1[[def_alternate_object_database]]alternate object database:: 2 Via the alternates mechanism, a <<def_repository,repository>> 3 can inherit part of its <<def_object_database,object database>> 4 from another object database, which is called an "alternate". 5 6[[def_bare_repository]]bare repository:: 7 A bare repository is normally an appropriately 8 named <<def_directory,directory>> with a `.git` suffix that does not 9 have a locally checked-out copy of any of the files under 10 revision control. That is, all of the Git 11 administrative and control files that would normally be present in the 12 hidden `.git` sub-directory are directly present in the 13 `repository.git` directory instead, 14 and no other files are present and checked out. Usually publishers of 15 public repositories make bare repositories available. 16 17[[def_blob_object]]blob object:: 18 Untyped <<def_object,object>>, e.g. the contents of a file. 19 20[[def_branch]]branch:: 21 A "branch" is an active line of development. The most recent 22 <<def_commit,commit>> on a branch is referred to as the tip of 23 that branch. The tip of the branch is referenced by a branch 24 <<def_head,head>>, which moves forward as additional development 25 is done on the branch. A single Git 26 <<def_repository,repository>> can track an arbitrary number of 27 branches, but your <<def_working_tree,working tree>> is 28 associated with just one of them (the "current" or "checked out" 29 branch), and <<def_HEAD,HEAD>> points to that branch. 30 31[[def_cache]]cache:: 32 Obsolete for: <<def_index,index>>. 33 34[[def_chain]]chain:: 35 A list of objects, where each <<def_object,object>> in the list contains 36 a reference to its successor (for example, the successor of a 37 <<def_commit,commit>> could be one of its <<def_parent,parents>>). 38 39[[def_changeset]]changeset:: 40 BitKeeper/cvsps speak for "<<def_commit,commit>>". Since Git does not 41 store changes, but states, it really does not make sense to use the term 42 "changesets" with Git. 43 44[[def_checkout]]checkout:: 45 The action of updating all or part of the 46 <<def_working_tree,working tree>> with a <<def_tree_object,tree object>> 47 or <<def_blob_object,blob>> from the 48 <<def_object_database,object database>>, and updating the 49 <<def_index,index>> and <<def_HEAD,HEAD>> if the whole working tree has 50 been pointed at a new <<def_branch,branch>>. 51 52[[def_cherry-picking]]cherry-picking:: 53 In <<def_SCM,SCM>> jargon, "cherry pick" means to choose a subset of 54 changes out of a series of changes (typically commits) and record them 55 as a new series of changes on top of a different codebase. In Git, this is 56 performed by the "git cherry-pick" command to extract the change introduced 57 by an existing <<def_commit,commit>> and to record it based on the tip 58 of the current <<def_branch,branch>> as a new commit. 59 60[[def_clean]]clean:: 61 A <<def_working_tree,working tree>> is clean, if it 62 corresponds to the <<def_revision,revision>> referenced by the current 63 <<def_head,head>>. Also see "<<def_dirty,dirty>>". 64 65[[def_commit]]commit:: 66 As a noun: A single point in the 67 Git history; the entire history of a project is represented as a 68 set of interrelated commits. The word "commit" is often 69 used by Git in the same places other revision control systems 70 use the words "revision" or "version". Also used as a short 71 hand for <<def_commit_object,commit object>>. 72+ 73As a verb: The action of storing a new snapshot of the project's 74state in the Git history, by creating a new commit representing the current 75state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>> 76to point at the new commit. 77 78[[def_commit_object]]commit object:: 79 An <<def_object,object>> which contains the information about a 80 particular <<def_revision,revision>>, such as <<def_parent,parents>>, committer, 81 author, date and the <<def_tree_object,tree object>> which corresponds 82 to the top <<def_directory,directory>> of the stored 83 revision. 84 85[[def_commit-ish]]commit-ish (also committish):: 86 A <<def_commit_object,commit object>> or an 87 <<def_object,object>> that can be recursively dereferenced to 88 a commit object. 