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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 +
73 As a verb: The action of storing a new snapshot of the project's
74 state in the Git history, by creating a new commit representing the current
75 state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>>
76 to 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 +
123 Note 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
125 while the HEAD is detached. They update the HEAD to point at the tip
126 of the updated history without affecting any branch. Commands that
127 update or inquire information _about_ the current branch (e.g. `git
128 branch --set-upstream-to` that sets what remote-tracking branch the
129 current 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 +
180 Note that the grafts mechanism is outdated and can lead to problems
181 transferring objects between repositories; see linkgit:git-replace[1]
182 for 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 +
248 As a noun: unless it is a <<def_fast_forward,fast-forward>>, a
249 successful merge results in the creation of a new <<def_commit,commit>>
250 representing the result of the merge, and having as
251 <<def_parent,parents>> the tips of the merged <<def_branch,branches>>.
252 This 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_overlay]]overlay::
291 Only update and add files to the working directory, but don't
292 delete them, similar to how 'cp -R' would update the contents
293 in the destination directory. This is the default mode in a
294 <<def_checkout,checkout>> when checking out files from the
295 <<def_index,index>> or a <<def_tree-ish,tree-ish>>. In
296 contrast, no-overlay mode also deletes tracked files not
297 present in the source, similar to 'rsync --delete'.
298
299 [[def_pack]]pack::
300 A set of objects which have been compressed into one file (to save space
301 or to transmit them efficiently).
302
303 [[def_pack_index]]pack index::
304 The list of identifiers, and other information, of the objects in a
305 <<def_pack,pack>>, to assist in efficiently accessing the contents of a
306 pack.
307
308 [[def_pathspec]]pathspec::
309 Pattern used to limit paths in Git commands.
310 +
311 Pathspecs are used on the command line of "git ls-files", "git
312 ls-tree", "git add", "git grep", "git diff", "git checkout",
313 and many other commands to
314 limit the scope of operations to some subset of the tree or
315 worktree. See the documentation of each command for whether
316 paths are relative to the current directory or toplevel. The
317 pathspec syntax is as follows:
318 +
319 --
320
321 * any path matches itself
322 * the pathspec up to the last slash represents a
323 directory prefix. The scope of that pathspec is
324 limited to that subtree.
325 * the rest of the pathspec is a pattern for the remainder
326 of the pathname. Paths relative to the directory
327 prefix will be matched against that pattern using fnmatch(3);
328 in particular, '*' and '?' _can_ match directory separators.
329
330 --
331 +
332 For example, Documentation/*.jpg will match all .jpg files
333 in the Documentation subtree,
334 including Documentation/chapter_1/figure_1.jpg.
335 +
336 A pathspec that begins with a colon `:` has special meaning. In the
337 short form, the leading colon `:` is followed by zero or more "magic
338 signature" letters (which optionally is terminated by another colon `:`),
339 and the remainder is the pattern to match against the path.
340 The "magic signature" consists of ASCII symbols that are neither
341 alphanumeric, glob, regex special characters nor colon.
342 The optional colon that terminates the "magic signature" can be
343 omitted if the pattern begins with a character that does not belong to
344 "magic signature" symbol set and is not a colon.
345 +
346 In the long form, the leading colon `:` is followed by an open
347 parenthesis `(`, a comma-separated list of zero or more "magic words",
348 and a close parentheses `)`, and the remainder is the pattern to match
349 against the path.
350 +
351 A pathspec with only a colon means "there is no pathspec". This form
352 should not be combined with other pathspec.
353 +
354 --
355 top;;
356 The magic word `top` (magic signature: `/`) makes the pattern
357 match from the root of the working tree, even when you are
358 running the command from inside a subdirectory.
359
360 literal;;
361 Wildcards in the pattern such as `*` or `?` are treated
362 as literal characters.
363
364 icase;;
365 Case insensitive match.
366
367 glob;;
368 Git treats the pattern as a shell glob suitable for
369 consumption by fnmatch(3) with the FNM_PATHNAME flag:
370 wildcards in the pattern will not match a / in the pathname.
371 For example, "Documentation/{asterisk}.html" matches
372 "Documentation/git.html" but not "Documentation/ppc/ppc.html"
373 or "tools/perf/Documentation/perf.html".
