1GITGLOSSARY(7) Git Manual GITGLOSSARY(7)
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6 gitglossary - A Git Glossary
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9 *
10
12 alternate object database
13 Via the alternates mechanism, a repository can inherit part of its
14 object database from another object database, which is called an
15 "alternate".
16 bare repository
18 A bare repository is normally an appropriately named directory with
19 a .git suffix that does not have a locally checked-out copy of any
20 of the files under revision control. That is, all of the Git
21 administrative and control files that would normally be present in
22 the hidden .git sub-directory are directly present in the
23 repository.git directory instead, and no other files are present
24 and checked out. Usually publishers of public repositories make
25 bare repositories available.
26 blob object
28 Untyped object, e.g. the contents of a file.
29 branch
31 A "branch" is an active line of development. The most recent commit
32 on a branch is referred to as the tip of that branch. The tip of
33 the branch is referenced by a branch head, which moves forward as
34 additional development is done on the branch. A single Git
35 repository can track an arbitrary number of branches, but your
36 working tree is associated with just one of them (the "current" or
37 "checked out" branch), and HEAD points to that branch.
38 cache
40 Obsolete for: index.
41 chain
43 A list of objects, where each object in the list contains a
44 reference to its successor (for example, the successor of a commit
45 could be one of its parents).
46 changeset
48 BitKeeper/cvsps speak for "commit". Since Git does not store
49 changes, but states, it really does not make sense to use the term
50 "changesets" with Git.
51 checkout
53 The action of updating all or part of the working tree with a tree
54 object or blob from the object database, and updating the index and
55 HEAD if the whole working tree has been pointed at a new branch.
56 cherry-picking
58 In SCM jargon, "cherry pick" means to choose a subset of changes
59 out of a series of changes (typically commits) and record them as a
60 new series of changes on top of a different codebase. In Git, this
61 is performed by the "git cherry-pick" command to extract the change
62 introduced by an existing commit and to record it based on the tip
63 of the current branch as a new commit.
64 clean
66 A working tree is clean, if it corresponds to the revision
67 referenced by the current head. Also see "dirty".
68 commit
70 As a noun: A single point in the Git history; the entire history of
71 a project is represented as a set of interrelated commits. The word
72 "commit" is often used by Git in the same places other revision
73 control systems use the words "revision" or "version". Also used as
74 a short hand for commit object.
75 As a verb: The action of storing a new snapshot of the project’s
77 state in the Git history, by creating a new commit representing the
78 current state of the index and advancing HEAD to point at the new
79 commit.
80 commit object
82 An object which contains the information about a particular
83 revision, such as parents, committer, author, date and the tree
84 object which corresponds to the top directory of the stored
85 revision.
86 commit-ish (also committish)
88 A commit object or an object that can be recursively dereferenced
89 to a commit object. The following are all commit-ishes: a commit
90 object, a tag object that points to a commit object, a tag object
91 that points to a tag object that points to a commit object, etc.
92 core Git
94 Fundamental data structures and utilities of Git. Exposes only
95 limited source code management tools.
96 DAG
98 Directed acyclic graph. The commit objects form a directed acyclic
99 graph, because they have parents (directed), and the graph of
100 commit objects is acyclic (there is no chain which begins and ends
101 with the same object).
102 dangling object
104 An unreachable object which is not reachable even from other
105 unreachable objects; a dangling object has no references to it from
106 any reference or object in the repository.
107 detached HEAD
109 Normally the HEAD stores the name of a branch, and commands that
110 operate on the history HEAD represents operate on the history
111 leading to the tip of the branch the HEAD points at. However, Git
112 also allows you to check out an arbitrary commit that isn’t
113 necessarily the tip of any particular branch. The HEAD in such a
114 state is called "detached".
115 Note that commands that operate on the history of the current
117 branch (e.g. git commit to build a new history on top of it) still
118 work while the HEAD is detached. They update the HEAD to point at
119 the tip of the updated history without affecting any branch.
120 Commands that update or inquire information about the current
121 branch (e.g. git branch --set-upstream-to that sets what
122 remote-tracking branch the current branch integrates with)
123 obviously do not work, as there is no (real) current branch to ask
124 about in this state.
125 directory
127 The list you get with "ls" :-)
128 dirty
130 A working tree is said to be "dirty" if it contains modifications
131 which have not been committed to the current branch.
