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1 GIT Glossary
2 ============
4 [[def_alternate_object_database]]alternate object database::
5 Via the alternates mechanism, a <<def_repository,repository>>
6 can inherit part of its <<def_object_database,object database>>
7 from another object database, which is called "alternate".
9 [[def_bare_repository]]bare repository::
10 A bare repository is normally an appropriately
11 named <<def_directory,directory>> with a `.git` suffix that does not
12 have a locally checked-out copy of any of the files under
13 revision control. That is, all of the `git`
14 administrative and control files that would normally be present in the
15 hidden `.git` sub-directory are directly present in the
16 `repository.git` directory instead,
17 and no other files are present and checked out. Usually publishers of
18 public repositories make bare repositories available.
20 [[def_blob_object]]blob object::
21 Untyped <<def_object,object>>, e.g. the contents of a file.
23 [[def_branch]]branch::
24 A "branch" is an active line of development. The most recent
25 <<def_commit,commit>> on a branch is referred to as the tip of
26 that branch. The tip of the branch is referenced by a branch
27 <<def_head,head>>, which moves forward as additional development
28 is done on the branch. A single git
29 <<def_repository,repository>> can track an arbitrary number of
30 branches, but your <<def_working_tree,working tree>> is
31 associated with just one of them (the "current" or "checked out"
32 branch), and <<def_HEAD,HEAD>> points to that branch.
34 [[def_cache]]cache::
35 Obsolete for: <<def_index,index>>.
37 [[def_chain]]chain::
38 A list of objects, where each <<def_object,object>> in the list contains
39 a reference to its successor (for example, the successor of a
40 <<def_commit,commit>> could be one of its <<def_parent,parents>>).
42 [[def_changeset]]changeset::
43 BitKeeper/cvsps speak for "<<def_commit,commit>>". Since git does not
44 store changes, but states, it really does not make sense to use the term
45 "changesets" with git.
47 [[def_checkout]]checkout::
48 The action of updating all or part of the
49 <<def_working_tree,working tree>> with a <<def_tree_object,tree object>>
50 or <<def_blob_object,blob>> from the
51 <<def_object_database,object database>>, and updating the
52 <<def_index,index>> and <<def_HEAD,HEAD>> if the whole working tree has
53 been pointed at a new <<def_branch,branch>>.
55 [[def_cherry-picking]]cherry-picking::
56 In <<def_SCM,SCM>> jargon, "cherry pick" means to choose a subset of
57 changes out of a series of changes (typically commits) and record them
58 as a new series of changes on top of a different codebase. In GIT, this is
59 performed by the "git cherry-pick" command to extract the change introduced
60 by an existing <<def_commit,commit>> and to record it based on the tip
61 of the current <<def_branch,branch>> as a new commit.
63 [[def_clean]]clean::
64 A <<def_working_tree,working tree>> is clean, if it
65 corresponds to the <<def_revision,revision>> referenced by the current
66 <<def_head,head>>. Also see "<<def_dirty,dirty>>".
68 [[def_commit]]commit::
69 As a noun: A single point in the
70 git history; the entire history of a project is represented as a
71 set of interrelated commits. The word "commit" is often
72 used by git in the same places other revision control systems
73 use the words "revision" or "version". Also used as a short
74 hand for <<def_commit_object,commit object>>.
75 +
76 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 current
78 state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>>
79 to point at the new commit.
81 [[def_commit_object]]commit object::
82 An <<def_object,object>> which contains the information about a
83 particular <<def_revision,revision>>, such as <<def_parent,parents>>, committer,
84 author, date and the <<def_tree_object,tree object>> which corresponds
85 to the top <<def_directory,directory>> of the stored
86 revision.
88 [[def_core_git]]core git::
89 Fundamental data structures and utilities of git. Exposes only limited
90 source code management tools.
92 [[def_DAG]]DAG::
93 Directed acyclic graph. The <<def_commit,commit>> objects form a
94 directed acyclic graph, because they have parents (directed), and the
95 graph of commit objects is acyclic (there is no
96 <<def_chain,chain>> which begins and ends with the same
97 <<def_object,object>>).