374 +
375 Two consecutive asterisks ("`**`") in patterns matched against
376 full pathname may have special meaning:
377
378 - A leading "`**`" followed by a slash means match in all
379 directories. For example, "`**/foo`" matches file or directory
380 "`foo`" anywhere, the same as pattern "`foo`". "`**/foo/bar`"
381 matches file or directory "`bar`" anywhere that is directly
382 under directory "`foo`".
383
384 - A trailing "`/**`" matches everything inside. For example,
385 "`abc/**`" matches all files inside directory "abc", relative
386 to the location of the `.gitignore` file, with infinite depth.
387
388 - A slash followed by two consecutive asterisks then a slash
389 matches zero or more directories. For example, "`a/**/b`"
390 matches "`a/b`", "`a/x/b`", "`a/x/y/b`" and so on.
391
392 - Other consecutive asterisks are considered invalid.
393 +
394 Glob magic is incompatible with literal magic.
395
396 attr;;
397 After `attr:` comes a space separated list of "attribute
398 requirements", all of which must be met in order for the
399 path to be considered a match; this is in addition to the
400 usual non-magic pathspec pattern matching.
401 See linkgit:gitattributes[5].
402 +
403 Each of the attribute requirements for the path takes one of
404 these forms:
405
406 - "`ATTR`" requires that the attribute `ATTR` be set.
407
408 - "`-ATTR`" requires that the attribute `ATTR` be unset.
409
410 - "`ATTR=VALUE`" requires that the attribute `ATTR` be
411 set to the string `VALUE`.
412
413 - "`!ATTR`" requires that the attribute `ATTR` be
414 unspecified.
415 +
416 Note that when matching against a tree object, attributes are still
417 obtained from working tree, not from the given tree object.
418
419 exclude;;
420 After a path matches any non-exclude pathspec, it will be run
421 through all exclude pathspecs (magic signature: `!` or its
422 synonym `^`). If it matches, the path is ignored. When there
423 is no non-exclude pathspec, the exclusion is applied to the
424 result set as if invoked without any pathspec.
425 --
426
427 [[def_parent]]parent::
428 A <<def_commit_object,commit object>> contains a (possibly empty) list
429 of the logical predecessor(s) in the line of development, i.e. its
430 parents.
431
432 [[def_pickaxe]]pickaxe::
433 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore
434 routines that help select changes that add or delete a given text
435 string. With the `--pickaxe-all` option, it can be used to view the full
436 <<def_changeset,changeset>> that introduced or removed, say, a
437 particular line of text. See linkgit:git-diff[1].
438
439 [[def_plumbing]]plumbing::
440 Cute name for <<def_core_git,core Git>>.
441
442 [[def_porcelain]]porcelain::
443 Cute name for programs and program suites depending on
444 <<def_core_git,core Git>>, presenting a high level access to
445 core Git. Porcelains expose more of a <<def_SCM,SCM>>
446 interface than the <<def_plumbing,plumbing>>.
447
448 [[def_per_worktree_ref]]per-worktree ref::
449 Refs that are per-<<def_working_tree,worktree>>, rather than
450 global. This is presently only <<def_HEAD,HEAD>> and any refs
451 that start with `refs/bisect/`, but might later include other
452 unusual refs.
453
454 [[def_pseudoref]]pseudoref::
455 Pseudorefs are a class of files under `$GIT_DIR` which behave
456 like refs for the purposes of rev-parse, but which are treated
457 specially by git. Pseudorefs both have names that are all-caps,
458 and always start with a line consisting of a
459 <<def_SHA1,SHA-1>> followed by whitespace. So, HEAD is not a
460 pseudoref, because it is sometimes a symbolic ref. They might
461 optionally contain some additional data. `MERGE_HEAD` and
462 `CHERRY_PICK_HEAD` are examples. Unlike
463 <<def_per_worktree_ref,per-worktree refs>>, these files cannot
464 be symbolic refs, and never have reflogs. They also cannot be
465 updated through the normal ref update machinery. Instead,
466 they are updated by directly writing to the files. However,
467 they can be read as if they were refs, so `git rev-parse
468 MERGE_HEAD` will work.
469
470 [[def_pull]]pull::
471 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
472 <<def_merge,merge>> it. See also linkgit:git-pull[1].
