1GITGLOSSARY(7) Git Manual GITGLOSSARY(7)
2
6 gitglossary - A Git Glossary
7
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 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 dereference
122 Referring to a symbolic ref: the action of accessing the reference
123 pointed at by a symbolic ref. Recursive dereferencing involves
124 repeating the aforementioned process on the resulting ref until a
125 non-symbolic reference is found.
126 Referring to a tag object: the action of accessing the object a tag
128 points at. Tags are recursively dereferenced by repeating the
129 operation on the result object until the result has either a
130 specified object type (where applicable) or any non-"tag" object
131 type. A synonym for "recursive dereference" in the context of tags
132 is "peel".
133 Referring to a commit object: the action of accessing the commit’s
135 tree object. Commits cannot be dereferenced recursively.
136 Unless otherwise specified, "dereferencing" as it used in the
138 context of Git commands or protocols is implicitly recursive.
139 detached HEAD
141 Normally the HEAD stores the name of a branch, and commands that
142 operate on the history HEAD represents operate on the history
143 leading to the tip of the branch the HEAD points at. However, Git
144 also allows you to check out an arbitrary commit that isn’t
145 necessarily the tip of any particular branch. The HEAD in such a
146 state is called "detached".
147 Note that commands that operate on the history of the current
149 branch (e.g. git commit to build a new history on top of it) still
150 work while the HEAD is detached. They update the HEAD to point at
151 the tip of the updated history without affecting any branch.
152 Commands that update or inquire information about the current
153 branch (e.g. git branch --set-upstream-to that sets what
154 remote-tracking branch the current branch integrates with)
155 obviously do not work, as there is no (real) current branch to ask
156 about in this state.
157 directory
159 The list you get with "ls" :-)
160 dirty
162 A working tree is said to be "dirty" if it contains modifications
163 which have not been committed to the current branch.
164 evil merge
166 An evil merge is a merge that introduces changes that do not appear
167 in any parent.
168 fast-forward
170 A fast-forward is a special type of merge where you have a revision
171 and you are "merging" another branch's changes that happen to be a
172 descendant of what you have. In such a case, you do not make a new
173 merge commit but instead just update your branch to point at the
174 same revision as the branch you are merging. This will happen
175 frequently on a remote-tracking branch of a remote repository.
176 fetch
178 Fetching a branch means to get the branch’s head ref from a remote
179 repository, to find out which objects are missing from the local
180 object database, and to get them, too. See also git-fetch(1).
181 file system
183 Linus Torvalds originally designed Git to be a user space file
184 system, i.e. the infrastructure to hold files and directories. That
185 ensured the efficiency and speed of Git.
186 Git archive
188 Synonym for repository (for arch people).
189 gitfile
191 A plain file .git at the root of a working tree that points at the
192 directory that is the real repository.
193 grafts
195 Grafts enable two otherwise different lines of development to be
196 joined together by recording fake ancestry information for commits.
197 This way you can make Git pretend the set of parents a commit has
198 is different from what was recorded when the commit was created.
199 Configured via the .git/info/grafts file.
200 Note that the grafts mechanism is outdated and can lead to problems
202 transferring objects between repositories; see git-replace(1) for a
203 more flexible and robust system to do the same thing.
204 hash
206 In Git’s context, synonym for object name.
207 head
209 A named reference to the commit at the tip of a branch. Heads are
210 stored in a file in $GIT_DIR/refs/heads/ directory, except when
211 using packed refs. (See git-pack-refs(1).)
212 HEAD
214 The current branch. In more detail: Your working tree is normally
215 derived from the state of the tree referred to by HEAD. HEAD is a
216 reference to one of the heads in your repository, except when using
217 a detached HEAD, in which case it directly references an arbitrary
218 commit.
219 head ref
221 A synonym for head.
222 hook
224 During the normal execution of several Git commands, call-outs are
225 made to optional scripts that allow a developer to add
226 functionality or checking. Typically, the hooks allow for a command
227 to be pre-verified and potentially aborted, and allow for a
228 post-notification after the operation is done. The hook scripts are
229 found in the $GIT_DIR/hooks/ directory, and are enabled by simply
230 removing the .sample suffix from the filename. In earlier versions
231 of Git you had to make them executable.