132 evil merge
134 An evil merge is a merge that introduces changes that do not appear
135 in any parent.
136 fast-forward
138 A fast-forward is a special type of merge where you have a revision
139 and you are "merging" another branch's changes that happen to be a
140 descendant of what you have. In such a case, you do not make a new
141 merge commit but instead just update to his revision. This will
142 happen frequently on a remote-tracking branch of a remote
143 repository.
144 fetch
146 Fetching a branch means to get the branch’s head ref from a remote
147 repository, to find out which objects are missing from the local
148 object database, and to get them, too. See also git-fetch(1).
149 file system
151 Linus Torvalds originally designed Git to be a user space file
152 system, i.e. the infrastructure to hold files and directories. That
153 ensured the efficiency and speed of Git.
154 Git archive
156 Synonym for repository (for arch people).
157 gitfile
159 A plain file .git at the root of a working tree that points at the
160 directory that is the real repository.
161 grafts
163 Grafts enables two otherwise different lines of development to be
164 joined together by recording fake ancestry information for commits.
165 This way you can make Git pretend the set of parents a commit has
166 is different from what was recorded when the commit was created.
167 Configured via the .git/info/grafts file.
168 Note that the grafts mechanism is outdated and can lead to problems
170 transferring objects between repositories; see git-replace(1) for a
171 more flexible and robust system to do the same thing.
172 hash
174 In Git’s context, synonym for object name.
175 head
177 A named reference to the commit at the tip of a branch. Heads are
178 stored in a file in $GIT_DIR/refs/heads/ directory, except when
179 using packed refs. (See git-pack-refs(1).)
180 HEAD
182 The current branch. In more detail: Your working tree is normally
183 derived from the state of the tree referred to by HEAD. HEAD is a
184 reference to one of the heads in your repository, except when using
185 a detached HEAD, in which case it directly references an arbitrary
186 commit.
187 head ref
189 A synonym for head.
190 hook
192 During the normal execution of several Git commands, call-outs are
193 made to optional scripts that allow a developer to add
194 functionality or checking. Typically, the hooks allow for a command
195 to be pre-verified and potentially aborted, and allow for a
196 post-notification after the operation is done. The hook scripts are
197 found in the $GIT_DIR/hooks/ directory, and are enabled by simply
198 removing the .sample suffix from the filename. In earlier versions
199 of Git you had to make them executable.
200 index
202 A collection of files with stat information, whose contents are
203 stored as objects. The index is a stored version of your working
204 tree. Truth be told, it can also contain a second, and even a third
205 version of a working tree, which are used when merging.
206 index entry
208 The information regarding a particular file, stored in the index.
209 An index entry can be unmerged, if a merge was started, but not yet
210 finished (i.e. if the index contains multiple versions of that
211 file).
212 master
214 The default development branch. Whenever you create a Git
215 repository, a branch named "master" is created, and becomes the
216 active branch. In most cases, this contains the local development,
217 though that is purely by convention and is not required.
218 merge
220 As a verb: To bring the contents of another branch (possibly from
221 an external repository) into the current branch. In the case where
222 the merged-in branch is from a different repository, this is done
223 by first fetching the remote branch and then merging the result
224 into the current branch. This combination of fetch and merge
225 operations is called a pull. Merging is performed by an automatic
226 process that identifies changes made since the branches diverged,
227 and then applies all those changes together. In cases where changes
228 conflict, manual intervention may be required to complete the
229 merge.
230 As a noun: unless it is a fast-forward, a successful merge results
232 in the creation of a new commit representing the result of the
233 merge, and having as parents the tips of the merged branches. This
234 commit is referred to as a "merge commit", or sometimes just a
235 "merge".
236 object
238 The unit of storage in Git. It is uniquely identified by the SHA-1
239 of its contents. Consequently, an object cannot be changed.
240 object database
242 Stores a set of "objects", and an individual object is identified
243 by its object name. The objects usually live in $GIT_DIR/objects/.
244 object identifier
246 Synonym for object name.
247 object name
249 The unique identifier of an object. The object name is usually
250 represented by a 40 character hexadecimal string. Also colloquially
251 called SHA-1.
252 object type
254 One of the identifiers "commit", "tree", "tag" or "blob" describing
255 the type of an object.