89 The following are all commit-ishes: 90 a commit object, 91 a <<def_tag_object,tag object>> that points to a commit 92 object, 93 a tag object that points to a tag object that points to a 94 commit object, 95 etc. 96 97[[def_core_git]]core Git:: 98 Fundamental data structures and utilities of Git. Exposes only limited 99 source code management tools. 100 101[[def_DAG]]DAG:: 102 Directed acyclic graph. The <<def_commit_object,commit objects>> form a 103 directed acyclic graph, because they have parents (directed), and the 104 graph of commit objects is acyclic (there is no <<def_chain,chain>> 105 which begins and ends with the same <<def_object,object>>). 106 107[[def_dangling_object]]dangling object:: 108 An <<def_unreachable_object,unreachable object>> which is not 109 <<def_reachable,reachable>> even from other unreachable objects; a 110 dangling object has no references to it from any 111 reference or <<def_object,object>> in the <<def_repository,repository>>. 112 113[[def_detached_HEAD]]detached HEAD:: 114 Normally the <<def_HEAD,HEAD>> stores the name of a 115 <<def_branch,branch>>, and commands that operate on the 116 history HEAD represents operate on the history leading to the 117 tip of the branch the HEAD points at. However, Git also 118 allows you to <<def_checkout,check out>> an arbitrary 119 <<def_commit,commit>> that isn't necessarily the tip of any 120 particular branch. The HEAD in such a state is called 121 "detached". 122+ 123Note that commands that operate on the history of the current branch 124(e.g. `git commit` to build a new history on top of it) still work 125while the HEAD is detached. They update the HEAD to point at the tip 126of the updated history without affecting any branch. Commands that 127update or inquire information _about_ the current branch (e.g. `git 128branch --set-upstream-to` that sets what remote-tracking branch the 129current branch integrates with) obviously do not work, as there is no 130(real) current branch to ask about in this state. 131 132[[def_directory]]directory:: 133 The list you get with "ls" :-) 134 135[[def_dirty]]dirty:: 136 A <<def_working_tree,working tree>> is said to be "dirty" if 137 it contains modifications which have not been <<def_commit,committed>> to the current 138 <<def_branch,branch>>. 139 140[[def_evil_merge]]evil merge:: 141 An evil merge is a <<def_merge,merge>> that introduces changes that 142 do not appear in any <<def_parent,parent>>. 143 144[[def_fast_forward]]fast-forward:: 145 A fast-forward is a special type of <<def_merge,merge>> where you have a 146 <<def_revision,revision>> and you are "merging" another 147 <<def_branch,branch>>'s changes that happen to be a descendant of what 148 you have. In such a case, you do not make a new <<def_merge,merge>> 149 <<def_commit,commit>> but instead just update to his 150 revision. This will happen frequently on a 151 <<def_remote_tracking_branch,remote-tracking branch>> of a remote 152 <<def_repository,repository>>. 153 154[[def_fetch]]fetch:: 155 Fetching a <<def_branch,branch>> means to get the 156 branch's <<def_head_ref,head ref>> from a remote 157 <<def_repository,repository>>, to find out which objects are 158 missing from the local <<def_object_database,object database>>, 159 and to get them, too. See also linkgit:git-fetch[1]. 160 161[[def_file_system]]file system:: 162 Linus Torvalds originally designed Git to be a user space file system, 163 i.e. the infrastructure to hold files and directories. That ensured the 164 efficiency and speed of Git. 165 166[[def_git_archive]]Git archive:: 167 Synonym for <<def_repository,repository>> (for arch people). 168 169[[def_gitfile]]gitfile:: 170 A plain file `.git` at the root of a working tree that 171 points at the directory that is the real repository. 172 173[[def_grafts]]grafts:: 174 Grafts enables two otherwise different lines of development to be joined 175 together by recording fake ancestry information for commits. This way 176 you can make Git pretend the set of <<def_parent,parents>> a <<def_commit,commit>> has 177 is different from what was recorded when the commit was 178 created. Configured via the `.git/info/grafts` file. 179+ 180Note that the grafts mechanism is outdated and can lead to problems 181transferring objects between repositories; see linkgit:git-replace[1] 182for a more flexible and robust system to do the same thing. 