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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>> can
6 inherit part of its <<def_object_database,object database>> from another
7 <<def_object_database,object database>>, which is called "alternate".
9 [[def_bare_repository]]bare repository::
10 A <<def_bare_repository,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 non-cyclical graph of revisions, i.e. the complete history of a
25 particular <<def_revision,revision>>, which is called the
26 branch <<def_head,head>>. The heads
27 are stored in `$GIT_DIR/refs/heads/`.
29 [[def_cache]]cache::
30 Obsolete for: <<def_index,index>>.
32 [[def_chain]]chain::
33 A list of objects, where each <<def_object,object>> in the list contains
34 a reference to its successor (for example, the successor of a
35 <<def_commit,commit>> could be one of its parents).
37 [[def_changeset]]changeset::
38 BitKeeper/cvsps speak for "<<def_commit,commit>>". Since git does not
39 store changes, but states, it really does not make sense to use the term
40 "changesets" with git.
42 [[def_checkout]]checkout::
43 The action of updating the <<def_working_tree,working tree>> to a
44 <<def_revision,revision>> which was stored in the
45 <<def_object_database,object database>>.
47 [[def_cherry-picking]]cherry-picking::
48 In <<def_SCM,SCM>> jargon, "cherry pick" means to choose a subset of
49 changes out of a series of changes (typically commits) and record them
50 as a new series of changes on top of different codebase. In GIT, this is
51 performed by "git cherry-pick" command to extract the change introduced
52 by an existing <<def_commit,commit>> and to record it based on the tip
53 of the current <<def_branch,branch>> as a new <<def_commit,commit>>.
55 [[def_clean]]clean::
56 A <<def_working_tree,working tree>> is <<def_clean,clean>>, if it
57 corresponds to the <<def_revision,revision>> referenced by the current
58 <<def_head,head>>. Also see "<<def_dirty,dirty>>".
60 [[def_commit]]commit::
61 As a verb: The action of storing the current state of the
62 <<def_index,index>> in the <<def_object_database,object database>>. The
63 result is a <<def_revision,revision>>. As a noun: Short hand for
64 <<def_commit_object,commit object>>.
66 [[def_commit_object]]commit object::
67 An <<def_object,object>> which contains the information about a
68 particular <<def_revision,revision>>, such as parents, committer,
69 author, date and the <<def_tree_object,tree object>> which corresponds
70 to the top <<def_directory,directory>> of the stored
71 <<def_revision,revision>>.
73 [[def_core_git]]core git::
74 Fundamental data structures and utilities of git. Exposes only limited
75 source code management tools.
77 [[def_DAG]]DAG::
78 Directed acyclic graph. The <<def_commit,commit>> objects form a
79 directed acyclic graph, because they have parents (directed), and the
80 graph of <<def_commit,commit>> objects is acyclic (there is no
81 <<def_chain,chain>> which begins and ends with the same
82 <<def_object,object>>).
84 [[def_dangling_object]]dangling object::
85 An <<def_unreachable_object,unreachable object>> which is not
86 <<def_reachable,reachable>> even from other unreachable objects; a
87 <<def_dangling_object,dangling object>> has no references to it from any
88 reference or <<def_object,object>> in the <<def_repository,repository>>.
90 [[def_dircache]]dircache::
91 You are *waaaaay* behind.
93 [[def_directory]]directory::
94 The list you get with "ls" :-)
96 [[def_dirty]]dirty::
97 A <<def_working_tree,working tree>> is said to be <<def_dirty,dirty>> if
98 it contains modifications which have not been committed to the current
99 <<def_branch,branch>>.
101 [[def_ent]]ent::
102 Favorite synonym to "<<def_tree-ish,tree-ish>>" by some total geeks. See
103 `http://en.wikipedia.org/wiki/Ent_(Middle-earth)` for an in-depth
104 explanation. Avoid this term, not to confuse people.
106 [[def_fast_forward]]fast forward::
107 A fast-forward is a special type of <<def_merge,merge>> where you have a
108 <<def_revision,revision>> and you are "merging" another
109 <<def_branch,branch>>'s changes that happen to be a descendant of what
110 you have. In such these cases, you do not make a new <<def_merge,merge>>
111 <<def_commit,commit>> but instead just update to his
112 <<def_revision,revision>>. This will happen frequently on a
113 <<def_tracking_branch,tracking branch>> of a remote
114 <<def_repository,repository>>.
116 [[def_fetch]]fetch::
117 Fetching a <<def_branch,branch>> means to get the
118 <<def_branch,branch>>'s <<def_head_ref,head ref>> from a remote
119 <<def_repository,repository>>, to find out which objects are missing
120 from the local <<def_object_database,object database>>, and to get them,
121 too.