256 octopus
258 To merge more than two branches.
259 origin
261 The default upstream repository. Most projects have at least one
262 upstream project which they track. By default origin is used for
263 that purpose. New upstream updates will be fetched into
264 remote-tracking branches named origin/name-of-upstream-branch,
265 which you can see using git branch -r.
266 overlay
268 Only update and add files to the working directory, but don’t
269 delete them, similar to how cp -R would update the contents in the
270 destination directory. This is the default mode in a checkout when
271 checking out files from the index or a tree-ish. In contrast,
272 no-overlay mode also deletes tracked files not present in the
273 source, similar to rsync --delete.
274 pack
276 A set of objects which have been compressed into one file (to save
277 space or to transmit them efficiently).
278 pack index
280 The list of identifiers, and other information, of the objects in a
281 pack, to assist in efficiently accessing the contents of a pack.
282 pathspec
284 Pattern used to limit paths in Git commands.
285 Pathspecs are used on the command line of "git ls-files", "git
287 ls-tree", "git add", "git grep", "git diff", "git checkout", and
288 many other commands to limit the scope of operations to some subset
289 of the tree or worktree. See the documentation of each command for
290 whether paths are relative to the current directory or toplevel.
291 The pathspec syntax is as follows:
292 · any path matches itself
294 · the pathspec up to the last slash represents a directory
296 prefix. The scope of that pathspec is limited to that subtree.
297 · the rest of the pathspec is a pattern for the remainder of the
299 pathname. Paths relative to the directory prefix will be
300 matched against that pattern using fnmatch(3); in particular, *
301 and ? can match directory separators.
302 For example, Documentation/*.jpg will match all .jpg files in the
304 Documentation subtree, including
305 Documentation/chapter_1/figure_1.jpg.
306 A pathspec that begins with a colon : has special meaning. In the
308 short form, the leading colon : is followed by zero or more "magic
309 signature" letters (which optionally is terminated by another colon
310 :), and the remainder is the pattern to match against the path. The
311 "magic signature" consists of ASCII symbols that are neither
312 alphanumeric, glob, regex special characters nor colon. The
313 optional colon that terminates the "magic signature" can be omitted
314 if the pattern begins with a character that does not belong to
315 "magic signature" symbol set and is not a colon.
316 In the long form, the leading colon : is followed by an open
318 parenthesis (, a comma-separated list of zero or more "magic
319 words", and a close parentheses ), and the remainder is the pattern
320 to match against the path.
321 A pathspec with only a colon means "there is no pathspec". This
323 form should not be combined with other pathspec.
324 top
326 The magic word top (magic signature: /) makes the pattern match
327 from the root of the working tree, even when you are running
328 the command from inside a subdirectory.
329 literal
331 Wildcards in the pattern such as * or ? are treated as literal
332 characters.
333 icase
335 Case insensitive match.
336 glob
338 Git treats the pattern as a shell glob suitable for consumption
339 by fnmatch(3) with the FNM_PATHNAME flag: wildcards in the
340 pattern will not match a / in the pathname. For example,
341 "Documentation/*.html" matches "Documentation/git.html" but not
342 "Documentation/ppc/ppc.html" or
343 "tools/perf/Documentation/perf.html".
344 Two consecutive asterisks ("**") in patterns matched against
346 full pathname may have special meaning:
347 · A leading "**" followed by a slash means match in all
349 directories. For example, "**/foo" matches file or
350 directory "foo" anywhere, the same as pattern "foo".
351 "**/foo/bar" matches file or directory "bar" anywhere that
352 is directly under directory "foo".
353 · A trailing "/**" matches everything inside. For example,
355 "abc/**" matches all files inside directory "abc", relative
356 to the location of the .gitignore file, with infinite
357 depth.
358 · A slash followed by two consecutive asterisks then a slash
360 matches zero or more directories. For example, "a/**/b"
361 matches "a/b", "a/x/b", "a/x/y/b" and so on.
362 · Other consecutive asterisks are considered invalid.
364 Glob magic is incompatible with literal magic.
366 attr
368 After attr: comes a space separated list of "attribute
369 requirements", all of which must be met in order for the path
370 to be considered a match; this is in addition to the usual
371 non-magic pathspec pattern matching. See gitattributes(5).
372 Each of the attribute requirements for the path takes one of
374 these forms:
375 · "ATTR" requires that the attribute ATTR be set.
377 · "-ATTR" requires that the attribute ATTR be unset.