183 184[[def_hash]]hash:: 185 In Git's context, synonym for <<def_object_name,object name>>. 186 187[[def_head]]head:: 188 A <<def_ref,named reference>> to the <<def_commit,commit>> at the tip of a 189 <<def_branch,branch>>. Heads are stored in a file in 190 `$GIT_DIR/refs/heads/` directory, except when using packed refs. (See 191 linkgit:git-pack-refs[1].) 192 193[[def_HEAD]]HEAD:: 194 The current <<def_branch,branch>>. In more detail: Your <<def_working_tree, 195 working tree>> is normally derived from the state of the tree 196 referred to by HEAD. HEAD is a reference to one of the 197 <<def_head,heads>> in your repository, except when using a 198 <<def_detached_HEAD,detached HEAD>>, in which case it directly 199 references an arbitrary commit. 200 201[[def_head_ref]]head ref:: 202 A synonym for <<def_head,head>>. 203 204[[def_hook]]hook:: 205 During the normal execution of several Git commands, call-outs are made 206 to optional scripts that allow a developer to add functionality or 207 checking. Typically, the hooks allow for a command to be pre-verified 208 and potentially aborted, and allow for a post-notification after the 209 operation is done. The hook scripts are found in the 210 `$GIT_DIR/hooks/` directory, and are enabled by simply 211 removing the `.sample` suffix from the filename. In earlier versions 212 of Git you had to make them executable. 213 214[[def_index]]index:: 215 A collection of files with stat information, whose contents are stored 216 as objects. The index is a stored version of your 217 <<def_working_tree,working tree>>. Truth be told, it can also contain a second, and even 218 a third version of a working tree, which are used 219 when <<def_merge,merging>>. 220 221[[def_index_entry]]index entry:: 222 The information regarding a particular file, stored in the 223 <<def_index,index>>. An index entry can be unmerged, if a 224 <<def_merge,merge>> was started, but not yet finished (i.e. if 225 the index contains multiple versions of that file). 226 227[[def_master]]master:: 228 The default development <<def_branch,branch>>. Whenever you 229 create a Git <<def_repository,repository>>, a branch named 230 "master" is created, and becomes the active branch. In most 231 cases, this contains the local development, though that is 232 purely by convention and is not required. 233 234[[def_merge]]merge:: 235 As a verb: To bring the contents of another 236 <<def_branch,branch>> (possibly from an external 237 <<def_repository,repository>>) into the current branch. In the 238 case where the merged-in branch is from a different repository, 239 this is done by first <<def_fetch,fetching>> the remote branch 240 and then merging the result into the current branch. This 241 combination of fetch and merge operations is called a 242 <<def_pull,pull>>. Merging is performed by an automatic process 243 that identifies changes made since the branches diverged, and 244 then applies all those changes together. In cases where changes 245 conflict, manual intervention may be required to complete the 246 merge. 247+ 248As a noun: unless it is a <<def_fast_forward,fast-forward>>, a 249successful merge results in the creation of a new <<def_commit,commit>> 250representing the result of the merge, and having as 251<<def_parent,parents>> the tips of the merged <<def_branch,branches>>. 252This commit is referred to as a "merge commit", or sometimes just a 253"merge". 254 255[[def_object]]object:: 256 The unit of storage in Git. It is uniquely identified by the 257 <<def_SHA1,SHA-1>> of its contents. Consequently, an 258 object can not be changed. 259 260[[def_object_database]]object database:: 261 Stores a set of "objects", and an individual <<def_object,object>> is 262 identified by its <<def_object_name,object name>>. The objects usually 263 live in `$GIT_DIR/objects/`. 264 265[[def_object_identifier]]object identifier:: 266 Synonym for <<def_object_name,object name>>. 267 268[[def_object_name]]object name:: 269 The unique identifier of an <<def_object,object>>. The 270 object name is usually represented by a 40 character 271 hexadecimal string. Also colloquially called <<def_SHA1,SHA-1>>. 