123 [[def_file_system]]file system::
124 Linus Torvalds originally designed git to be a user space file system,
125 i.e. the infrastructure to hold files and directories. That ensured the
126 efficiency and speed of git.
128 [[def_git_archive]]git archive::
129 Synonym for <<def_repository,repository>> (for arch people).
131 [[def_grafts]]grafts::
132 Grafts enables two otherwise different lines of development to be joined
133 together by recording fake ancestry information for commits. This way
134 you can make git pretend the set of parents a <<def_commit,commit>> has
135 is different from what was recorded when the <<def_commit,commit>> was
136 created. Configured via the `.git/info/grafts` file.
138 [[def_hash]]hash::
139 In git's context, synonym to <<def_object_name,object name>>.
141 [[def_head]]head::
142 The top of a <<def_branch,branch>>. It contains a <<def_ref,ref>> to the
143 corresponding <<def_commit_object,commit object>>.
145 [[def_head_ref]]head ref::
146 A <<def_ref,ref>> pointing to a <<def_head,head>>. Often, this is
147 abbreviated to "<<def_head,head>>". Head refs are stored in
148 `$GIT_DIR/refs/heads/`.
150 [[def_hook]]hook::
151 During the normal execution of several git commands, call-outs are made
152 to optional scripts that allow a developer to add functionality or
153 checking. Typically, the hooks allow for a command to be pre-verified
154 and potentially aborted, and allow for a post-notification after the
155 operation is done. The <<def_hook,hook>> scripts are found in the
156 `$GIT_DIR/hooks/` <<def_directory,directory>>, and are enabled by simply
157 making them executable.
159 [[def_index]]index::
160 A collection of files with stat information, whose contents are stored
161 as objects. The <<def_index,index>> is a stored version of your working
162 <<def_tree,tree>>. Truth be told, it can also contain a second, and even
163 a third version of a <<def_working_tree,working tree>>, which are used
164 when merging.
166 [[def_index_entry]]index entry::
167 The information regarding a particular file, stored in the
168 <<def_index,index>>. An <<def_index_entry,index entry>> can be unmerged,
169 if a <<def_merge,merge>> was started, but not yet finished (i.e. if the
170 <<def_index,index>> contains multiple versions of that file).
172 [[def_master]]master::
173 The default development <<def_branch,branch>>. Whenever you create a git
174 <<def_repository,repository>>, a <<def_branch,branch>> named
175 "<<def_master,master>>" is created, and becomes the active
176 <<def_branch,branch>>. In most cases, this contains the local
177 development, though that is purely conventional and not required.
179 [[def_merge]]merge::
180 To <<def_merge,merge>> branches means to try to accumulate the changes
181 since a common ancestor and apply them to the first
182 <<def_branch,branch>>. An automatic <<def_merge,merge>> uses heuristics
183 to accomplish that. Evidently, an automatic <<def_merge,merge>> can
184 fail.
186 [[def_object]]object::
187 The unit of storage in git. It is uniquely identified by the
188 <<def_SHA1,SHA1>> of its contents. Consequently, an
189 <<def_object,object>> can not be changed.
191 [[def_object_database]]object database::
192 Stores a set of "objects", and an individual <<def_object,object>> is
193 identified by its <<def_object_name,object name>>. The objects usually
194 live in `$GIT_DIR/objects/`.
196 [[def_object_identifier]]object identifier::
197 Synonym for <<def_object_name,object name>>.
199 [[def_object_name]]object name::
200 The unique identifier of an <<def_object,object>>. The <<def_hash,hash>>
201 of the <<def_object,object>>'s contents using the Secure Hash Algorithm
202 1 and usually represented by the 40 character hexadecimal encoding of
203 the <<def_hash,hash>> of the <<def_object,object>> (possibly followed by
204 a white space).
206 [[def_object_type]]object type::
207 One of the identifiers
208 "<<def_commit,commit>>","<<def_tree,tree>>","<<def_tag,tag>>" or "<<def_blob_object,blob>>"
209 describing the type of an <<def_object,object>>.
211 [[def_octopus]]octopus::
212 To <<def_merge,merge>> more than two branches. Also denotes an
213 intelligent predator.
215 [[def_origin]]origin::
216 The default upstream <<def_repository,repository>>. Most projects have
217 at least one upstream project which they track. By default
218 '<<def_origin,origin>>' is used for that purpose. New upstream updates
219 will be fetched into remote tracking branches named
220 origin/name-of-upstream-branch, which you can see using
221 "git <<def_branch,branch>> -r".