473
474 [[def_push]]push::
475 Pushing a <<def_branch,branch>> means to get the branch's
476 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>,
477 find out if it is an ancestor to the branch's local
478 head ref, and in that case, putting all
479 objects, which are <<def_reachable,reachable>> from the local
480 head ref, and which are missing from the remote
481 repository, into the remote
482 <<def_object_database,object database>>, and updating the remote
483 head ref. If the remote <<def_head,head>> is not an
484 ancestor to the local head, the push fails.
485
486 [[def_reachable]]reachable::
487 All of the ancestors of a given <<def_commit,commit>> are said to be
488 "reachable" from that commit. More
489 generally, one <<def_object,object>> is reachable from
490 another if we can reach the one from the other by a <<def_chain,chain>>
491 that follows <<def_tag,tags>> to whatever they tag,
492 <<def_commit_object,commits>> to their parents or trees, and
493 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>>
494 that they contain.
495
496 [[def_rebase]]rebase::
497 To reapply a series of changes from a <<def_branch,branch>> to a
498 different base, and reset the <<def_head,head>> of that branch
499 to the result.
500
501 [[def_ref]]ref::
502 A name that begins with `refs/` (e.g. `refs/heads/master`)
503 that points to an <<def_object_name,object name>> or another
504 ref (the latter is called a <<def_symref,symbolic ref>>).
505 For convenience, a ref can sometimes be abbreviated when used
506 as an argument to a Git command; see linkgit:gitrevisions[7]
507 for details.
508 Refs are stored in the <<def_repository,repository>>.
509 +
510 The ref namespace is hierarchical.
511 Different subhierarchies are used for different purposes (e.g. the
512 `refs/heads/` hierarchy is used to represent local branches).
513 +
514 There are a few special-purpose refs that do not begin with `refs/`.
515 The most notable example is `HEAD`.
516
517 [[def_reflog]]reflog::
518 A reflog shows the local "history" of a ref. In other words,
519 it can tell you what the 3rd last revision in _this_ repository
520 was, and what was the current state in _this_ repository,
521 yesterday 9:14pm. See linkgit:git-reflog[1] for details.
522
523 [[def_refspec]]refspec::
524 A "refspec" is used by <<def_fetch,fetch>> and
525 <<def_push,push>> to describe the mapping between remote
526 <<def_ref,ref>> and local ref.
527
528 [[def_remote]]remote repository::
529 A <<def_repository,repository>> which is used to track the same
530 project but resides somewhere else. To communicate with remotes,
531 see <<def_fetch,fetch>> or <<def_push,push>>.
532
533 [[def_remote_tracking_branch]]remote-tracking branch::
534 A <<def_ref,ref>> that is used to follow changes from another
535 <<def_repository,repository>>. It typically looks like
536 'refs/remotes/foo/bar' (indicating that it tracks a branch named
537 'bar' in a remote named 'foo'), and matches the right-hand-side of
538 a configured fetch <<def_refspec,refspec>>. A remote-tracking
539 branch should not contain direct modifications or have local
540 commits made to it.
541
542 [[def_repository]]repository::
543 A collection of <<def_ref,refs>> together with an
544 <<def_object_database,object database>> containing all objects
545 which are <<def_reachable,reachable>> from the refs, possibly
546 accompanied by meta data from one or more <<def_porcelain,porcelains>>. A
547 repository can share an object database with other repositories
548 via <<def_alternate_object_database,alternates mechanism>>.
549
550 [[def_resolve]]resolve::
551 The action of fixing up manually what a failed automatic
552 <<def_merge,merge>> left behind.
553
554 [[def_revision]]revision::
555 Synonym for <<def_commit,commit>> (the noun).
556
557 [[def_rewind]]rewind::
558 To throw away part of the development, i.e. to assign the
559 <<def_head,head>> to an earlier <<def_revision,revision>>.
560
561 [[def_SCM]]SCM::
562 Source code management (tool).
563
564 [[def_SHA1]]SHA-1::
565 "Secure Hash Algorithm 1"; a cryptographic hash function.
566 In the context of Git used as a synonym for <<def_object_name,object name>>.
567
568 [[def_shallow_clone]]shallow clone::
569 Mostly a synonym to <<def_shallow_repository,shallow repository>>
570 but the phrase makes it more explicit that it was created by
571 running `git clone --depth=...` command.
