1GITGLOSSARY(7) Git Manual GITGLOSSARY(7)
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6 gitglossary - A Git Glossary
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9 *
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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 a line of development. The most recent commit on a
32 branch is referred to as the tip of that branch. The tip of the
33 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 graph concept, representations and usage
82 A synonym for the DAG structure formed by the commits in the object
83 database, referenced by branch tips, using their chain of linked
84 commits. This structure is the definitive commit graph. The graph
85 can be represented in other ways, e.g. the "commit-graph" file.
86 commit-graph file
88 The "commit-graph" (normally hyphenated) file is a supplemental
89 representation of the commit graph which accelerates commit graph
90 walks. The "commit-graph" file is stored either in the
91 .git/objects/info directory or in the info directory of an
92 alternate object database.
93 commit object
95 An object which contains the information about a particular
96 revision, such as parents, committer, author, date and the tree
97 object which corresponds to the top directory of the stored
98 revision.
99 commit-ish (also committish)
101 A commit object or an object that can be recursively dereferenced
102 to a commit object. The following are all commit-ishes: a commit
103 object, a tag object that points to a commit object, a tag object
104 that points to a tag object that points to a commit object, etc.
105 core Git
107 Fundamental data structures and utilities of Git. Exposes only
108 limited source code management tools.
109 DAG
111 Directed acyclic graph. The commit objects form a directed acyclic
112 graph, because they have parents (directed), and the graph of
113 commit objects is acyclic (there is no chain which begins and ends
114 with the same object).
115 dangling object
117 An unreachable object which is not reachable even from other
118 unreachable objects; a dangling object has no references to it from
119 any reference or object in the repository.
120 detached HEAD
122 Normally the HEAD stores the name of a branch, and commands that
123 operate on the history HEAD represents operate on the history
124 leading to the tip of the branch the HEAD points at. However, Git
125 also allows you to check out an arbitrary commit that isn’t
126 necessarily the tip of any particular branch. The HEAD in such a
127 state is called "detached".
128 Note that commands that operate on the history of the current
130 branch (e.g. git commit to build a new history on top of it) still
131 work while the HEAD is detached. They update the HEAD to point at
132 the tip of the updated history without affecting any branch.
133 Commands that update or inquire information about the current
134 branch (e.g. git branch --set-upstream-to that sets what
135 remote-tracking branch the current branch integrates with)
136 obviously do not work, as there is no (real) current branch to ask
137 about in this state.
138 directory
140 The list you get with "ls" :-)
141 dirty
143 A working tree is said to be "dirty" if it contains modifications
144 which have not been committed to the current branch.
145 evil merge
147 An evil merge is a merge that introduces changes that do not appear
148 in any parent.
149 fast-forward
151 A fast-forward is a special type of merge where you have a revision
152 and you are "merging" another branch's changes that happen to be a
153 descendant of what you have. In such a case, you do not make a new
154 merge commit but instead just update your branch to point at the
155 same revision as the branch you are merging. This will happen
156 frequently on a remote-tracking branch of a remote repository.
157 fetch
159 Fetching a branch means to get the branch’s head ref from a remote
160 repository, to find out which objects are missing from the local
161 object database, and to get them, too. See also git-fetch(1).
162 file system
164 Linus Torvalds originally designed Git to be a user space file
165 system, i.e. the infrastructure to hold files and directories. That
166 ensured the efficiency and speed of Git.
167 Git archive
169 Synonym for repository (for arch people).
170 gitfile
172 A plain file .git at the root of a working tree that points at the
173 directory that is the real repository.
174 grafts
176 Grafts enables two otherwise different lines of development to be
177 joined together by recording fake ancestry information for commits.
178 This way you can make Git pretend the set of parents a commit has
179 is different from what was recorded when the commit was created.
180 Configured via the .git/info/grafts file.
181 Note that the grafts mechanism is outdated and can lead to problems
183 transferring objects between repositories; see git-replace(1) for a
184 more flexible and robust system to do the same thing.
185 hash
187 In Git’s context, synonym for object name.
188 head
190 A named reference to the commit at the tip of a branch. Heads are
191 stored in a file in $GIT_DIR/refs/heads/ directory, except when
192 using packed refs. (See git-pack-refs(1).)
