and the semantics)
 382 to these low-level commands are meant to be a lot more stable
 383 than Porcelain level commands, because these commands are
 384 primarily for scripted use.  The interface to Porcelain commands
 385 on the other hand are subject to change in order to improve the
 386 end user experience.
 387
 388 The following description divides
 389 the low-level commands into commands that manipulate objects (in
 390 the repository, index, and working tree), commands that interrogate and
 391 compare objects, and commands that move objects and references between
 392 repositories.
 393
 394
 395 Manipulation commands
 396 ~~~~~~~~~~~~~~~~~~~~~
 397
 398 include::cmds-plumbingmanipulators.txt[]
 399
 400
 401 Interrogation commands
 402 ~~~~~~~~~~~~~~~~~~~~~~
 403
 404 include::cmds-plumbinginterrogators.txt[]
 405
 406 In general, the interrogate commands do not touch the files in
 407 the working tree.
 408
 409
 410 Synching repositories
 411 ~~~~~~~~~~~~~~~~~~~~~
 412
 413 include::cmds-synchingrepositories.txt[]
 414
 415 The following are helper commands used by the above; end users
 416 typically do not use them directly.
 417
 418 include::cmds-synchelpers.txt[]
 419
 420
 421 Internal helper commands
 422 ~~~~~~~~~~~~~~~~~~~~~~~~
 423
 424 These are internal helper commands used by other commands; end
 425 users typically do not use them directly.
 426
 427 include::cmds-purehelpers.txt[]
 428
 429
 430 Configuration Mechanism
 431 -----------------------
 432
 433 Starting from 0.99.9 (actually mid 0.99.8.GIT), `.git/config` file
 434 is used to hold per-repository configuration options.  It is a
 435 simple text file modeled after `.ini` format familiar to some
 436 people.  Here is an example:
 437
 438 ------------
 439 #
 440 # A '#' or ';' character indicates a comment.
 441 #
 442
 443 ; core variables
 444 [core]
 445         ; Don't trust file modes
 446         filemode = false
 447
 448 ; user identity
 449 [user]
 450         name = "Junio C Hamano"
 451         email = "junkio@twinsun.com"
 452
 453 ------------
 454
 455 Various commands read from the configuration file and adjust
 456 their operation accordingly.  See linkgit:git-config[1] for a
 457 list.
 458
 459
 460 Identifier Terminology
 461 ----------------------
 462 <object>::
 463         Indicates the object name for any type of object.
 464
 465 <blob>::
 466         Indicates a blob object name.
 467
 468 <tree>::
 469         Indicates a tree object name.
 470
 471 <commit>::
 472         Indicates a commit object name.
 473
 474 <tree-ish>::
 475         Indicates a tree, commit or tag object name.  A
 476         command that takes a <tree-ish> argument ultimately wants to
 477         operate on a <tree> object but automatically dereferences
 478         <commit> and <tag> objects that point at a <tree>.
 479
 480 <commit-ish>::
 481         Indicates a commit or tag object name.  A
 482         command that takes a <commit-ish> argument ultimately wants to
 483         operate on a <commit> object but automatically dereferences
 484         <tag> objects that point at a <commit>.
 485
 486 <type>::
 487         Indicates that an object type is required.
 488         Currently one of: `blob`, `tree`, `commit`, or `tag`.
 489
 490 <file>::
 491         Indicates a filename - almost always relative to the
 492         root of the tree structure `GIT_INDEX_FILE` describes.
 493
 494 Symbolic Identifiers
 495 --------------------
 496 Any git command accepting any <object> can also use the following
 497 symbolic notation:
 498
 499 HEAD::
 500         indicates the head of the current branch (i.e. the
 501         contents of `$GIT_DIR/HEAD`).
 502
 503 <tag>::
 504         a valid tag 'name'
 505         (i.e. the contents of `$GIT_DIR/refs/tags/<tag>`).
 506
 507 <head>::
 508         a valid head 'name'
 509         (i.e. the contents of `$GIT_DIR/refs/heads/<head>`).
 510
 511 For a more complete list of ways to spell object names, see
 512 "SPECIFYING REVISIONS" section in linkgit:gitrevisions[7].
 513
 514
 515 File/Directory Structure
 516 ------------------------
 517
 518 Please see the linkgit:gitrepository-layout[5] document.
 519
 520 Read linkgit:githooks[5] for more details about each hook.
 521
 522 Higher level SCMs may provide and manage additional information in the
 523 `$GIT_DIR`.
 524
 525
 526 Terminology
 527 -----------
 528 Please see linkgit:gitglossary[7].
 529
 530
 531 Environment Variables
 532 ---------------------
 533 Various git commands use the following environment variables:
 534
 535 The git Repository
 536 ~~~~~~~~~~~~~~~~~~
 537 These environment variables apply to 'all' core git commands. Nb: it
 538 is worth noting that they may be used/overridden by SCMS sitting above
 539 git so take care if using Cogito etc.
 540
 541 'GIT_INDEX_FILE'::
 542         This environment allows the specification of an alternate
 543         index file. If not specified, the default of `$GIT_DIR/index`
 544         is used.