272 273[[def_object_type]]object type:: 274 One of the identifiers "<<def_commit_object,commit>>", 275 "<<def_tree_object,tree>>", "<<def_tag_object,tag>>" or 276 "<<def_blob_object,blob>>" describing the type of an 277 <<def_object,object>>. 278 279[[def_octopus]]octopus:: 280 To <<def_merge,merge>> more than two <<def_branch,branches>>. 281 282[[def_origin]]origin:: 283 The default upstream <<def_repository,repository>>. Most projects have 284 at least one upstream project which they track. By default 285 'origin' is used for that purpose. New upstream updates 286 will be fetched into <<def_remote_tracking_branch,remote-tracking branches>> named 287 origin/name-of-upstream-branch, which you can see using 288 `git branch -r`. 289 290[[def_pack]]pack:: 291 A set of objects which have been compressed into one file (to save space 292 or to transmit them efficiently). 293 294[[def_pack_index]]pack index:: 295 The list of identifiers, and other information, of the objects in a 296 <<def_pack,pack>>, to assist in efficiently accessing the contents of a 297 pack. 298 299[[def_pathspec]]pathspec:: 300 Pattern used to limit paths in Git commands. 301+ 302Pathspecs are used on the command line of "git ls-files", "git 303ls-tree", "git add", "git grep", "git diff", "git checkout", 304and many other commands to 305limit the scope of operations to some subset of the tree or 306worktree. See the documentation of each command for whether 307paths are relative to the current directory or toplevel. The 308pathspec syntax is as follows: 309+ 310-- 311 312* any path matches itself 313* the pathspec up to the last slash represents a 314 directory prefix. The scope of that pathspec is 315 limited to that subtree. 316* the rest of the pathspec is a pattern for the remainder 317 of the pathname. Paths relative to the directory 318 prefix will be matched against that pattern using fnmatch(3); 319 in particular, '*' and '?' _can_ match directory separators. 320 321-- 322+ 323For example, Documentation/*.jpg will match all .jpg files 324in the Documentation subtree, 325including Documentation/chapter_1/figure_1.jpg. 326+ 327A pathspec that begins with a colon `:` has special meaning. In the 328short form, the leading colon `:` is followed by zero or more "magic 329signature" letters (which optionally is terminated by another colon `:`), 330and the remainder is the pattern to match against the path. 331The "magic signature" consists of ASCII symbols that are neither 332alphanumeric, glob, regex special characters nor colon. 333The optional colon that terminates the "magic signature" can be 334omitted if the pattern begins with a character that does not belong to 335"magic signature" symbol set and is not a colon. 336+ 337In the long form, the leading colon `:` is followed by an open 338parenthesis `(`, a comma-separated list of zero or more "magic words", 339and a close parentheses `)`, and the remainder is the pattern to match 340against the path. 341+ 342A pathspec with only a colon means "there is no pathspec". This form 343should not be combined with other pathspec. 344+ 345-- 346top;; 347 The magic word `top` (magic signature: `/`) makes the pattern 348 match from the root of the working tree, even when you are 349 running the command from inside a subdirectory. 350 351literal;; 352 Wildcards in the pattern such as `*` or `?` are treated 353 as literal characters. 354 355icase;; 356 Case insensitive match. 357 358glob;; 359 Git treats the pattern as a shell glob suitable for 360 consumption by fnmatch(3) with the FNM_PATHNAME flag: 361 wildcards in the pattern will not match a / in the pathname. 362 For example, "Documentation/{asterisk}.html" matches 363 "Documentation/git.html" but not "Documentation/ppc/ppc.html" 364 or "tools/perf/Documentation/perf.html". 365+ 366Two consecutive asterisks ("`**`") in patterns matched against 367full pathname may have special meaning: 368 369 - A leading "`**`" followed by a slash means match in all 370 directories. For example, "`**/foo`" matches file or directory 371 "`foo`" anywhere, the same as pattern "`foo`". "`**/foo/bar`" 372 matches file or directory "`bar`" anywhere that is directly 373 under directory "`foo`". 374 375 - A trailing "`/**`" matches everything inside. For example, 376 "`abc/**`" matches all files inside directory "abc", relative 377 to the location of the `.gitignore` file, with infinite depth. 