379 · "ATTR=VALUE" requires that the attribute ATTR be set to the
381 string VALUE.
382 · "!ATTR" requires that the attribute ATTR be unspecified.
384 Note that when matching against a tree object, attributes
386 are still obtained from working tree, not from the given
387 tree object.
388 exclude
390 After a path matches any non-exclude pathspec, it will be run
391 through all exclude pathspecs (magic signature: ! or its
392 synonym ^). If it matches, the path is ignored. When there is
393 no non-exclude pathspec, the exclusion is applied to the result
394 set as if invoked without any pathspec.
395 parent
397 A commit object contains a (possibly empty) list of the logical
398 predecessor(s) in the line of development, i.e. its parents.
399 pickaxe
401 The term pickaxe refers to an option to the diffcore routines that
402 help select changes that add or delete a given text string. With
403 the --pickaxe-all option, it can be used to view the full changeset
404 that introduced or removed, say, a particular line of text. See
405 git-diff(1).
406 plumbing
408 Cute name for core Git.
409 porcelain
411 Cute name for programs and program suites depending on core Git,
412 presenting a high level access to core Git. Porcelains expose more
413 of a SCM interface than the plumbing.
414 per-worktree ref
416 Refs that are per-worktree, rather than global. This is presently
417 only HEAD and any refs that start with refs/bisect/, but might
418 later include other unusual refs.
419 pseudoref
421 Pseudorefs are a class of files under $GIT_DIR which behave like
422 refs for the purposes of rev-parse, but which are treated specially
423 by git. Pseudorefs both have names that are all-caps, and always
424 start with a line consisting of a SHA-1 followed by whitespace. So,
425 HEAD is not a pseudoref, because it is sometimes a symbolic ref.
426 They might optionally contain some additional data. MERGE_HEAD and
427 CHERRY_PICK_HEAD are examples. Unlike per-worktree refs, these
428 files cannot be symbolic refs, and never have reflogs. They also
429 cannot be updated through the normal ref update machinery. Instead,
430 they are updated by directly writing to the files. However, they
431 can be read as if they were refs, so git rev-parse MERGE_HEAD will
432 work.
433 pull
435 Pulling a branch means to fetch it and merge it. See also git-
436 pull(1).
437 push
439 Pushing a branch means to get the branch’s head ref from a remote
440 repository, find out if it is an ancestor to the branch’s local
441 head ref, and in that case, putting all objects, which are
442 reachable from the local head ref, and which are missing from the
443 remote repository, into the remote object database, and updating
444 the remote head ref. If the remote head is not an ancestor to the
445 local head, the push fails.
446 reachable
448 All of the ancestors of a given commit are said to be "reachable"
449 from that commit. More generally, one object is reachable from
450 another if we can reach the one from the other by a chain that
451 follows tags to whatever they tag, commits to their parents or
452 trees, and trees to the trees or blobs that they contain.
453 rebase
455 To reapply a series of changes from a branch to a different base,
456 and reset the head of that branch to the result.
457 ref
459 A name that begins with refs/ (e.g. refs/heads/master) that points
460 to an object name or another ref (the latter is called a symbolic
461 ref). For convenience, a ref can sometimes be abbreviated when used
462 as an argument to a Git command; see gitrevisions(7) for details.
463 Refs are stored in the repository.
464 The ref namespace is hierarchical. Different subhierarchies are
466 used for different purposes (e.g. the refs/heads/ hierarchy is used
467 to represent local branches).
468 There are a few special-purpose refs that do not begin with refs/.
470 The most notable example is HEAD.
471 reflog
473 A reflog shows the local "history" of a ref. In other words, it can
474 tell you what the 3rd last revision in this repository was, and
475 what was the current state in this repository, yesterday 9:14pm.
476 See git-reflog(1) for details.
477 refspec
479 A "refspec" is used by fetch and push to describe the mapping
480 between remote ref and local ref.
481 remote repository
483 A repository which is used to track the same project but resides
484 somewhere else. To communicate with remotes, see fetch or push.
485 remote-tracking branch
487 A ref that is used to follow changes from another repository. It
488 typically looks like refs/remotes/foo/bar (indicating that it
489 tracks a branch named bar in a remote named foo), and matches the
490 right-hand-side of a configured fetch refspec. A remote-tracking
491 branch should not contain direct modifications or have local
492 commits made to it.