193 HEAD
195 The current branch. In more detail: Your working tree is normally
196 derived from the state of the tree referred to by HEAD. HEAD is a
197 reference to one of the heads in your repository, except when using
198 a detached HEAD, in which case it directly references an arbitrary
199 commit.
200 head ref
202 A synonym for head.
203 hook
205 During the normal execution of several Git commands, call-outs are
206 made to optional scripts that allow a developer to add
207 functionality or checking. Typically, the hooks allow for a command
208 to be pre-verified and potentially aborted, and allow for a
209 post-notification after the operation is done. The hook scripts are
210 found in the $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 index
215 A collection of files with stat information, whose contents are
216 stored as objects. The index is a stored version of your working
217 tree. Truth be told, it can also contain a second, and even a third
218 version of a working tree, which are used when merging.
219 index entry
221 The information regarding a particular file, stored in the index.
222 An index entry can be unmerged, if a merge was started, but not yet
223 finished (i.e. if the index contains multiple versions of that
224 file).
225 master
227 The default development branch. Whenever you create a Git
228 repository, a branch named "master" is created, and becomes the
229 active branch. In most cases, this contains the local development,
230 though that is purely by convention and is not required.
231 merge
233 As a verb: To bring the contents of another branch (possibly from
234 an external repository) into the current branch. In the case where
235 the merged-in branch is from a different repository, this is done
236 by first fetching the remote branch and then merging the result
237 into the current branch. This combination of fetch and merge
238 operations is called a pull. Merging is performed by an automatic
239 process that identifies changes made since the branches diverged,
240 and then applies all those changes together. In cases where changes
241 conflict, manual intervention may be required to complete the
242 merge.
243 As a noun: unless it is a fast-forward, a successful merge results
245 in the creation of a new commit representing the result of the
246 merge, and having as parents the tips of the merged branches. This
247 commit is referred to as a "merge commit", or sometimes just a
248 "merge".
249 object
251 The unit of storage in Git. It is uniquely identified by the SHA-1
252 of its contents. Consequently, an object cannot be changed.
253 object database
255 Stores a set of "objects", and an individual object is identified
256 by its object name. The objects usually live in $GIT_DIR/objects/.
257 object identifier (oid)
259 Synonym for object name.
260 object name
262 The unique identifier of an object. The object name is usually
263 represented by a 40 character hexadecimal string. Also colloquially
264 called SHA-1.
265 object type
267 One of the identifiers "commit", "tree", "tag" or "blob" describing
268 the type of an object.
269 octopus
271 To merge more than two branches.
272 origin
274 The default upstream repository. Most projects have at least one
275 upstream project which they track. By default origin is used for
276 that purpose. New upstream updates will be fetched into
277 remote-tracking branches named origin/name-of-upstream-branch,
278 which you can see using git branch -r.
279 overlay
281 Only update and add files to the working directory, but don’t
282 delete them, similar to how cp -R would update the contents in the
283 destination directory. This is the default mode in a checkout when
284 checking out files from the index or a tree-ish. In contrast,
285 no-overlay mode also deletes tracked files not present in the
286 source, similar to rsync --delete.
287 pack
289 A set of objects which have been compressed into one file (to save
290 space or to transmit them efficiently).
291 pack index
293 The list of identifiers, and other information, of the objects in a
294 pack, to assist in efficiently accessing the contents of a pack.
295 pathspec
297 Pattern used to limit paths in Git commands.
298 Pathspecs are used on the command line of "git ls-files", "git
300 ls-tree", "git add", "git grep", "git diff", "git checkout", and
301 many other commands to limit the scope of operations to some subset
302 of the tree or working tree. See the documentation of each command
303 for whether paths are relative to the current directory or
304 toplevel. The pathspec syntax is as follows:
305 • any path matches itself
307 • the pathspec up to the last slash represents a directory
309 prefix. The scope of that pathspec is limited to that subtree.
310 • the rest of the pathspec is a pattern for the remainder of the
312 pathname. Paths relative to the directory prefix will be
313 matched against that pattern using fnmatch(3); in particular, *
314 and ? can match directory separators.