378 379 - A slash followed by two consecutive asterisks then a slash 380 matches zero or more directories. For example, "`a/**/b`" 381 matches "`a/b`", "`a/x/b`", "`a/x/y/b`" and so on. 382 383 - Other consecutive asterisks are considered invalid. 384+ 385Glob magic is incompatible with literal magic. 386 387attr;; 388After `attr:` comes a space separated list of "attribute 389requirements", all of which must be met in order for the 390path to be considered a match; this is in addition to the 391usual non-magic pathspec pattern matching. 392See linkgit:gitattributes[5]. 393+ 394Each of the attribute requirements for the path takes one of 395these forms: 396 397- "`ATTR`" requires that the attribute `ATTR` be set. 398 399- "`-ATTR`" requires that the attribute `ATTR` be unset. 400 401- "`ATTR=VALUE`" requires that the attribute `ATTR` be 402 set to the string `VALUE`. 403 404- "`!ATTR`" requires that the attribute `ATTR` be 405 unspecified. 406+ 407 408exclude;; 409 After a path matches any non-exclude pathspec, it will be run 410 through all exclude pathspecs (magic signature: `!` or its 411 synonym `^`). If it matches, the path is ignored. When there 412 is no non-exclude pathspec, the exclusion is applied to the 413 result set as if invoked without any pathspec. 414-- 415 416[[def_parent]]parent:: 417 A <<def_commit_object,commit object>> contains a (possibly empty) list 418 of the logical predecessor(s) in the line of development, i.e. its 419 parents. 420 421[[def_pickaxe]]pickaxe:: 422 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore 423 routines that help select changes that add or delete a given text 424 string. With the `--pickaxe-all` option, it can be used to view the full 425 <<def_changeset,changeset>> that introduced or removed, say, a 426 particular line of text. See linkgit:git-diff[1]. 427 428[[def_plumbing]]plumbing:: 429 Cute name for <<def_core_git,core Git>>. 430 431[[def_porcelain]]porcelain:: 432 Cute name for programs and program suites depending on 433 <<def_core_git,core Git>>, presenting a high level access to 434 core Git. Porcelains expose more of a <<def_SCM,SCM>> 435 interface than the <<def_plumbing,plumbing>>. 436 437[[def_per_worktree_ref]]per-worktree ref:: 438 Refs that are per-<<def_working_tree,worktree>>, rather than 439 global. This is presently only <<def_HEAD,HEAD>> and any refs 440 that start with `refs/bisect/`, but might later include other 441 unusual refs. 442 443[[def_pseudoref]]pseudoref:: 444 Pseudorefs are a class of files under `$GIT_DIR` which behave 445 like refs for the purposes of rev-parse, but which are treated 446 specially by git. Pseudorefs both have names that are all-caps, 447 and always start with a line consisting of a 448 <<def_SHA1,SHA-1>> followed by whitespace. So, HEAD is not a 449 pseudoref, because it is sometimes a symbolic ref. They might 450 optionally contain some additional data. `MERGE_HEAD` and 451 `CHERRY_PICK_HEAD` are examples. Unlike 452 <<def_per_worktree_ref,per-worktree refs>>, these files cannot 453 be symbolic refs, and never have reflogs. They also cannot be 454 updated through the normal ref update machinery. Instead, 455 they are updated by directly writing to the files. However, 456 they can be read as if they were refs, so `git rev-parse 457 MERGE_HEAD` will work. 458 459[[def_pull]]pull:: 460 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and 461 <<def_merge,merge>> it. See also linkgit:git-pull[1]. 462 463[[def_push]]push:: 464 Pushing a <<def_branch,branch>> means to get the branch's 465 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>, 466 find out if it is an ancestor to the branch's local 467 head ref, and in that case, putting all 468 objects, which are <<def_reachable,reachable>> from the local 469 head ref, and which are missing from the remote 470 repository, into the remote 471 <<def_object_database,object database>>, and updating the remote 472 head ref. If the remote <<def_head,head>> is not an 473 ancestor to the local head, the push fails. 