99 [[def_dangling_object]]dangling object::
100 An <<def_unreachable_object,unreachable object>> which is not
101 <<def_reachable,reachable>> even from other unreachable objects; a
102 dangling object has no references to it from any
103 reference or <<def_object,object>> in the <<def_repository,repository>>.
105 [[def_detached_HEAD]]detached HEAD::
106 Normally the <<def_HEAD,HEAD>> stores the name of a
107 <<def_branch,branch>>. However, git also allows you to <<def_checkout,check out>>
108 an arbitrary <<def_commit,commit>> that isn't necessarily the tip of any
109 particular branch. In this case HEAD is said to be "detached".
111 [[def_dircache]]dircache::
112 You are *waaaaay* behind. See <<def_index,index>>.
114 [[def_directory]]directory::
115 The list you get with "ls" :-)
117 [[def_dirty]]dirty::
118 A <<def_working_tree,working tree>> is said to be "dirty" if
119 it contains modifications which have not been <<def_commit,committed>> to the current
120 <<def_branch,branch>>.
122 [[def_ent]]ent::
123 Favorite synonym to "<<def_tree-ish,tree-ish>>" by some total geeks. See
124 `http://en.wikipedia.org/wiki/Ent_(Middle-earth)` for an in-depth
125 explanation. Avoid this term, not to confuse people.
127 [[def_evil_merge]]evil merge::
128 An evil merge is a <<def_merge,merge>> that introduces changes that
129 do not appear in any <<def_parent,parent>>.
131 [[def_fast_forward]]fast forward::
132 A fast-forward is a special type of <<def_merge,merge>> where you have a
133 <<def_revision,revision>> and you are "merging" another
134 <<def_branch,branch>>'s changes that happen to be a descendant of what
135 you have. In such these cases, you do not make a new <<def_merge,merge>>
136 <<def_commit,commit>> but instead just update to his
137 revision. This will happen frequently on a
138 <<def_tracking_branch,tracking branch>> of a remote
139 <<def_repository,repository>>.
141 [[def_fetch]]fetch::
142 Fetching a <<def_branch,branch>> means to get the
143 branch's <<def_head_ref,head ref>> from a remote
144 <<def_repository,repository>>, to find out which objects are
145 missing from the local <<def_object_database,object database>>,
146 and to get them, too. See also linkgit:git-fetch[1].
148 [[def_file_system]]file system::
149 Linus Torvalds originally designed git to be a user space file system,
150 i.e. the infrastructure to hold files and directories. That ensured the
151 efficiency and speed of git.
153 [[def_git_archive]]git archive::
154 Synonym for <<def_repository,repository>> (for arch people).
156 [[def_grafts]]grafts::
157 Grafts enables two otherwise different lines of development to be joined
158 together by recording fake ancestry information for commits. This way
159 you can make git pretend the set of <<def_parent,parents>> a <<def_commit,commit>> has
160 is different from what was recorded when the commit was
161 created. Configured via the `.git/info/grafts` file.
163 [[def_hash]]hash::
164 In git's context, synonym to <<def_object_name,object name>>.
166 [[def_head]]head::
167 A <<def_ref,named reference>> to the <<def_commit,commit>> at the tip of a
168 <<def_branch,branch>>. Heads are stored in
169 `$GIT_DIR/refs/heads/`, except when using packed refs. (See
170 linkgit:git-pack-refs[1].)
172 [[def_HEAD]]HEAD::
173 The current <<def_branch,branch>>. In more detail: Your <<def_working_tree,
174 working tree>> is normally derived from the state of the tree
175 referred to by HEAD. HEAD is a reference to one of the
176 <<def_head,heads>> in your repository, except when using a
177 <<def_detached_HEAD,detached HEAD>>, in which case it may
178 reference an arbitrary commit.