 545
 546 'GIT_OBJECT_DIRECTORY'::
 547         If the object storage directory is specified via this
 548         environment variable then the sha1 directories are created
 549         underneath - otherwise the default `$GIT_DIR/objects`
 550         directory is used.
 551
 552 'GIT_ALTERNATE_OBJECT_DIRECTORIES'::
 553         Due to the immutable nature of git objects, old objects can be
 554         archived into shared, read-only directories. This variable
 555         specifies a ":" separated (on Windows ";" separated) list
 556         of git object directories which can be used to search for git
 557         objects. New objects will not be written to these directories.
 558
 559 'GIT_DIR'::
 560         If the 'GIT_DIR' environment variable is set then it
 561         specifies a path to use instead of the default `.git`
 562         for the base of the repository.
 563
 564 'GIT_WORK_TREE'::
 565         Set the path to the working tree.  The value will not be
 566         used in combination with repositories found automatically in
 567         a .git directory (i.e. $GIT_DIR is not set).
 568         This can also be controlled by the '--work-tree' command line
 569         option and the core.worktree configuration variable.
 570
 571 'GIT_CEILING_DIRECTORIES'::
 572         This should be a colon-separated list of absolute paths.
 573         If set, it is a list of directories that git should not chdir
 574         up into while looking for a repository directory.
 575         It will not exclude the current working directory or
 576         a GIT_DIR set on the command line or in the environment.
 577         (Useful for excluding slow-loading network directories.)
 578
 579 'GIT_DISCOVERY_ACROSS_FILESYSTEM'::
 580         When run in a directory that does not have ".git" repository
 581         directory, git tries to find such a directory in the parent
 582         directories to find the top of the working tree, but by default it
 583         does not cross filesystem boundaries.  This environment variable
 584         can be set to true to tell git not to stop at filesystem
 585         boundaries.  Like 'GIT_CEILING_DIRECTORIES', this will not affect
 586         an explicit repository directory set via 'GIT_DIR' or on the
 587         command line.
 588
 589 git Commits
 590 ~~~~~~~~~~~
 591 'GIT_AUTHOR_NAME'::
 592 'GIT_AUTHOR_EMAIL'::
 593 'GIT_AUTHOR_DATE'::
 594 'GIT_COMMITTER_NAME'::
 595 'GIT_COMMITTER_EMAIL'::
 596 'GIT_COMMITTER_DATE'::
 597 'EMAIL'::
 598         see linkgit:git-commit-tree[1]
 599
 600 git Diffs
 601 ~~~~~~~~~
 602 'GIT_DIFF_OPTS'::
 603         Only valid setting is "--unified=??" or "-u??" to set the
 604         number of context lines shown when a unified diff is created.
 605         This takes precedence over any "-U" or "--unified" option
 606         value passed on the git diff command line.
 607
 608 'GIT_EXTERNAL_DIFF'::
 609         When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
 610         program named by it is called, instead of the diff invocation
 611         described above.  For a path that is added, removed, or modified,
 612         'GIT_EXTERNAL_DIFF' is called with 7 parameters:
 613
 614         path old-file old-hex old-mode new-file new-hex new-mode
 615 +
 616 where:
 617
 618         <old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
 619                          contents of <old|new>,
 620         <old|new>-hex:: are the 40-hexdigit SHA1 hashes,
 621         <old|new>-mode:: are the octal representation of the file modes.
 622
 623 +
 624 The file parameters can point at the user's working file
 625 (e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
 626 when a new file is added), or a temporary file (e.g. `old-file` in the
 627 index).  'GIT_EXTERNAL_DIFF' should not worry about unlinking the
 628 temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
 629 +
 630 For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
 631 parameter, <path>.
 632
 633 other
 634 ~~~~~
 635 'GIT_MERGE_VERBOSITY'::
 636         A number controlling the amount of output shown by
 637         the recursive merge strategy.  Overrides merge.verbosity.
 638         See linkgit:git-merge[1]
 639
 640 'GIT_PAGER'::
 641         This environment variable overrides `$PAGER`. If it is set
 642         to an empty string or to the value "cat", git will not launch
 643         a pager.  See also the `core.pager` option in
 644         linkgit:git-config[1].
 645
 646 'GIT_SSH'::
 647         If this environment variable is set then 'git fetch'
 648         and 'git push' will use this command instead
 649         of 'ssh' when they need to connect to a remote system.
 650         The '$GIT_SSH' command will be given exactly two arguments:
 651         the 'username@host' (or just 'host') from the URL and the
 652         shell command to execute on that remote system.
 653 +
 654 To pass options to the program that you want to list in GIT_SSH
 655 you will need to wrap the program and options into a shell script,
 656 then set GIT_SSH to refer to the shell script.
 657 +
 658 Usually it is easier to configure any desired options through your
 659 personal `.ssh/config` file.  Please consult your ssh documentation
 660 for further details.