572
573 [[def_shallow_repository]]shallow repository::
574 A shallow <<def_repository,repository>> has an incomplete
575 history some of whose <<def_commit,commits>> have <<def_parent,parents>> cauterized away (in other
576 words, Git is told to pretend that these commits do not have the
577 parents, even though they are recorded in the <<def_commit_object,commit
578 object>>). This is sometimes useful when you are interested only in the
579 recent history of a project even though the real history recorded in the
580 upstream is much larger. A shallow repository
581 is created by giving the `--depth` option to linkgit:git-clone[1], and
582 its history can be later deepened with linkgit:git-fetch[1].
583
584 [[def_stash]]stash entry::
585 An <<def_object,object>> used to temporarily store the contents of a
586 <<def_dirty,dirty>> working directory and the index for future reuse.
587
588 [[def_submodule]]submodule::
589 A <<def_repository,repository>> that holds the history of a
590 separate project inside another repository (the latter of
591 which is called <<def_superproject, superproject>>).
592
593 [[def_superproject]]superproject::
594 A <<def_repository,repository>> that references repositories
595 of other projects in its working tree as <<def_submodule,submodules>>.
596 The superproject knows about the names of (but does not hold
597 copies of) commit objects of the contained submodules.
598
599 [[def_symref]]symref::
600 Symbolic reference: instead of containing the <<def_SHA1,SHA-1>>
601 id itself, it is of the format 'ref: refs/some/thing' and when
602 referenced, it recursively dereferences to this reference.
603 '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic
604 references are manipulated with the linkgit:git-symbolic-ref[1]
605 command.
606
607 [[def_tag]]tag::
608 A <<def_ref,ref>> under `refs/tags/` namespace that points to an
609 object of an arbitrary type (typically a tag points to either a
610 <<def_tag_object,tag>> or a <<def_commit_object,commit object>>).
611 In contrast to a <<def_head,head>>, a tag is not updated by
612 the `commit` command. A Git tag has nothing to do with a Lisp
613 tag (which would be called an <<def_object_type,object type>>
614 in Git's context). A tag is most typically used to mark a particular
615 point in the commit ancestry <<def_chain,chain>>.
616
617 [[def_tag_object]]tag object::
618 An <<def_object,object>> containing a <<def_ref,ref>> pointing to
619 another object, which can contain a message just like a
620 <<def_commit_object,commit object>>. It can also contain a (PGP)
621 signature, in which case it is called a "signed tag object".
622
623 [[def_topic_branch]]topic branch::
624 A regular Git <<def_branch,branch>> that is used by a developer to
625 identify a conceptual line of development. Since branches are very easy
626 and inexpensive, it is often desirable to have several small branches
627 that each contain very well defined concepts or small incremental yet
628 related changes.
629
630 [[def_tree]]tree::
631 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree
632 object>> together with the dependent <<def_blob_object,blob>> and tree objects
633 (i.e. a stored representation of a working tree).
634
635 [[def_tree_object]]tree object::
636 An <<def_object,object>> containing a list of file names and modes along
637 with refs to the associated blob and/or tree objects. A
638 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>.
639
640 [[def_tree-ish]]tree-ish (also treeish)::
641 A <<def_tree_object,tree object>> or an <<def_object,object>>
642 that can be recursively dereferenced to a tree object.
643 Dereferencing a <<def_commit_object,commit object>> yields the
644 tree object corresponding to the <<def_revision,revision>>'s
645 top <<def_directory,directory>>.
646 The following are all tree-ishes:
647 a <<def_commit-ish,commit-ish>>,
648 a tree object,
649 a <<def_tag_object,tag object>> that points to a tree object,
650 a tag object that points to a tag object that points to a tree
651 object,
652 etc.
653
654 [[def_unmerged_index]]unmerged index::
655 An <<def_index,index>> which contains unmerged
656 <<def_index_entry,index entries>>.
657
658 [[def_unreachable_object]]unreachable object::
659 An <<def_object,object>> which is not <<def_reachable,reachable>> from a
660 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference.
661
662 [[def_upstream_branch]]upstream branch::
663 The default <<def_branch,branch>> that is merged into the branch in
664 question (or the branch in question is rebased onto). It is configured
665 via branch.<name>.remote and branch.<name>.merge. If the upstream branch
666 of 'A' is 'origin/B' sometimes we say "'A' is tracking 'origin/B'".
667
668 [[def_working_tree]]working tree::
669 The tree of actual checked out files. The working tree normally
670 contains the contents of the <<def_HEAD,HEAD>> commit's tree,
671 plus any local changes that you have made but not yet committed.