315 For example, Documentation/*.jpg will match all .jpg files in the
317 Documentation subtree, including
318 Documentation/chapter_1/figure_1.jpg.
319 A pathspec that begins with a colon : has special meaning. In the
321 short form, the leading colon : is followed by zero or more "magic
322 signature" letters (which optionally is terminated by another colon
323 :), and the remainder is the pattern to match against the path. The
324 "magic signature" consists of ASCII symbols that are neither
325 alphanumeric, glob, regex special characters nor colon. The
326 optional colon that terminates the "magic signature" can be omitted
327 if the pattern begins with a character that does not belong to
328 "magic signature" symbol set and is not a colon.
329 In the long form, the leading colon : is followed by an open
331 parenthesis (, a comma-separated list of zero or more "magic
332 words", and a close parentheses ), and the remainder is the pattern
333 to match against the path.
334 A pathspec with only a colon means "there is no pathspec". This
336 form should not be combined with other pathspec.
337 top
339 The magic word top (magic signature: /) makes the pattern match
340 from the root of the working tree, even when you are running
341 the command from inside a subdirectory.
342 literal
344 Wildcards in the pattern such as * or ? are treated as literal
345 characters.
346 icase
348 Case insensitive match.
349 glob
351 Git treats the pattern as a shell glob suitable for consumption
352 by fnmatch(3) with the FNM_PATHNAME flag: wildcards in the
353 pattern will not match a / in the pathname. For example,
354 "Documentation/*.html" matches "Documentation/git.html" but not
355 "Documentation/ppc/ppc.html" or
356 "tools/perf/Documentation/perf.html".
357 Two consecutive asterisks ("**") in patterns matched against
359 full pathname may have special meaning:
360 • A leading "**" followed by a slash means match in all
362 directories. For example, "**/foo" matches file or
363 directory "foo" anywhere, the same as pattern "foo".
364 "**/foo/bar" matches file or directory "bar" anywhere that
365 is directly under directory "foo".
366 • A trailing "/**" matches everything inside. For example,
368 "abc/**" matches all files inside directory "abc", relative
369 to the location of the .gitignore file, with infinite
370 depth.
371 • A slash followed by two consecutive asterisks then a slash
373 matches zero or more directories. For example, "a/**/b"
374 matches "a/b", "a/x/b", "a/x/y/b" and so on.
375 • Other consecutive asterisks are considered invalid.
377 Glob magic is incompatible with literal magic.
379 attr
381 After attr: comes a space separated list of "attribute
382 requirements", all of which must be met in order for the path
383 to be considered a match; this is in addition to the usual
384 non-magic pathspec pattern matching. See gitattributes(5).
385 Each of the attribute requirements for the path takes one of
387 these forms:
388 • "ATTR" requires that the attribute ATTR be set.
390 • "-ATTR" requires that the attribute ATTR be unset.
392 • "ATTR=VALUE" requires that the attribute ATTR be set to the
394 string VALUE.
395 • "!ATTR" requires that the attribute ATTR be unspecified.
397 Note that when matching against a tree object, attributes
399 are still obtained from working tree, not from the given
400 tree object.
401 exclude
403 After a path matches any non-exclude pathspec, it will be run
404 through all exclude pathspecs (magic signature: ! or its
405 synonym ^). If it matches, the path is ignored. When there is
406 no non-exclude pathspec, the exclusion is applied to the result
407 set as if invoked without any pathspec.
408 parent
410 A commit object contains a (possibly empty) list of the logical
411 predecessor(s) in the line of development, i.e. its parents.
412 pickaxe
414 The term pickaxe refers to an option to the diffcore routines that
415 help select changes that add or delete a given text string. With
416 the --pickaxe-all option, it can be used to view the full changeset
417 that introduced or removed, say, a particular line of text. See
418 git-diff(1).
419 plumbing
421 Cute name for core Git.
422 porcelain
424 Cute name for programs and program suites depending on core Git,
425 presenting a high level access to core Git. Porcelains expose more
426 of a SCM interface than the plumbing.
