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
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 core Git
88 Fundamental data structures and utilities of Git. Exposes only
89 limited source code management tools.
90 DAG
92 Directed acyclic graph. The commit objects form a directed acyclic
93 graph, because they have parents (directed), and the graph of
94 commit objects is acyclic (there is no chain which begins and ends
95 with the same object).
96 dangling object
98 An unreachable object which is not reachable even from other
99 unreachable objects; a dangling object has no references to it from
100 any reference or object in the repository.
101 detached HEAD
103 Normally the HEAD stores the name of a branch, and commands that
104 operate on the history HEAD represents operate on the history
105 leading to the tip of the branch the HEAD points at. However, Git
106 also allows you to check out an arbitrary commit that isn’t
107 necessarily the tip of any particular branch. The HEAD in such a
108 state is called "detached".
109 Note that commands that operate on the history of the current
111 branch (e.g. git commit to build a new history on top of it) still
112 work while the HEAD is detached. They update the HEAD to point at
113 the tip of the updated history without affecting any branch.
114 Commands that update or inquire information about the current
115 branch (e.g. git branch --set-upstream-to that sets what remote
116 tracking branch the current branch integrates with) obviously do
117 not work, as there is no (real) current branch to ask about in this
118 state.
119 directory
121 The list you get with "ls" :-)
122 dirty
124 A working tree is said to be "dirty" if it contains modifications
125 which have not been committed to the current branch.
126 evil merge
128 An evil merge is a merge that introduces changes that do not appear
129 in any parent.
130 fast-forward
132 A fast-forward is a special type of merge where you have a revision
133 and you are "merging" another branch's changes that happen to be a
134 descendant of what you have. In such these cases, you do not make a
135 new mergecommit but instead just update to his revision. This will
136 happen frequently on a remote-tracking branch of a remote
137 repository.
138 fetch
140 Fetching a branch means to get the branch’s head ref from a remote
141 repository, to find out which objects are missing from the local
142 object database, and to get them, too. See also git-fetch(1).
143 file system
145 Linus Torvalds originally designed Git to be a user space file
146 system, i.e. the infrastructure to hold files and directories. That
147 ensured the efficiency and speed of Git.
148 Git archive
150 Synonym for repository (for arch people).
151 gitfile
153 A plain file .git at the root of a working tree that points at the
154 directory that is the real repository.
155 grafts
157 Grafts enables two otherwise different lines of development to be
158 joined together by recording fake ancestry information for commits.
159 This way you can make Git pretend the set of parents a commit has
160 is different from what was recorded when the commit was created.
161 Configured via the .git/info/grafts file.
162 hash
164 In Git’s context, synonym for object name.
165 head
167 A named reference to the commit at the tip of a branch. Heads are
168 stored in a file in $GIT_DIR/refs/heads/ directory, except when
169 using packed refs. (See git-pack-refs(1).)
170 HEAD
172 The current branch. In more detail: Your working tree is normally
173 derived from the state of the tree referred to by HEAD. HEAD is a
174 reference to one of the heads in your repository, except when using
175 a detached HEAD, in which case it directly references an arbitrary
176 commit.
177 head ref
179 A synonym for head.
180 hook
182 During the normal execution of several Git commands, call-outs are
183 made to optional scripts that allow a developer to add
184 functionality or checking. Typically, the hooks allow for a command
185 to be pre-verified and potentially aborted, and allow for a
186 post-notification after the operation is done. The hook scripts are
187 found in the $GIT_DIR/hooks/ directory, and are enabled by simply
188 removing the .sample suffix from the filename. In earlier versions
189 of Git you had to make them executable.
190 index
192 A collection of files with stat information, whose contents are
193 stored as objects. The index is a stored version of your working
194 tree. Truth be told, it can also contain a second, and even a third
195 version of a working tree, which are used when merging.
196 index entry
198 The information regarding a particular file, stored in the index.
199 An index entry can be unmerged, if a merge was started, but not yet
200 finished (i.e. if the index contains multiple versions of that
201 file).
202 master
204 The default development branch. Whenever you create a Git
205 repository, a branch named "master" is created, and becomes the
206 active branch. In most cases, this contains the local development,
207 though that is purely by convention and is not required.
208 merge
210 As a verb: To bring the contents of another branch (possibly from
211 an external repository) into the current branch. In the case where
212 the merged-in branch is from a different repository, this is done
213 by first fetching the remote branch and then merging the result
214 into the current branch. This combination of fetch and merge
215 operations is called a pull. Merging is performed by an automatic
216 process that identifies changes made since the branches diverged,
217 and then applies all those changes together. In cases where changes
218 conflict, manual intervention may be required to complete the
219 merge.