180 [[def_head_ref]]head ref::
181 A synonym for <<def_head,head>>.
183 [[def_hook]]hook::
184 During the normal execution of several git commands, call-outs are made
185 to optional scripts that allow a developer to add functionality or
186 checking. Typically, the hooks allow for a command to be pre-verified
187 and potentially aborted, and allow for a post-notification after the
188 operation is done. The hook scripts are found in the
189 `$GIT_DIR/hooks/` directory, and are enabled by simply
190 making them executable.
192 [[def_index]]index::
193 A collection of files with stat information, whose contents are stored
194 as objects. The index is a stored version of your
195 <<def_working_tree,working tree>>. Truth be told, it can also contain a second, and even
196 a third version of a working tree, which are used
197 when <<def_merge,merging>>.
199 [[def_index_entry]]index entry::
200 The information regarding a particular file, stored in the
201 <<def_index,index>>. An index entry can be unmerged, if a
202 <<def_merge,merge>> was started, but not yet finished (i.e. if
203 the index contains multiple versions of that file).
205 [[def_master]]master::
206 The default development <<def_branch,branch>>. Whenever you
207 create a git <<def_repository,repository>>, a branch named
208 "master" is created, and becomes the active branch. In most
209 cases, this contains the local development, though that is
210 purely by convention and is not required.
212 [[def_merge]]merge::
213 As a verb: To bring the contents of another
214 <<def_branch,branch>> (possibly from an external
215 <<def_repository,repository>>) into the current branch. In the
216 case where the merged-in branch is from a different repository,
217 this is done by first <<def_fetch,fetching>> the remote branch
218 and then merging the result into the current branch. This
219 combination of fetch and merge operations is called a
220 <<def_pull,pull>>. Merging is performed by an automatic process
221 that identifies changes made since the branches diverged, and
222 then applies all those changes together. In cases where changes
223 conflict, manual intervention may be required to complete the
224 merge.
225 +
226 As a noun: unless it is a <<def_fast_forward,fast forward>>, a
227 successful merge results in the creation of a new <<def_commit,commit>>
228 representing the result of the merge, and having as
229 <<def_parent,parents>> the tips of the merged <<def_branch,branches>>.
230 This commit is referred to as a "merge commit", or sometimes just a
231 "merge".
233 [[def_object]]object::
234 The unit of storage in git. It is uniquely identified by the
235 <<def_SHA1,SHA1>> of its contents. Consequently, an
236 object can not be changed.
238 [[def_object_database]]object database::
239 Stores a set of "objects", and an individual <<def_object,object>> is
240 identified by its <<def_object_name,object name>>. The objects usually
241 live in `$GIT_DIR/objects/`.
243 [[def_object_identifier]]object identifier::
244 Synonym for <<def_object_name,object name>>.
246 [[def_object_name]]object name::
247 The unique identifier of an <<def_object,object>>. The <<def_hash,hash>>
248 of the object's contents using the Secure Hash Algorithm
249 1 and usually represented by the 40 character hexadecimal encoding of
250 the <<def_hash,hash>> of the object.
252 [[def_object_type]]object type::
253 One of the identifiers
254 "<<def_commit,commit>>","<<def_tree,tree>>","<<def_tag,tag>>" or "<<def_blob_object,blob>>"
255 describing the type of an <<def_object,object>>.
257 [[def_octopus]]octopus::
258 To <<def_merge,merge>> more than two <<def_branch,branches>>. Also denotes an
259 intelligent predator.
261 [[def_origin]]origin::
262 The default upstream <<def_repository,repository>>. Most projects have
263 at least one upstream project which they track. By default
264 'origin' is used for that purpose. New upstream updates
265 will be fetched into remote <<def_tracking_branch,tracking branches>> named
266 origin/name-of-upstream-branch, which you can see using
267 "`git branch -r`".
269 [[def_pack]]pack::
270 A set of objects which have been compressed into one file (to save space
271 or to transmit them efficiently).
273 [[def_pack_index]]pack index::
274 The list of identifiers, and other information, of the objects in a
275 <<def_pack,pack>>, to assist in efficiently accessing the contents of a
276 pack.