232 index
234 A collection of files with stat information, whose contents are
235 stored as objects. The index is a stored version of your working
236 tree. Truth be told, it can also contain a second, and even a third
237 version of a working tree, which are used when merging.
238 index entry
240 The information regarding a particular file, stored in the index.
241 An index entry can be unmerged, if a merge was started, but not yet
242 finished (i.e. if the index contains multiple versions of that
243 file).
244 master
246 The default development branch. Whenever you create a Git
247 repository, a branch named "master" is created, and becomes the
248 active branch. In most cases, this contains the local development,
249 though that is purely by convention and is not required.
250 merge
252 As a verb: To bring the contents of another branch (possibly from
253 an external repository) into the current branch. In the case where
254 the merged-in branch is from a different repository, this is done
255 by first fetching the remote branch and then merging the result
256 into the current branch. This combination of fetch and merge
257 operations is called a pull. Merging is performed by an automatic
258 process that identifies changes made since the branches diverged,
259 and then applies all those changes together. In cases where changes
260 conflict, manual intervention may be required to complete the
261 merge.
262 As a noun: unless it is a fast-forward, a successful merge results
264 in the creation of a new commit representing the result of the
265 merge, and having as parents the tips of the merged branches. This
266 commit is referred to as a "merge commit", or sometimes just a
267 "merge".
268 object
270 The unit of storage in Git. It is uniquely identified by the SHA-1
271 of its contents. Consequently, an object cannot be changed.
272 object database
274 Stores a set of "objects", and an individual object is identified
275 by its object name. The objects usually live in $GIT_DIR/objects/.
276 object identifier (oid)
278 Synonym for object name.
279 object name
281 The unique identifier of an object. The object name is usually
282 represented by a 40 character hexadecimal string. Also colloquially
283 called SHA-1.
284 object type
286 One of the identifiers "commit", "tree", "tag" or "blob" describing
287 the type of an object.
288 octopus
290 To merge more than two branches.
291 origin
293 The default upstream repository. Most projects have at least one
294 upstream project which they track. By default origin is used for
295 that purpose. New upstream updates will be fetched into
296 remote-tracking branches named origin/name-of-upstream-branch,
297 which you can see using git branch -r.
298 overlay
300 Only update and add files to the working directory, but don’t
301 delete them, similar to how cp -R would update the contents in the
302 destination directory. This is the default mode in a checkout when
303 checking out files from the index or a tree-ish. In contrast,
304 no-overlay mode also deletes tracked files not present in the
305 source, similar to rsync --delete.
306 pack
308 A set of objects which have been compressed into one file (to save
309 space or to transmit them efficiently).
310 pack index
312 The list of identifiers, and other information, of the objects in a
313 pack, to assist in efficiently accessing the contents of a pack.
314 pathspec
316 Pattern used to limit paths in Git commands.
317 Pathspecs are used on the command line of "git ls-files", "git
319 ls-tree", "git add", "git grep", "git diff", "git checkout", and
320 many other commands to limit the scope of operations to some subset
321 of the tree or working tree. See the documentation of each command
322 for whether paths are relative to the current directory or
323 toplevel. The pathspec syntax is as follows:
324 • any path matches itself
326 • the pathspec up to the last slash represents a directory
328 prefix. The scope of that pathspec is limited to that subtree.
329 • the rest of the pathspec is a pattern for the remainder of the
331 pathname. Paths relative to the directory prefix will be
332 matched against that pattern using fnmatch(3); in particular, *
333 and ? can match directory separators.