220 As a noun: unless it is a fast-forward, a successful merge results
222 in the creation of a new commit representing the result of the
223 merge, and having as parents the tips of the merged branches. This
224 commit is referred to as a "merge commit", or sometimes just a
225 "merge".
226 object
228 The unit of storage in Git. It is uniquely identified by the SHA-1
229 of its contents. Consequently, an object can not be changed.
230 object database
232 Stores a set of "objects", and an individual object is identified
233 by its object name. The objects usually live in $GIT_DIR/objects/.
234 object identifier
236 Synonym for object name.
237 object name
239 The unique identifier of an object. The object name is usually
240 represented by a 40 character hexadecimal string. Also colloquially
241 called SHA-1.
242 object type
244 One of the identifiers "commit", "tree", "tag" or "blob" describing
245 the type of an object.
246 octopus
248 To merge more than two branches.
249 origin
251 The default upstream repository. Most projects have at least one
252 upstream project which they track. By default origin is used for
253 that purpose. New upstream updates will be fetched into remote
254 remote-tracking branches named origin/name-of-upstream-branch,
255 which you can see using git branch -r.
256 pack
258 A set of objects which have been compressed into one file (to save
259 space or to transmit them efficiently).
260 pack index
262 The list of identifiers, and other information, of the objects in a
263 pack, to assist in efficiently accessing the contents of a pack.
264 pathspec
266 Pattern used to limit paths in Git commands.
267 Pathspecs are used on the command line of "git ls-files", "git
269 ls-tree", "git add", "git grep", "git diff", "git checkout", and
270 many other commands to limit the scope of operations to some subset
271 of the tree or worktree. See the documentation of each command for
272 whether paths are relative to the current directory or toplevel.
273 The pathspec syntax is as follows:
274 · any path matches itself
276 · the pathspec up to the last slash represents a directory
278 prefix. The scope of that pathspec is limited to that subtree.
279 · the rest of the pathspec is a pattern for the remainder of the
281 pathname. Paths relative to the directory prefix will be
282 matched against that pattern using fnmatch(3); in particular, *
283 and ?can match directory separators.
284 For example, Documentation/*.jpg will match all .jpg files in the
286 Documentation subtree, including
287 Documentation/chapter_1/figure_1.jpg.
288 A pathspec that begins with a colon : has special meaning. In the
290 short form, the leading colon : is followed by zero or more "magic
291 signature" letters (which optionally is terminated by another colon
292 :), and the remainder is the pattern to match against the path. The
293 optional colon that terminates the "magic signature" can be omitted
294 if the pattern begins with a character that cannot be a "magic
295 signature" and is not a colon.
296 In the long form, the leading colon : is followed by a open
298 parenthesis (, a comma-separated list of zero or more "magic
299 words", and a close parentheses ), and the remainder is the pattern
300 to match against the path.
301 The "magic signature" consists of an ASCII symbol that is not
303 alphanumeric. Currently only the slash / is recognized as a "magic
304 signature": it makes the pattern match from the root of the working
305 tree, even when you are running the command from inside a
306 subdirectory.
307 A pathspec with only a colon means "there is no pathspec". This
309 form should not be combined with other pathspec.
310 parent
312 A commit object contains a (possibly empty) list of the logical
313 predecessor(s) in the line of development, i.e. its parents.
314 pickaxe
316 The term pickaxe refers to an option to the diffcore routines that
317 help select changes that add or delete a given text string. With
318 the --pickaxe-all option, it can be used to view the full changeset
319 that introduced or removed, say, a particular line of text. See
320 git-diff(1).
321 plumbing
323 Cute name for core Git.
324 porcelain
326 Cute name for programs and program suites depending on core Git,
327 presenting a high level access to core Git. Porcelains expose more
328 of a SCM interface than the plumbing.
329 pull
331 Pulling a branch means to fetch it and merge it. See also git-
332 pull(1).
333 push
335 Pushing a branch means to get the branch’s head ref from a remote
336 repository, find out if it is a direct ancestor to the branch’s
337 local head ref, and in that case, putting all objects, which are
338 reachable from the local head ref, and which are missing from the
339 remote repository, into the remote object database, and updating
340 the remote head ref. If the remote head is not an ancestor to the
341 local head, the push fails.
342 reachable
344 All of the ancestors of a given commit are said to be "reachable"
345 from that commit. More generally, one object is reachable from
346 another if we can reach the one from the other by a chain that
347 follows tags to whatever they tag, commits to their parents or
348 trees, and trees to the trees or blobs that they contain.
