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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 <<def_revision,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 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 the <<def_working_tree,working tree>> to a
49 <<def_revision,revision>> which was stored in the
50 <<def_object_database,object database>>.
52 [[def_cherry-picking]]cherry-picking::
53 In <<def_SCM,SCM>> jargon, "cherry pick" means to choose a subset of
54 changes out of a series of changes (typically commits) and record them
55 as a new series of changes on top of different codebase. In GIT, this is
56 performed by "git cherry-pick" command to extract the change introduced
57 by an existing <<def_commit,commit>> and to record it based on the tip
58 of the current <<def_branch,branch>> as a new commit.
60 [[def_clean]]clean::
61 A <<def_working_tree,working tree>> is clean, if it
62 corresponds to the <<def_revision,revision>> referenced by the current
63 <<def_head,head>>. Also see "<<def_dirty,dirty>>".
65 [[def_commit]]commit::
66 As a noun: A single point in the
67 git history; the entire history of a project is represented as a
68 set of interrelated commits. The word "commit" is often
69 used by git in the same places other revision control systems
70 use the words "revision" or "version". Also used as a short
71 hand for <<def_commit_object,commit object>>.
72 +
73 As a verb: The action of storing a new snapshot of the project's
74 state in the git history, by creating a new commit representing the current
75 state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>>
76 to point at the new commit.
78 [[def_commit_object]]commit object::
79 An <<def_object,object>> which contains the information about a
80 particular <<def_revision,revision>>, such as parents, committer,
81 author, date and the <<def_tree_object,tree object>> which corresponds
82 to the top <<def_directory,directory>> of the stored
83 <<def_revision,revision>>.
85 [[def_core_git]]core git::
86 Fundamental data structures and utilities of git. Exposes only limited
87 source code management tools.
89 [[def_DAG]]DAG::
90 Directed acyclic graph. The <<def_commit,commit>> objects form a
91 directed acyclic graph, because they have parents (directed), and the
92 graph of commit objects is acyclic (there is no
93 <<def_chain,chain>> which begins and ends with the same
94 <<def_object,object>>).
96 [[def_dangling_object]]dangling object::
97 An <<def_unreachable_object,unreachable object>> which is not
98 <<def_reachable,reachable>> even from other unreachable objects; a
99 dangling object has no references to it from any
100 reference or <<def_object,object>> in the <<def_repository,repository>>.
102 [[def_detached_HEAD]]detached HEAD::
103 Normally the <<def_HEAD,HEAD>> stores the name of a
104 <<def_branch,branch>>. However, git also allows you to check
105 out an arbitrary commit that isn't necessarily the tip of any
106 particular branch. In this case HEAD is said to be "detached".
108 [[def_dircache]]dircache::
109 You are *waaaaay* behind.
111 [[def_directory]]directory::
112 The list you get with "ls" :-)
114 [[def_dirty]]dirty::
115 A <<def_working_tree,working tree>> is said to be "dirty" if
116 it contains modifications which have not been committed to the current
117 <<def_branch,branch>>.
119 [[def_ent]]ent::
120 Favorite synonym to "<<def_tree-ish,tree-ish>>" by some total geeks. See
121 `http://en.wikipedia.org/wiki/Ent_(Middle-earth)` for an in-depth
122 explanation. Avoid this term, not to confuse people.
124 [[def_fast_forward]]fast forward::
125 A fast-forward is a special type of <<def_merge,merge>> where you have a
126 <<def_revision,revision>> and you are "merging" another
127 <<def_branch,branch>>'s changes that happen to be a descendant of what
128 you have. In such these cases, you do not make a new <<def_merge,merge>>
129 <<def_commit,commit>> but instead just update to his
130 revision. This will happen frequently on a
131 <<def_tracking_branch,tracking branch>> of a remote
132 <<def_repository,repository>>.
134 [[def_fetch]]fetch::
135 Fetching a <<def_branch,branch>> means to get the
136 branch's <<def_head_ref,head ref>> from a remote
137 <<def_repository,repository>>, to find out which objects are
138 missing from the local <<def_object_database,object database>>,
139 and to get them, too. See also gitlink:git-fetch[1].
141 [[def_file_system]]file system::
142 Linus Torvalds originally designed git to be a user space file system,
143 i.e. the infrastructure to hold files and directories. That ensured the
144 efficiency and speed of git.