 661
 662 'GIT_ASKPASS'::
 663         If this environment variable is set, then git commands which need to
 664         acquire passwords or passphrases (e.g. for HTTP or IMAP authentication)
 665         will call this program with a suitable prompt as command line argument
 666         and read the password from its STDOUT. See also the 'core.askpass'
 667         option in linkgit:git-config[1].
 668
 669 'GIT_FLUSH'::
 670         If this environment variable is set to "1", then commands such
 671         as 'git blame' (in incremental mode), 'git rev-list', 'git log',
 672         and 'git whatchanged' will force a flush of the output stream
 673         after each commit-oriented record have been flushed.   If this
 674         variable is set to "0", the output of these commands will be done
 675         using completely buffered I/O.   If this environment variable is
 676         not set, git will choose buffered or record-oriented flushing
 677         based on whether stdout appears to be redirected to a file or not.
 678
 679 'GIT_TRACE'::
 680         If this variable is set to "1", "2" or "true" (comparison
 681         is case insensitive), git will print `trace:` messages on
 682         stderr telling about alias expansion, built-in command
 683         execution and external command execution.
 684         If this variable is set to an integer value greater than 1
 685         and lower than 10 (strictly) then git will interpret this
 686         value as an open file descriptor and will try to write the
 687         trace messages into this file descriptor.
 688         Alternatively, if this variable is set to an absolute path
 689         (starting with a '/' character), git will interpret this
 690         as a file path and will try to write the trace messages
 691         into it.
 692
 693 Discussion[[Discussion]]
 694 ------------------------
 695
 696 More detail on the following is available from the
 697 link:user-manual.html#git-concepts[git concepts chapter of the
 698 user-manual] and linkgit:gitcore-tutorial[7].
 699
 700 A git project normally consists of a working directory with a ".git"
 701 subdirectory at the top level.  The .git directory contains, among other
 702 things, a compressed object database representing the complete history
 703 of the project, an "index" file which links that history to the current
 704 contents of the working tree, and named pointers into that history such
 705 as tags and branch heads.
 706
 707 The object database contains objects of three main types: blobs, which
 708 hold file data; trees, which point to blobs and other trees to build up
 709 directory hierarchies; and commits, which each reference a single tree
 710 and some number of parent commits.
 711
 712 The commit, equivalent to what other systems call a "changeset" or
 713 "version", represents a step in the project's history, and each parent
 714 represents an immediately preceding step.  Commits with more than one
 715 parent represent merges of independent lines of development.
 716
 717 All objects are named by the SHA1 hash of their contents, normally
 718 written as a string of 40 hex digits.  Such names are globally unique.
 719 The entire history leading up to a commit can be vouched for by signing
 720 just that commit.  A fourth object type, the tag, is provided for this
 721 purpose.
 722
 723 When first created, objects are stored in individual files, but for
 724 efficiency may later be compressed together into "pack files".
 725
 726 Named pointers called refs mark interesting points in history.  A ref
 727 may contain the SHA1 name of an object or the name of another ref.  Refs
 728 with names beginning `ref/head/` contain the SHA1 name of the most
 729 recent commit (or "head") of a branch under development.  SHA1 names of
 730 tags of interest are stored under `ref/tags/`.  A special ref named
 731 `HEAD` contains the name of the currently checked-out branch.
 732
 733 The index file is initialized with a list of all paths and, for each
 734 path, a blob object and a set of attributes.  The blob object represents
 735 the contents of the file as of the head of the current branch.  The
 736 attributes (last modified time, size, etc.) are taken from the
 737 corresponding file in the working tree.  Subsequent changes to the
 738 working tree can be found by comparing these attributes.  The index may
 739 be updated with new content, and new commits may be created from the
 740 content stored in the index.
 741
 742 The index is also capable of storing multiple entries (called "stages")
 743 for a given pathname.  These stages are used to hold the various
 744 unmerged version of a file when a merge is in progress.
 745
 746 Authors
 747 -------
 748 Git was started by Linus Torvalds, and is currently maintained by Junio
 749 C Hamano. Numerous contributions have come from the git mailing list
 750 <git@vger.kernel.org>. For a more complete list of contributors, see
 751 http://git-scm.com/about. If you have a clone of git.git itself, the
 752 output of linkgit:git-shortlog[1] and linkgit:git-blame[1] can show you
 753 the authors for specific parts of the project.
 754
 755 Reporting Bugs
 756 --------------
 757
 758 Report bugs to the Git mailing list <git@vger.kernel.org> where the
 759 development and maintenance is primarily done.  You do not have to be
 760 subscribed to the list to send a message there.
 761
 762 SEE ALSO
 763 --------
 764 linkgit:gittutorial[7], linkgit:gittutorial-2[7],
 765 link:everyday.html[Everyday Git], linkgit:gitcvs-migration[7],
 766 linkgit:gitglossary[7], linkgit:gitcore-tutorial[7],
 767 linkgit:gitcli[7], link:user-manual.html[The Git User's Manual],
 768 linkgit:gitworkflows[7]
 769
 770 GIT
 771 ---
 772 Part of the linkgit:git[1] suite