349 rebase
351 To reapply a series of changes from a branch to a different base,
352 and reset the head of that branch to the result.
353 ref
355 A 40-byte hex representation of a SHA-1 or a name that denotes a
356 particular object. They may be stored in a file under
357 $GIT_DIR/refs/ directory, or in the $GIT_DIR/packed-refs file.
358 reflog
360 A reflog shows the local "history" of a ref. In other words, it can
361 tell you what the 3rd last revision in this repository was, and
362 what was the current state in this repository, yesterday 9:14pm.
363 See git-reflog(1) for details.
364 refspec
366 A "refspec" is used by fetch and push to describe the mapping
367 between remote ref and local ref.
368 remote-tracking branch
370 A regular Git branch that is used to follow changes from another
371 repository. A remote-tracking branch should not contain direct
372 modifications or have local commits made to it. A remote-tracking
373 branch can usually be identified as the right-hand-side ref in a
374 Pull: refspec.
375 repository
377 A collection of refs together with an object database containing
378 all objects which are reachable from the refs, possibly accompanied
379 by meta data from one or more porcelains. A repository can share an
380 object database with other repositories via alternates mechanism.
381 resolve
383 The action of fixing up manually what a failed automatic merge left
384 behind.
385 revision
387 Synonym for commit (the noun).
388 rewind
390 To throw away part of the development, i.e. to assign the head to
391 an earlier revision.
392 SCM
394 Source code management (tool).
395 SHA-1
397 "Secure Hash Algorithm 1"; a cryptographic hash function. In the
398 context of Git used as a synonym for object name.
399 shallow repository
401 A shallow repository has an incomplete history some of whose
402 commits have parents cauterized away (in other words, Git is told
403 to pretend that these commits do not have the parents, even though
404 they are recorded in the commit object). This is sometimes useful
405 when you are interested only in the recent history of a project
406 even though the real history recorded in the upstream is much
407 larger. A shallow repository is created by giving the --depth
408 option to git-clone(1), and its history can be later deepened with
409 git-fetch(1).
410 symref
412 Symbolic reference: instead of containing the SHA-1 id itself, it
413 is of the format ref: refs/some/thing and when referenced, it
414 recursively dereferences to this reference. HEAD is a prime
415 example of a symref. Symbolic references are manipulated with the
416 git-symbolic-ref(1) command.
417 tag
419 A ref under refs/tags/ namespace that points to an object of an
420 arbitrary type (typically a tag points to either a tag or a commit
421 object). In contrast to a head, a tag is not updated by the commit
422 command. A Git tag has nothing to do with a Lisp tag (which would
423 be called an object type in Git’s context). A tag is most typically
424 used to mark a particular point in the commit ancestry chain.
425 tag object
427 An object containing a ref pointing to another object, which can
428 contain a message just like a commit object. It can also contain a
429 (PGP) signature, in which case it is called a "signed tag object".
430 topic branch
432 A regular Git branch that is used by a developer to identify a
433 conceptual line of development. Since branches are very easy and
434 inexpensive, it is often desirable to have several small branches
435 that each contain very well defined concepts or small incremental
436 yet related changes.
437 tree
439 Either a working tree, or a tree object together with the dependent
440 blob and tree objects (i.e. a stored representation of a working
441 tree).
442 tree object
444 An object containing a list of file names and modes along with refs
445 to the associated blob and/or tree objects. A tree is equivalent to
446 a directory.
447 tree-ish
449 A ref pointing to either a commit object, a tree object, or a tag
450 object pointing to a tag or commit or tree object.
451 unmerged index
453 An index which contains unmerged index entries.
454 unreachable object
456 An object which is not reachable from a branch, tag, or any other
457 reference.
458 upstream branch
460 The default branch that is merged into the branch in question (or
461 the branch in question is rebased onto). It is configured via
462 branch.<name>.remote and branch.<name>.merge. If the upstream
463 branch of A is origin/B sometimes we say "A is tracking origin/B".
464 working tree
466 The tree of actual checked out files. The working tree normally
467 contains the contents of the HEAD commit’s tree, plus any local
468 changes that you have made but not yet committed.
469
471 gittutorial(7), gittutorial-2(7), gitcvs-migration(7), Everyday Git[1],
472 The Git User’s Manual[2]
473
475 Part of the git(1) suite.
476
478 1. Everyday Git
479 file:///usr/share/doc/git-1.8.3.1/everyday.html
480 2. The Git User’s Manual
482 file:///usr/share/doc/git-1.8.3.1/user-manual.html
483Git 1.8.3.1 11/19/2018 GITGLOSSARY(7)