146 [[def_git_archive]]git archive::
147 Synonym for <<def_repository,repository>> (for arch people).
149 [[def_grafts]]grafts::
150 Grafts enables two otherwise different lines of development to be joined
151 together by recording fake ancestry information for commits. This way
152 you can make git pretend the set of parents a <<def_commit,commit>> has
153 is different from what was recorded when the commit was
154 created. Configured via the `.git/info/grafts` file.
156 [[def_hash]]hash::
157 In git's context, synonym to <<def_object_name,object name>>.
159 [[def_head]]head::
160 A named reference to the <<def_commit,commit>> at the tip of a
161 <<def_branch,branch>>. Heads are stored in
162 `$GIT_DIR/refs/heads/`, except when using packed refs. (See
163 gitlink:git-pack-refs[1].)
165 [[def_HEAD]]HEAD::
166 The current branch. In more detail: Your <<def_working_tree,
167 working tree>> is normally derived from the state of the tree
168 referred to by HEAD. HEAD is a reference to one of the
169 <<def_head,heads>> in your repository, except when using a
170 <<def_detached_HEAD,detached HEAD>>, in which case it may
171 reference an arbitrary commit.
173 [[def_head_ref]]head ref::
174 A synonym for <<def_head,head>>.
176 [[def_hook]]hook::
177 During the normal execution of several git commands, call-outs are made
178 to optional scripts that allow a developer to add functionality or
179 checking. Typically, the hooks allow for a command to be pre-verified
180 and potentially aborted, and allow for a post-notification after the
181 operation is done. The hook scripts are found in the
182 `$GIT_DIR/hooks/` <<def_directory,directory>>, and are enabled by simply
183 making them executable.
185 [[def_index]]index::
186 A collection of files with stat information, whose contents are stored
187 as objects. The index is a stored version of your working
188 <<def_tree,tree>>. Truth be told, it can also contain a second, and even
189 a third version of a <<def_working_tree,working tree>>, which are used
190 when merging.
192 [[def_index_entry]]index entry::
193 The information regarding a particular file, stored in the
194 <<def_index,index>>. An index entry can be unmerged, if a
195 <<def_merge,merge>> was started, but not yet finished (i.e. if
196 the index contains multiple versions of that file).
198 [[def_master]]master::
199 The default development <<def_branch,branch>>. Whenever you
200 create a git <<def_repository,repository>>, a branch named
201 "master" is created, and becomes the active branch. In most
202 cases, this contains the local development, though that is
203 purely by convention and is not required.
205 [[def_merge]]merge::
206 As a verb: To bring the contents of another
207 <<def_branch,branch>> (possibly from an external
208 <<def_repository,repository>>) into the current branch. In the
209 case where the merged-in branch is from a different repository,
210 this is done by first <<def_fetch,fetching>> the remote branch
211 and then merging the result into the current branch. This
212 combination of fetch and merge operations is called a
213 <<def_pull,pull>>. Merging is performed by an automatic process
214 that identifies changes made since the branches diverged, and
215 then applies all those changes together. In cases where changes
216 conflict, manual intervention may be required to complete the
217 merge.
218 +
219 As a noun: unless it is a <<def_fast_forward,fast forward>>, a
220 successful merge results in the creation of a new <<def_commit,commit>>
221 representing the result of the merge, and having as
222 <<def_parent,parents>> the tips of the merged <<def_branch,branches>>.
223 This commit is referred to as a "merge commit", or sometimes just a
224 "merge".
226 [[def_object]]object::
227 The unit of storage in git. It is uniquely identified by the
228 <<def_SHA1,SHA1>> of its contents. Consequently, an
229 object can not be changed.
231 [[def_object_database]]object database::
232 Stores a set of "objects", and an individual <<def_object,object>> is
233 identified by its <<def_object_name,object name>>. The objects usually
234 live in `$GIT_DIR/objects/`.
236 [[def_object_identifier]]object identifier::
237 Synonym for <<def_object_name,object name>>.
239 [[def_object_name]]object name::
240 The unique identifier of an <<def_object,object>>. The <<def_hash,hash>>
241 of the object's contents using the Secure Hash Algorithm
242 1 and usually represented by the 40 character hexadecimal encoding of
243 the <<def_hash,hash>> of the object (possibly followed by
244 a white space).