427 per-worktree ref
429 Refs that are per-worktree, rather than global. This is presently
430 only HEAD and any refs that start with refs/bisect/, but might
431 later include other unusual refs.
432 pseudoref
434 Pseudorefs are a class of files under $GIT_DIR which behave like
435 refs for the purposes of rev-parse, but which are treated specially
436 by git. Pseudorefs both have names that are all-caps, and always
437 start with a line consisting of a SHA-1 followed by whitespace. So,
438 HEAD is not a pseudoref, because it is sometimes a symbolic ref.
439 They might optionally contain some additional data. MERGE_HEAD and
440 CHERRY_PICK_HEAD are examples. Unlike per-worktree refs, these
441 files cannot be symbolic refs, and never have reflogs. They also
442 cannot be updated through the normal ref update machinery. Instead,
443 they are updated by directly writing to the files. However, they
444 can be read as if they were refs, so git rev-parse MERGE_HEAD will
445 work.
446 pull
448 Pulling a branch means to fetch it and merge it. See also git-
449 pull(1).
450 push
452 Pushing a branch means to get the branch’s head ref from a remote
453 repository, find out if it is an ancestor to the branch’s local
454 head ref, and in that case, putting all objects, which are
455 reachable from the local head ref, and which are missing from the
456 remote repository, into the remote object database, and updating
457 the remote head ref. If the remote head is not an ancestor to the
458 local head, the push fails.
459 reachable
461 All of the ancestors of a given commit are said to be "reachable"
462 from that commit. More generally, one object is reachable from
463 another if we can reach the one from the other by a chain that
464 follows tags to whatever they tag, commits to their parents or
465 trees, and trees to the trees or blobs that they contain.
466 reachability bitmaps
468 Reachability bitmaps store information about the reachability of a
469 selected set of commits in a packfile, or a multi-pack index
470 (MIDX), to speed up object search. The bitmaps are stored in a
471 ".bitmap" file. A repository may have at most one bitmap file in
472 use. The bitmap file may belong to either one pack, or the
473 repository’s multi-pack index (if it exists).
474 rebase
476 To reapply a series of changes from a branch to a different base,
477 and reset the head of that branch to the result.
478 ref
480 A name that begins with refs/ (e.g. refs/heads/master) that points
481 to an object name or another ref (the latter is called a symbolic
482 ref). For convenience, a ref can sometimes be abbreviated when used
483 as an argument to a Git command; see gitrevisions(7) for details.
484 Refs are stored in the repository.
485 The ref namespace is hierarchical. Different subhierarchies are
487 used for different purposes (e.g. the refs/heads/ hierarchy is used
488 to represent local branches).
489 There are a few special-purpose refs that do not begin with refs/.
491 The most notable example is HEAD.
492 reflog
494 A reflog shows the local "history" of a ref. In other words, it can
495 tell you what the 3rd last revision in this repository was, and
496 what was the current state in this repository, yesterday 9:14pm.
497 See git-reflog(1) for details.
498 refspec
500 A "refspec" is used by fetch and push to describe the mapping
501 between remote ref and local ref.
502 remote repository
504 A repository which is used to track the same project but resides
505 somewhere else. To communicate with remotes, see fetch or push.
506 remote-tracking branch
508 A ref that is used to follow changes from another repository. It
509 typically looks like refs/remotes/foo/bar (indicating that it
510 tracks a branch named bar in a remote named foo), and matches the
511 right-hand-side of a configured fetch refspec. A remote-tracking
512 branch should not contain direct modifications or have local
513 commits made to it.
514 repository
516 A collection of refs together with an object database containing
517 all objects which are reachable from the refs, possibly accompanied
518 by meta data from one or more porcelains. A repository can share an
519 object database with other repositories via alternates mechanism.
520 resolve
522 The action of fixing up manually what a failed automatic merge left
523 behind.
524 revision
526 Synonym for commit (the noun).
527 rewind
529 To throw away part of the development, i.e. to assign the head to
530 an earlier revision.
531 SCM
533 Source code management (tool).
534 SHA-1
536 "Secure Hash Algorithm 1"; a cryptographic hash function. In the
537 context of Git used as a synonym for object name.