278 [[def_parent]]parent::
279 A <<def_commit_object,commit object>> contains a (possibly empty) list
280 of the logical predecessor(s) in the line of development, i.e. its
281 parents.
283 [[def_pickaxe]]pickaxe::
284 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore
285 routines that help select changes that add or delete a given text
286 string. With the `--pickaxe-all` option, it can be used to view the full
287 <<def_changeset,changeset>> that introduced or removed, say, a
288 particular line of text. See linkgit:git-diff[1].
290 [[def_plumbing]]plumbing::
291 Cute name for <<def_core_git,core git>>.
293 [[def_porcelain]]porcelain::
294 Cute name for programs and program suites depending on
295 <<def_core_git,core git>>, presenting a high level access to
296 core git. Porcelains expose more of a <<def_SCM,SCM>>
297 interface than the <<def_plumbing,plumbing>>.
299 [[def_pull]]pull::
300 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
301 <<def_merge,merge>> it. See also linkgit:git-pull[1].
303 [[def_push]]push::
304 Pushing a <<def_branch,branch>> means to get the branch's
305 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>,
306 find out if it is a direct ancestor to the branch's local
307 head ref, and in that case, putting all
308 objects, which are <<def_reachable,reachable>> from the local
309 head ref, and which are missing from the remote
310 repository, into the remote
311 <<def_object_database,object database>>, and updating the remote
312 head ref. If the remote <<def_head,head>> is not an
313 ancestor to the local head, the push fails.
315 [[def_reachable]]reachable::
316 All of the ancestors of a given <<def_commit,commit>> are said to be
317 "reachable" from that commit. More
318 generally, one <<def_object,object>> is reachable from
319 another if we can reach the one from the other by a <<def_chain,chain>>
320 that follows <<def_tag,tags>> to whatever they tag,
321 <<def_commit_object,commits>> to their parents or trees, and
322 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>>
323 that they contain.
325 [[def_rebase]]rebase::
326 To reapply a series of changes from a <<def_branch,branch>> to a
327 different base, and reset the <<def_head,head>> of that branch
328 to the result.
330 [[def_ref]]ref::
331 A 40-byte hex representation of a <<def_SHA1,SHA1>> or a name that
332 denotes a particular <<def_object,object>>. These may be stored in
333 `$GIT_DIR/refs/`.
335 [[def_reflog]]reflog::
336 A reflog shows the local "history" of a ref. In other words,
337 it can tell you what the 3rd last revision in _this_ repository
338 was, and what was the current state in _this_ repository,
339 yesterday 9:14pm. See linkgit:git-reflog[1] for details.
341 [[def_refspec]]refspec::
342 A "refspec" is used by <<def_fetch,fetch>> and
343 <<def_push,push>> to describe the mapping between remote
344 <<def_ref,ref>> and local ref. They are combined with a colon in
345 the format <src>:<dst>, preceded by an optional plus sign, +.
346 For example: `git fetch $URL
347 refs/heads/master:refs/heads/origin` means "grab the master
348 <<def_branch,branch>> <<def_head,head>> from the $URL and store
349 it as my origin branch head". And `git push
350 $URL refs/heads/master:refs/heads/to-upstream` means "publish my
351 master branch head as to-upstream branch at $URL". See also
352 linkgit:git-push[1].
354 [[def_repository]]repository::
355 A collection of <<def_ref,refs>> together with an
356 <<def_object_database,object database>> containing all objects
357 which are <<def_reachable,reachable>> from the refs, possibly
358 accompanied by meta data from one or more <<def_porcelain,porcelains>>. A
359 repository can share an object database with other repositories
360 via <<def_alternate_object_database,alternates mechanism>>.
362 [[def_resolve]]resolve::
363 The action of fixing up manually what a failed automatic
364 <<def_merge,merge>> left behind.
366 [[def_revision]]revision::
367 A particular state of files and directories which was stored in the
368 <<def_object_database,object database>>. It is referenced by a
369 <<def_commit_object,commit object>>.