474 475[[def_reachable]]reachable:: 476 All of the ancestors of a given <<def_commit,commit>> are said to be 477 "reachable" from that commit. More 478 generally, one <<def_object,object>> is reachable from 479 another if we can reach the one from the other by a <<def_chain,chain>> 480 that follows <<def_tag,tags>> to whatever they tag, 481 <<def_commit_object,commits>> to their parents or trees, and 482 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>> 483 that they contain. 484 485[[def_rebase]]rebase:: 486 To reapply a series of changes from a <<def_branch,branch>> to a 487 different base, and reset the <<def_head,head>> of that branch 488 to the result. 489 490[[def_ref]]ref:: 491 A name that begins with `refs/` (e.g. `refs/heads/master`) 492 that points to an <<def_object_name,object name>> or another 493 ref (the latter is called a <<def_symref,symbolic ref>>). 494 For convenience, a ref can sometimes be abbreviated when used 495 as an argument to a Git command; see linkgit:gitrevisions[7] 496 for details. 497 Refs are stored in the <<def_repository,repository>>. 498+ 499The ref namespace is hierarchical. 500Different subhierarchies are used for different purposes (e.g. the 501`refs/heads/` hierarchy is used to represent local branches). 502+ 503There are a few special-purpose refs that do not begin with `refs/`. 504The most notable example is `HEAD`. 505 506[[def_reflog]]reflog:: 507 A reflog shows the local "history" of a ref. In other words, 508 it can tell you what the 3rd last revision in _this_ repository 509 was, and what was the current state in _this_ repository, 510 yesterday 9:14pm. See linkgit:git-reflog[1] for details. 511 512[[def_refspec]]refspec:: 513 A "refspec" is used by <<def_fetch,fetch>> and 514 <<def_push,push>> to describe the mapping between remote 515 <<def_ref,ref>> and local ref. 516 517[[def_remote]]remote repository:: 518 A <<def_repository,repository>> which is used to track the same 519 project but resides somewhere else. To communicate with remotes, 520 see <<def_fetch,fetch>> or <<def_push,push>>. 521 522[[def_remote_tracking_branch]]remote-tracking branch:: 523 A <<def_ref,ref>> that is used to follow changes from another 524 <<def_repository,repository>>. It typically looks like 525 'refs/remotes/foo/bar' (indicating that it tracks a branch named 526 'bar' in a remote named 'foo'), and matches the right-hand-side of 527 a configured fetch <<def_refspec,refspec>>. A remote-tracking 528 branch should not contain direct modifications or have local 529 commits made to it. 530 531[[def_repository]]repository:: 532 A collection of <<def_ref,refs>> together with an 533 <<def_object_database,object database>> containing all objects 534 which are <<def_reachable,reachable>> from the refs, possibly 535 accompanied by meta data from one or more <<def_porcelain,porcelains>>. A 536 repository can share an object database with other repositories 537 via <<def_alternate_object_database,alternates mechanism>>. 538 539[[def_resolve]]resolve:: 540 The action of fixing up manually what a failed automatic 541 <<def_merge,merge>> left behind. 542 543[[def_revision]]revision:: 544 Synonym for <<def_commit,commit>> (the noun). 545 546[[def_rewind]]rewind:: 547 To throw away part of the development, i.e. to assign the 548 <<def_head,head>> to an earlier <<def_revision,revision>>. 549 550[[def_SCM]]SCM:: 551 Source code management (tool). 552 553[[def_SHA1]]SHA-1:: 554 "Secure Hash Algorithm 1"; a cryptographic hash function. 555 In the context of Git used as a synonym for <<def_object_name,object name>>. 556 557[[def_shallow_clone]]shallow clone:: 558 Mostly a synonym to <<def_shallow_repository,shallow repository>> 559 but the phrase makes it more explicit that it was created by 560 running `git clone --depth=...` command. 561 562[[def_shallow_repository]]shallow repository:: 563 A shallow <<def_repository,repository>> has an incomplete 564 history some of whose <<def_commit,commits>> have <<def_parent,parents>> cauterized away (in other 565 words, Git is told to pretend that these commits do not have the 566 parents, even though they are recorded in the <<def_commit_object,commit 567 object>>). This is sometimes useful when you are interested only in the 568 recent history of a project even though the real history recorded in the 569 upstream is much larger. A shallow repository 570 is created by giving the `--depth` option to linkgit:git-clone[1], and 571 its history can be later deepened with linkgit:git-fetch[1]. 