334 For example, Documentation/*.jpg will match all .jpg files in the
336 Documentation subtree, including
337 Documentation/chapter_1/figure_1.jpg.
338 A pathspec that begins with a colon : has special meaning. In the
340 short form, the leading colon : is followed by zero or more "magic
341 signature" letters (which optionally is terminated by another colon
342 :), and the remainder is the pattern to match against the path. The
343 "magic signature" consists of ASCII symbols that are neither
344 alphanumeric, glob, regex special characters nor colon. The
345 optional colon that terminates the "magic signature" can be omitted
346 if the pattern begins with a character that does not belong to
347 "magic signature" symbol set and is not a colon.
348 In the long form, the leading colon : is followed by an open
350 parenthesis (, a comma-separated list of zero or more "magic
351 words", and a close parentheses ), and the remainder is the pattern
352 to match against the path.
353 A pathspec with only a colon means "there is no pathspec". This
355 form should not be combined with other pathspec.
356 top
358 The magic word top (magic signature: /) makes the pattern match
359 from the root of the working tree, even when you are running
360 the command from inside a subdirectory.
361 literal
363 Wildcards in the pattern such as * or ? are treated as literal
364 characters.
365 icase
367 Case insensitive match.
368 glob
370 Git treats the pattern as a shell glob suitable for consumption
371 by fnmatch(3) with the FNM_PATHNAME flag: wildcards in the
372 pattern will not match a / in the pathname. For example,
373 "Documentation/*.html" matches "Documentation/git.html" but not
374 "Documentation/ppc/ppc.html" or
375 "tools/perf/Documentation/perf.html".
376 Two consecutive asterisks ("**") in patterns matched against
378 full pathname may have special meaning:
379 • A leading "**" followed by a slash means match in all
381 directories. For example, "**/foo" matches file or
382 directory "foo" anywhere, the same as pattern "foo".
383 "**/foo/bar" matches file or directory "bar" anywhere that
384 is directly under directory "foo".
385 • A trailing "/**" matches everything inside. For example,
387 "abc/**" matches all files inside directory "abc", relative
388 to the location of the .gitignore file, with infinite
389 depth.
390 • A slash followed by two consecutive asterisks then a slash
392 matches zero or more directories. For example, "a/**/b"
393 matches "a/b", "a/x/b", "a/x/y/b" and so on.
394 • Other consecutive asterisks are considered invalid.
396 Glob magic is incompatible with literal magic.
398 attr
400 After attr: comes a space separated list of "attribute
401 requirements", all of which must be met in order for the path
402 to be considered a match; this is in addition to the usual
403 non-magic pathspec pattern matching. See gitattributes(5).
404 Each of the attribute requirements for the path takes one of
406 these forms:
407 • "ATTR" requires that the attribute ATTR be set.
409 • "-ATTR" requires that the attribute ATTR be unset.
411 • "ATTR=VALUE" requires that the attribute ATTR be set to the
413 string VALUE.
414 • "!ATTR" requires that the attribute ATTR be unspecified.
416 Note that when matching against a tree object, attributes
418 are still obtained from working tree, not from the given
419 tree object.
420 exclude
422 After a path matches any non-exclude pathspec, it will be run
423 through all exclude pathspecs (magic signature: ! or its
424 synonym ^). If it matches, the path is ignored. When there is
425 no non-exclude pathspec, the exclusion is applied to the result
426 set as if invoked without any pathspec.
427 parent
429 A commit object contains a (possibly empty) list of the logical
430 predecessor(s) in the line of development, i.e. its parents.
431 peel
433 The action of recursively dereferencing a tag object.
434 pickaxe
436 The term pickaxe refers to an option to the diffcore routines that
437 help select changes that add or delete a given text string. With
438 the --pickaxe-all option, it can be used to view the full changeset
439 that introduced or removed, say, a particular line of text. See
440 git-diff(1).
441 plumbing
443 Cute name for core Git.
444 porcelain
446 Cute name for programs and program suites depending on core Git,
447 presenting a high level access to core Git. Porcelains expose more
448 of a SCM interface than the plumbing.
449 per-worktree ref
451 Refs that are per-worktree, rather than global. This is presently
452 only HEAD and any refs that start with refs/bisect/, but might
453 later include other unusual refs.