371 [[def_rewind]]rewind::
372 To throw away part of the development, i.e. to assign the
373 <<def_head,head>> to an earlier <<def_revision,revision>>.
375 [[def_SCM]]SCM::
376 Source code management (tool).
378 [[def_SHA1]]SHA1::
379 Synonym for <<def_object_name,object name>>.
381 [[def_shallow_repository]]shallow repository::
382 A shallow <<def_repository,repository>> has an incomplete
383 history some of whose <<def_commit,commits>> have <<def_parent,parents>> cauterized away (in other
384 words, git is told to pretend that these commits do not have the
385 parents, even though they are recorded in the <<def_commit_object,commit
386 object>>). This is sometimes useful when you are interested only in the
387 recent history of a project even though the real history recorded in the
388 upstream is much larger. A shallow repository
389 is created by giving the `--depth` option to linkgit:git-clone[1], and
390 its history can be later deepened with linkgit:git-fetch[1].
392 [[def_symref]]symref::
393 Symbolic reference: instead of containing the <<def_SHA1,SHA1>>
394 id itself, it is of the format 'ref: refs/some/thing' and when
395 referenced, it recursively dereferences to this reference.
396 '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic
397 references are manipulated with the linkgit:git-symbolic-ref[1]
398 command.
400 [[def_tag]]tag::
401 A <<def_ref,ref>> pointing to a <<def_tag_object,tag>> or
402 <<def_commit_object,commit object>>. In contrast to a <<def_head,head>>,
403 a tag is not changed by a <<def_commit,commit>>. Tags (not
404 <<def_tag_object,tag objects>>) are stored in `$GIT_DIR/refs/tags/`. A
405 git tag has nothing to do with a Lisp tag (which would be
406 called an <<def_object_type,object type>> in git's context). A
407 tag is most typically used to mark a particular point in the
408 commit ancestry <<def_chain,chain>>.
410 [[def_tag_object]]tag object::
411 An <<def_object,object>> containing a <<def_ref,ref>> pointing to
412 another object, which can contain a message just like a
413 <<def_commit_object,commit object>>. It can also contain a (PGP)
414 signature, in which case it is called a "signed tag object".
416 [[def_topic_branch]]topic branch::
417 A regular git <<def_branch,branch>> that is used by a developer to
418 identify a conceptual line of development. Since branches are very easy
419 and inexpensive, it is often desirable to have several small branches
420 that each contain very well defined concepts or small incremental yet
421 related changes.
423 [[def_tracking_branch]]tracking branch::
424 A regular git <<def_branch,branch>> that is used to follow changes from
425 another <<def_repository,repository>>. A tracking
426 branch should not contain direct modifications or have local commits
427 made to it. A tracking branch can usually be
428 identified as the right-hand-side <<def_ref,ref>> in a Pull:
429 <<def_refspec,refspec>>.
431 [[def_tree]]tree::
432 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree
433 object>> together with the dependent <<def_blob_object,blob>> and tree objects
434 (i.e. a stored representation of a working tree).
436 [[def_tree_object]]tree object::
437 An <<def_object,object>> containing a list of file names and modes along
438 with refs to the associated blob and/or tree objects. A
439 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>.
441 [[def_tree-ish]]tree-ish::
442 A <<def_ref,ref>> pointing to either a <<def_commit_object,commit
443 object>>, a <<def_tree_object,tree object>>, or a <<def_tag_object,tag
444 object>> pointing to a tag or commit or tree object.
446 [[def_unmerged_index]]unmerged index::
447 An <<def_index,index>> which contains unmerged
448 <<def_index_entry,index entries>>.
450 [[def_unreachable_object]]unreachable object::
451 An <<def_object,object>> which is not <<def_reachable,reachable>> from a
452 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference.
454 [[def_working_tree]]working tree::
455 The tree of actual checked out files. The working tree is
456 normally equal to the <<def_HEAD,HEAD>> plus any local changes
457 that you have made but not yet committed.