538 shallow clone
540 Mostly a synonym to shallow repository but the phrase makes it more
541 explicit that it was created by running git clone --depth=...
542 command.
543 shallow repository
545 A shallow repository has an incomplete history some of whose
546 commits have parents cauterized away (in other words, Git is told
547 to pretend that these commits do not have the parents, even though
548 they are recorded in the commit object). This is sometimes useful
549 when you are interested only in the recent history of a project
550 even though the real history recorded in the upstream is much
551 larger. A shallow repository is created by giving the --depth
552 option to git-clone(1), and its history can be later deepened with
553 git-fetch(1).
554 stash entry
556 An object used to temporarily store the contents of a dirty working
557 directory and the index for future reuse.
558 submodule
560 A repository that holds the history of a separate project inside
561 another repository (the latter of which is called superproject).
562 superproject
564 A repository that references repositories of other projects in its
565 working tree as submodules. The superproject knows about the names
566 of (but does not hold copies of) commit objects of the contained
567 submodules.
568 symref
570 Symbolic reference: instead of containing the SHA-1 id itself, it
571 is of the format ref: refs/some/thing and when referenced, it
572 recursively dereferences to this reference. HEAD is a prime
573 example of a symref. Symbolic references are manipulated with the
574 git-symbolic-ref(1) command.
575 tag
577 A ref under refs/tags/ namespace that points to an object of an
578 arbitrary type (typically a tag points to either a tag or a commit
579 object). In contrast to a head, a tag is not updated by the commit
580 command. A Git tag has nothing to do with a Lisp tag (which would
581 be called an object type in Git’s context). A tag is most typically
582 used to mark a particular point in the commit ancestry chain.
583 tag object
585 An object containing a ref pointing to another object, which can
586 contain a message just like a commit object. It can also contain a
587 (PGP) signature, in which case it is called a "signed tag object".
588 topic branch
590 A regular Git branch that is used by a developer to identify a
591 conceptual line of development. Since branches are very easy and
592 inexpensive, it is often desirable to have several small branches
593 that each contain very well defined concepts or small incremental
594 yet related changes.
595 tree
597 Either a working tree, or a tree object together with the dependent
598 blob and tree objects (i.e. a stored representation of a working
599 tree).
600 tree object
602 An object containing a list of file names and modes along with refs
603 to the associated blob and/or tree objects. A tree is equivalent to
604 a directory.
605 tree-ish (also treeish)
607 A tree object or an object that can be recursively dereferenced to
608 a tree object. Dereferencing a commit object yields the tree object
609 corresponding to the revision's top directory. The following are
610 all tree-ishes: a commit-ish, a tree object, a tag object that
611 points to a tree object, a tag object that points to a tag object
612 that points to a tree object, etc.
613 unmerged index
615 An index which contains unmerged index entries.
616 unreachable object
618 An object which is not reachable from a branch, tag, or any other
619 reference.
620 upstream branch
622 The default branch that is merged into the branch in question (or
623 the branch in question is rebased onto). It is configured via
624 branch.<name>.remote and branch.<name>.merge. If the upstream
625 branch of A is origin/B sometimes we say "A is tracking origin/B".
626 working tree
628 The tree of actual checked out files. The working tree normally
629 contains the contents of the HEAD commit’s tree, plus any local
630 changes that you have made but not yet committed.
631 worktree
633 A repository can have zero (i.e. bare repository) or one or more
634 worktrees attached to it. One "worktree" consists of a "working
635 tree" and repository metadata, most of which are shared among other
636 worktrees of a single repository, and some of which are maintained
637 separately per worktree (e.g. the index, HEAD and pseudorefs like
638 MERGE_HEAD, per-worktree refs and per-worktree configuration file).
639
641 gittutorial(7), gittutorial-2(7), gitcvs-migration(7), giteveryday(7),
642 The Git User’s Manual[1]
643
645 Part of the git(1) suite
646
648 1. The Git User’s Manual
649 file:///usr/share/doc/git/user-manual.html
650Git 2.39.1 2023-01-13 GITGLOSSARY(7)