572 573[[def_stash]]stash entry:: 574 An <<def_object,object>> used to temporarily store the contents of a 575 <<def_dirty,dirty>> working directory and the index for future reuse. 576 577[[def_submodule]]submodule:: 578 A <<def_repository,repository>> that holds the history of a 579 separate project inside another repository (the latter of 580 which is called <<def_superproject, superproject>>). 581 582[[def_superproject]]superproject:: 583 A <<def_repository,repository>> that references repositories 584 of other projects in its working tree as <<def_submodule,submodules>>. 585 The superproject knows about the names of (but does not hold 586 copies of) commit objects of the contained submodules. 587 588[[def_symref]]symref:: 589 Symbolic reference: instead of containing the <<def_SHA1,SHA-1>> 590 id itself, it is of the format 'ref: refs/some/thing' and when 591 referenced, it recursively dereferences to this reference. 592 '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic 593 references are manipulated with the linkgit:git-symbolic-ref[1] 594 command. 595 596[[def_tag]]tag:: 597 A <<def_ref,ref>> under `refs/tags/` namespace that points to an 598 object of an arbitrary type (typically a tag points to either a 599 <<def_tag_object,tag>> or a <<def_commit_object,commit object>>). 600 In contrast to a <<def_head,head>>, a tag is not updated by 601 the `commit` command. A Git tag has nothing to do with a Lisp 602 tag (which would be called an <<def_object_type,object type>> 603 in Git's context). A tag is most typically used to mark a particular 604 point in the commit ancestry <<def_chain,chain>>. 605 606[[def_tag_object]]tag object:: 607 An <<def_object,object>> containing a <<def_ref,ref>> pointing to 608 another object, which can contain a message just like a 609 <<def_commit_object,commit object>>. It can also contain a (PGP) 610 signature, in which case it is called a "signed tag object". 611 612[[def_topic_branch]]topic branch:: 613 A regular Git <<def_branch,branch>> that is used by a developer to 614 identify a conceptual line of development. Since branches are very easy 615 and inexpensive, it is often desirable to have several small branches 616 that each contain very well defined concepts or small incremental yet 617 related changes. 618 619[[def_tree]]tree:: 620 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree 621 object>> together with the dependent <<def_blob_object,blob>> and tree objects 622 (i.e. a stored representation of a working tree). 623 624[[def_tree_object]]tree object:: 625 An <<def_object,object>> containing a list of file names and modes along 626 with refs to the associated blob and/or tree objects. A 627 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>. 628 629[[def_tree-ish]]tree-ish (also treeish):: 630 A <<def_tree_object,tree object>> or an <<def_object,object>> 631 that can be recursively dereferenced to a tree object. 632 Dereferencing a <<def_commit_object,commit object>> yields the 633 tree object corresponding to the <<def_revision,revision>>'s 634 top <<def_directory,directory>>. 635 The following are all tree-ishes: 636 a <<def_commit-ish,commit-ish>>, 637 a tree object, 638 a <<def_tag_object,tag object>> that points to a tree object, 639 a tag object that points to a tag object that points to a tree 640 object, 641 etc. 642 643[[def_unmerged_index]]unmerged index:: 644 An <<def_index,index>> which contains unmerged 645 <<def_index_entry,index entries>>. 646 647[[def_unreachable_object]]unreachable object:: 648 An <<def_object,object>> which is not <<def_reachable,reachable>> from a 649 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference. 650 651[[def_upstream_branch]]upstream branch:: 652 The default <<def_branch,branch>> that is merged into the branch in 653 question (or the branch in question is rebased onto). It is configured 654 via branch.<name>.remote and branch.<name>.merge. If the upstream branch 655 of 'A' is 'origin/B' sometimes we say "'A' is tracking 'origin/B'". 656 657[[def_working_tree]]working tree:: 658 The tree of actual checked out files. The working tree normally 659 contains the contents of the <<def_HEAD,HEAD>> commit's tree, 660 plus any local changes that you have made but not yet committed.