454 pseudoref
456 Pseudorefs are a class of files under $GIT_DIR which behave like
457 refs for the purposes of rev-parse, but which are treated specially
458 by git. Pseudorefs both have names that are all-caps, and always
459 start with a line consisting of a SHA-1 followed by whitespace. So,
460 HEAD is not a pseudoref, because it is sometimes a symbolic ref.
461 They might optionally contain some additional data. MERGE_HEAD and
462 CHERRY_PICK_HEAD are examples. Unlike per-worktree refs, these
463 files cannot be symbolic refs, and never have reflogs. They also
464 cannot be updated through the normal ref update machinery. Instead,
465 they are updated by directly writing to the files. However, they
466 can be read as if they were refs, so git rev-parse MERGE_HEAD will
467 work.
468 pull
470 Pulling a branch means to fetch it and merge it. See also git-
471 pull(1).
472 push
474 Pushing a branch means to get the branch’s head ref from a remote
475 repository, find out if it is an ancestor to the branch’s local
476 head ref, and in that case, putting all objects, which are
477 reachable from the local head ref, and which are missing from the
478 remote repository, into the remote object database, and updating
479 the remote head ref. If the remote head is not an ancestor to the
480 local head, the push fails.
481 reachable
483 All of the ancestors of a given commit are said to be "reachable"
484 from that commit. More generally, one object is reachable from
485 another if we can reach the one from the other by a chain that
486 follows tags to whatever they tag, commits to their parents or
487 trees, and trees to the trees or blobs that they contain.
488 reachability bitmaps
490 Reachability bitmaps store information about the reachability of a
491 selected set of commits in a packfile, or a multi-pack index
492 (MIDX), to speed up object search. The bitmaps are stored in a
493 ".bitmap" file. A repository may have at most one bitmap file in
494 use. The bitmap file may belong to either one pack, or the
495 repository’s multi-pack index (if it exists).
496 rebase
498 To reapply a series of changes from a branch to a different base,
499 and reset the head of that branch to the result.
500 ref
502 A name that begins with refs/ (e.g. refs/heads/master) that points
503 to an object name or another ref (the latter is called a symbolic
504 ref). For convenience, a ref can sometimes be abbreviated when used
505 as an argument to a Git command; see gitrevisions(7) for details.
506 Refs are stored in the repository.
507 The ref namespace is hierarchical. Different subhierarchies are
509 used for different purposes (e.g. the refs/heads/ hierarchy is used
510 to represent local branches).
511 There are a few special-purpose refs that do not begin with refs/.
513 The most notable example is HEAD.
514 reflog
516 A reflog shows the local "history" of a ref. In other words, it can
517 tell you what the 3rd last revision in this repository was, and
518 what was the current state in this repository, yesterday 9:14pm.
519 See git-reflog(1) for details.
520 refspec
522 A "refspec" is used by fetch and push to describe the mapping
523 between remote ref and local ref.
524 remote repository
526 A repository which is used to track the same project but resides
527 somewhere else. To communicate with remotes, see fetch or push.
528 remote-tracking branch
530 A ref that is used to follow changes from another repository. It
531 typically looks like refs/remotes/foo/bar (indicating that it
532 tracks a branch named bar in a remote named foo), and matches the
533 right-hand-side of a configured fetch refspec. A remote-tracking
534 branch should not contain direct modifications or have local
535 commits made to it.
536 repository
538 A collection of refs together with an object database containing
539 all objects which are reachable from the refs, possibly accompanied
540 by meta data from one or more porcelains. A repository can share an
541 object database with other repositories via alternates mechanism.
542 resolve
544 The action of fixing up manually what a failed automatic merge left
545 behind.
546 revision
548 Synonym for commit (the noun).
549 rewind
551 To throw away part of the development, i.e. to assign the head to
552 an earlier revision.
553 SCM
555 Source code management (tool).
556 SHA-1
558 "Secure Hash Algorithm 1"; a cryptographic hash function. In the
559 context of Git used as a synonym for object name.