246 [[def_object_type]]object type::
247 One of the identifiers
248 "<<def_commit,commit>>","<<def_tree,tree>>","<<def_tag,tag>>" or "<<def_blob_object,blob>>"
249 describing the type of an <<def_object,object>>.
251 [[def_octopus]]octopus::
252 To <<def_merge,merge>> more than two branches. Also denotes an
253 intelligent predator.
255 [[def_origin]]origin::
256 The default upstream <<def_repository,repository>>. Most projects have
257 at least one upstream project which they track. By default
258 'origin' is used for that purpose. New upstream updates
259 will be fetched into remote tracking branches named
260 origin/name-of-upstream-branch, which you can see using
261 "git <<def_branch,branch>> -r".
263 [[def_pack]]pack::
264 A set of objects which have been compressed into one file (to save space
265 or to transmit them efficiently).
267 [[def_pack_index]]pack index::
268 The list of identifiers, and other information, of the objects in a
269 <<def_pack,pack>>, to assist in efficiently accessing the contents of a
270 pack.
272 [[def_parent]]parent::
273 A <<def_commit_object,commit object>> contains a (possibly empty) list
274 of the logical predecessor(s) in the line of development, i.e. its
275 parents.
277 [[def_pickaxe]]pickaxe::
278 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore
279 routines that help select changes that add or delete a given text
280 string. With the --pickaxe-all option, it can be used to view the full
281 <<def_changeset,changeset>> that introduced or removed, say, a
282 particular line of text. See gitlink:git-diff[1].
284 [[def_plumbing]]plumbing::
285 Cute name for <<def_core_git,core git>>.
287 [[def_porcelain]]porcelain::
288 Cute name for programs and program suites depending on
289 <<def_core_git,core git>>, presenting a high level access to
290 core git. Porcelains expose more of a <<def_SCM,SCM>>
291 interface than the <<def_plumbing,plumbing>>.
293 [[def_pull]]pull::
294 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
295 <<def_merge,merge>> it. See also gitlink:git-pull[1].
297 [[def_push]]push::
298 Pushing a <<def_branch,branch>> means to get the branch's
299 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>,
300 find out if it is an ancestor to the branch's local
301 head ref is a direct, and in that case, putting all
302 objects, which are <<def_reachable,reachable>> from the local
303 head ref, and which are missing from the remote
304 repository, into the remote
305 <<def_object_database,object database>>, and updating the remote
306 head ref. If the remote <<def_head,head>> is not an
307 ancestor to the local head, the push fails.
309 [[def_reachable]]reachable::
310 All of the ancestors of a given <<def_commit,commit>> are said to be
311 "reachable" from that commit. More
312 generally, one <<def_object,object>> is reachable from
313 another if we can reach the one from the other by a <<def_chain,chain>>
314 that follows <<def_tag,tags>> to whatever they tag,
315 <<def_commit_object,commits>> to their parents or trees, and
316 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>>
317 that they contain.
319 [[def_rebase]]rebase::
320 To reapply a series of changes from a <<def_branch,branch>> to a
321 different base, and reset the <<def_head,head>> of that branch
322 to the result.
324 [[def_ref]]ref::
325 A 40-byte hex representation of a <<def_SHA1,SHA1>> or a name that
326 denotes a particular <<def_object,object>>. These may be stored in
327 `$GIT_DIR/refs/`.
329 [[def_refspec]]refspec::
330 A <<def_refspec,refspec>> is used by <<def_fetch,fetch>> and
331 <<def_push,push>> to describe the mapping between remote
332 <<def_ref,ref>> and local ref. They are combined with a colon in
333 the format <src>:<dst>, preceded by an optional plus sign, +.
334 For example: `git fetch $URL
335 refs/heads/master:refs/heads/origin` means "grab the master
336 <<def_branch,branch>> <<def_head,head>> from the $URL and store
337 it as my origin branch head". And `git push
338 $URL refs/heads/master:refs/heads/to-upstream` means "publish my
339 master branch head as to-upstream branch at $URL". See also
340 gitlink:git-push[1]
342 [[def_repository]]repository::
343 A collection of refs together with an
344 <<def_object_database,object database>> containing all objects
345 which are <<def_reachable,reachable>> from the refs, possibly
346 accompanied by meta data from one or more porcelains. A
347 repository can share an object database with other repositories.