493 repository
495 A collection of refs together with an object database containing
496 all objects which are reachable from the refs, possibly accompanied
497 by meta data from one or more porcelains. A repository can share an
498 object database with other repositories via alternates mechanism.
499 resolve
501 The action of fixing up manually what a failed automatic merge left
502 behind.
503 revision
505 Synonym for commit (the noun).
506 rewind
508 To throw away part of the development, i.e. to assign the head to
509 an earlier revision.
510 SCM
512 Source code management (tool).
513 SHA-1
515 "Secure Hash Algorithm 1"; a cryptographic hash function. In the
516 context of Git used as a synonym for object name.
517 shallow clone
519 Mostly a synonym to shallow repository but the phrase makes it more
520 explicit that it was created by running git clone --depth=...
521 command.
522 shallow repository
524 A shallow repository has an incomplete history some of whose
525 commits have parents cauterized away (in other words, Git is told
526 to pretend that these commits do not have the parents, even though
527 they are recorded in the commit object). This is sometimes useful
528 when you are interested only in the recent history of a project
529 even though the real history recorded in the upstream is much
530 larger. A shallow repository is created by giving the --depth
531 option to git-clone(1), and its history can be later deepened with
532 git-fetch(1).
533 stash entry
535 An object used to temporarily store the contents of a dirty working
536 directory and the index for future reuse.
537 submodule
539 A repository that holds the history of a separate project inside
540 another repository (the latter of which is called superproject).
541 superproject
543 A repository that references repositories of other projects in its
544 working tree as submodules. The superproject knows about the names
545 of (but does not hold copies of) commit objects of the contained
546 submodules.
547 symref
549 Symbolic reference: instead of containing the SHA-1 id itself, it
550 is of the format ref: refs/some/thing and when referenced, it
551 recursively dereferences to this reference. HEAD is a prime
552 example of a symref. Symbolic references are manipulated with the
553 git-symbolic-ref(1) command.
554 tag
556 A ref under refs/tags/ namespace that points to an object of an
557 arbitrary type (typically a tag points to either a tag or a commit
558 object). In contrast to a head, a tag is not updated by the commit
559 command. A Git tag has nothing to do with a Lisp tag (which would
560 be called an object type in Git’s context). A tag is most typically
561 used to mark a particular point in the commit ancestry chain.
562 tag object
564 An object containing a ref pointing to another object, which can
565 contain a message just like a commit object. It can also contain a
566 (PGP) signature, in which case it is called a "signed tag object".
567 topic branch
569 A regular Git branch that is used by a developer to identify a
570 conceptual line of development. Since branches are very easy and
571 inexpensive, it is often desirable to have several small branches
572 that each contain very well defined concepts or small incremental
573 yet related changes.
574 tree
576 Either a working tree, or a tree object together with the dependent
577 blob and tree objects (i.e. a stored representation of a working
578 tree).
579 tree object
581 An object containing a list of file names and modes along with refs
582 to the associated blob and/or tree objects. A tree is equivalent to
583 a directory.
584 tree-ish (also treeish)
586 A tree object or an object that can be recursively dereferenced to
587 a tree object. Dereferencing a commit object yields the tree object
588 corresponding to the revision's top directory. The following are
589 all tree-ishes: a commit-ish, a tree object, a tag object that
590 points to a tree object, a tag object that points to a tag object
591 that points to a tree object, etc.
592 unmerged index
594 An index which contains unmerged index entries.
595 unreachable object
597 An object which is not reachable from a branch, tag, or any other
598 reference.
599 upstream branch
601 The default branch that is merged into the branch in question (or
602 the branch in question is rebased onto). It is configured via
603 branch.<name>.remote and branch.<name>.merge. If the upstream
604 branch of A is origin/B sometimes we say "A is tracking origin/B".
605 working tree
607 The tree of actual checked out files. The working tree normally
608 contains the contents of the HEAD commit’s tree, plus any local
609 changes that you have made but not yet committed.
610
612 gittutorial(7), gittutorial-2(7), gitcvs-migration(7), giteveryday(7),
613 The Git User’s Manual[1]
614
616 Part of the git(1) suite
617
619 1. The Git User’s Manual
620 file:///usr/share/doc/git/user-manual.html
621Git 2.24.1 12/10/2019 GITGLOSSARY(7)