560 shallow clone
562 Mostly a synonym to shallow repository but the phrase makes it more
563 explicit that it was created by running git clone --depth=...
564 command.
565 shallow repository
567 A shallow repository has an incomplete history some of whose
568 commits have parents cauterized away (in other words, Git is told
569 to pretend that these commits do not have the parents, even though
570 they are recorded in the commit object). This is sometimes useful
571 when you are interested only in the recent history of a project
572 even though the real history recorded in the upstream is much
573 larger. A shallow repository is created by giving the --depth
574 option to git-clone(1), and its history can be later deepened with
575 git-fetch(1).
576 stash entry
578 An object used to temporarily store the contents of a dirty working
579 directory and the index for future reuse.
580 submodule
582 A repository that holds the history of a separate project inside
583 another repository (the latter of which is called superproject).
584 superproject
586 A repository that references repositories of other projects in its
587 working tree as submodules. The superproject knows about the names
588 of (but does not hold copies of) commit objects of the contained
589 submodules.
590 symref
592 Symbolic reference: instead of containing the SHA-1 id itself, it
593 is of the format ref: refs/some/thing and when referenced, it
594 recursively dereferences to this reference. HEAD is a prime
595 example of a symref. Symbolic references are manipulated with the
596 git-symbolic-ref(1) command.
597 tag
599 A ref under refs/tags/ namespace that points to an object of an
600 arbitrary type (typically a tag points to either a tag or a commit
601 object). In contrast to a head, a tag is not updated by the commit
602 command. A Git tag has nothing to do with a Lisp tag (which would
603 be called an object type in Git’s context). A tag is most typically
604 used to mark a particular point in the commit ancestry chain.
605 tag object
607 An object containing a ref pointing to another object, which can
608 contain a message just like a commit object. It can also contain a
609 (PGP) signature, in which case it is called a "signed tag object".
610 topic branch
612 A regular Git branch that is used by a developer to identify a
613 conceptual line of development. Since branches are very easy and
614 inexpensive, it is often desirable to have several small branches
615 that each contain very well defined concepts or small incremental
616 yet related changes.
617 tree
619 Either a working tree, or a tree object together with the dependent
620 blob and tree objects (i.e. a stored representation of a working
621 tree).
622 tree object
624 An object containing a list of file names and modes along with refs
625 to the associated blob and/or tree objects. A tree is equivalent to
626 a directory.
627 tree-ish (also treeish)
629 A tree object or an object that can be recursively dereferenced to
630 a tree object. Dereferencing a commit object yields the tree object
631 corresponding to the revision's top directory. The following are
632 all tree-ishes: a commit-ish, a tree object, a tag object that
633 points to a tree object, a tag object that points to a tag object
634 that points to a tree object, etc.
635 unmerged index
637 An index which contains unmerged index entries.
638 unreachable object
640 An object which is not reachable from a branch, tag, or any other
641 reference.
642 upstream branch
644 The default branch that is merged into the branch in question (or
645 the branch in question is rebased onto). It is configured via
646 branch.<name>.remote and branch.<name>.merge. If the upstream
647 branch of A is origin/B sometimes we say "A is tracking origin/B".
648 working tree
650 The tree of actual checked out files. The working tree normally
651 contains the contents of the HEAD commit’s tree, plus any local
652 changes that you have made but not yet committed.
653 worktree
655 A repository can have zero (i.e. bare repository) or one or more
656 worktrees attached to it. One "worktree" consists of a "working
657 tree" and repository metadata, most of which are shared among other
658 worktrees of a single repository, and some of which are maintained
659 separately per worktree (e.g. the index, HEAD and pseudorefs like
660 MERGE_HEAD, per-worktree refs and per-worktree configuration file).
661
663 gittutorial(7), gittutorial-2(7), gitcvs-migration(7), giteveryday(7),
664 The Git User’s Manual[1]
665
667 Part of the git(1) suite
668
670 1. The Git User’s Manual
671 file:///usr/share/doc/git/user-manual.html
672Git 2.43.0 11/20/2023 GITGLOSSARY(7)