349 [[def_resolve]]resolve::
350 The action of fixing up manually what a failed automatic
351 <<def_merge,merge>> left behind.
353 [[def_revision]]revision::
354 A particular state of files and directories which was stored in the
355 <<def_object_database,object database>>. It is referenced by a
356 <<def_commit_object,commit object>>.
358 [[def_rewind]]rewind::
359 To throw away part of the development, i.e. to assign the
360 <<def_head,head>> to an earlier <<def_revision,revision>>.
362 [[def_SCM]]SCM::
363 Source code management (tool).
365 [[def_SHA1]]SHA1::
366 Synonym for <<def_object_name,object name>>.
368 [[def_shallow_repository]]shallow repository::
369 A shallow repository has an incomplete
370 history some of whose commits have parents cauterized away (in other
371 words, git is told to pretend that these commits do not have the
372 parents, even though they are recorded in the <<def_commit_object,commit
373 object>>). This is sometimes useful when you are interested only in the
374 recent history of a project even though the real history recorded in the
375 upstream is much larger. A shallow repository
376 is created by giving the `--depth` option to gitlink:git-clone[1], and
377 its history can be later deepened with gitlink:git-fetch[1].
379 [[def_symref]]symref::
380 Symbolic reference: instead of containing the <<def_SHA1,SHA1>>
381 id itself, it is of the format 'ref: refs/some/thing' and when
382 referenced, it recursively dereferences to this reference.
383 '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic
384 references are manipulated with the gitlink:git-symbolic-ref[1]
385 command.
387 [[def_tag]]tag::
388 A <<def_ref,ref>> pointing to a tag or
389 <<def_commit_object,commit object>>. In contrast to a <<def_head,head>>,
390 a tag is not changed by a <<def_commit,commit>>. Tags (not
391 <<def_tag_object,tag objects>>) are stored in `$GIT_DIR/refs/tags/`. A
392 git tag has nothing to do with a Lisp tag (which would be
393 called an <<def_object_type,object type>> in git's context). A
394 tag is most typically used to mark a particular point in the
395 commit ancestry <<def_chain,chain>>.
397 [[def_tag_object]]tag object::
398 An <<def_object,object>> containing a <<def_ref,ref>> pointing to
399 another object, which can contain a message just like a
400 <<def_commit_object,commit object>>. It can also contain a (PGP)
401 signature, in which case it is called a "signed <<def_tag_object,tag
402 object>>".
404 [[def_topic_branch]]topic branch::
405 A regular git <<def_branch,branch>> that is used by a developer to
406 identify a conceptual line of development. Since branches are very easy
407 and inexpensive, it is often desirable to have several small branches
408 that each contain very well defined concepts or small incremental yet
409 related changes.
411 [[def_tracking_branch]]tracking branch::
412 A regular git <<def_branch,branch>> that is used to follow changes from
413 another <<def_repository,repository>>. A tracking
414 branch should not contain direct modifications or have local commits
415 made to it. A tracking branch can usually be
416 identified as the right-hand-side <<def_ref,ref>> in a Pull:
417 <<def_refspec,refspec>>.
419 [[def_tree]]tree::
420 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree
421 object>> together with the dependent blob and tree objects
422 (i.e. a stored representation of a working tree).
424 [[def_tree_object]]tree object::
425 An <<def_object,object>> containing a list of file names and modes along
426 with refs to the associated blob and/or tree objects. A
427 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>.
429 [[def_tree-ish]]tree-ish::
430 A <<def_ref,ref>> pointing to either a <<def_commit_object,commit
431 object>>, a <<def_tree_object,tree object>>, or a <<def_tag_object,tag
432 object>> pointing to a tag or commit or tree object.
434 [[def_unmerged_index]]unmerged index::
435 An <<def_index,index>> which contains unmerged
436 <<def_index_entry,index entries>>.
438 [[def_unreachable_object]]unreachable object::
439 An <<def_object,object>> which is not <<def_reachable,reachable>> from a
440 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference.
442 [[def_working_tree]]working tree::
443 The tree of actual checked out files. The working tree is
444 normally equal to the <<def_HEAD,HEAD>> plus any local changes
445 that you have made but not yet committed.