223 [[def_pack]]pack::
224 A set of objects which have been compressed into one file (to save space
225 or to transmit them efficiently).
227 [[def_pack_index]]pack index::
228 The list of identifiers, and other information, of the objects in a
229 <<def_pack,pack>>, to assist in efficiently accessing the contents of a
230 <<def_pack,pack>>.
232 [[def_parent]]parent::
233 A <<def_commit_object,commit object>> contains a (possibly empty) list
234 of the logical predecessor(s) in the line of development, i.e. its
235 parents.
237 [[def_pickaxe]]pickaxe::
238 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore
239 routines that help select changes that add or delete a given text
240 string. With the --pickaxe-all option, it can be used to view the full
241 <<def_changeset,changeset>> that introduced or removed, say, a
242 particular line of text. See gitlink:git-diff[1].
244 [[def_plumbing]]plumbing::
245 Cute name for <<def_core_git,core git>>.
247 [[def_porcelain]]porcelain::
248 Cute name for programs and program suites depending on
249 <<def_core_git,core git>>, presenting a high level access to
250 <<def_core_git,core git>>. Porcelains expose more of a <<def_SCM,SCM>>
251 interface than the <<def_plumbing,plumbing>>.
253 [[def_pull]]pull::
254 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
255 <<def_merge,merge>> it.
257 [[def_push]]push::
258 Pushing a <<def_branch,branch>> means to get the <<def_branch,branch>>'s
259 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>,
260 find out if it is an ancestor to the <<def_branch,branch>>'s local
261 <<def_head_ref,head ref>> is a direct, and in that case, putting all
262 objects, which are <<def_reachable,reachable>> from the local
263 <<def_head_ref,head ref>>, and which are missing from the remote
264 <<def_repository,repository>>, into the remote
265 <<def_object_database,object database>>, and updating the remote
266 <<def_head_ref,head ref>>. If the remote <<def_head,head>> is not an
267 ancestor to the local <<def_head,head>>, the <<def_push,push>> fails.
269 [[def_reachable]]reachable::
270 All of the ancestors of a given <<def_commit,commit>> are said to be
271 <<def_reachable,reachable>> from that <<def_commit,commit>>. More
272 generally, one <<def_object,object>> is <<def_reachable,reachable>> from
273 another if we can reach the one from the other by a <<def_chain,chain>>
274 that follows <<def_tag,tags>> to whatever they tag,
275 <<def_commit_object,commits>> to their parents or trees, and
276 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>>
277 that they contain.
279 [[def_rebase]]rebase::
280 To reapply a series of changes from a <<def_branch,branch>> to a
281 different base, and reset the <<def_head,head>> of that branch
282 to the result.
284 [[def_ref]]ref::
285 A 40-byte hex representation of a <<def_SHA1,SHA1>> or a name that
286 denotes a particular <<def_object,object>>. These may be stored in
287 `$GIT_DIR/refs/`.
289 [[def_refspec]]refspec::
290 A <<def_refspec,refspec>> is used by <<def_fetch,fetch>> and
291 <<def_push,push>> to describe the mapping between remote <<def_ref,ref>>
292 and local <<def_ref,ref>>. They are combined with a colon in the format
293 <src>:<dst>, preceded by an optional plus sign, +. For example: `git
294 fetch $URL refs/heads/master:refs/heads/origin` means
295 "grab the master <<def_branch,branch>> <<def_head,head>>
296 from the $URL and store it as my origin
297 <<def_branch,branch>> <<def_head,head>>". And `git <<def_push,push>>
298 $URL refs/heads/master:refs/heads/to-upstream` means
299 "publish my master <<def_branch,branch>>
300 <<def_head,head>> as to-upstream <<def_branch,branch>> at $URL". See
301 also gitlink:git-push[1]
303 [[def_repository]]repository::
304 A collection of refs together with an <<def_object_database,object
305 database>> containing all objects which are <<def_reachable,reachable>>
306 from the refs, possibly accompanied by meta data from one or more
307 porcelains. A <<def_repository,repository>> can share an
308 <<def_object_database,object database>> with other repositories.
310 [[def_resolve]]resolve::
311 The action of fixing up manually what a failed automatic
312 <<def_merge,merge>> left behind.
314 [[def_revision]]revision::
315 A particular state of files and directories which was stored in the
316 <<def_object_database,object database>>. It is referenced by a
317 <<def_commit_object,commit object>>.
319 [[def_rewind]]rewind::
320 To throw away part of the development, i.e. to assign the
321 <<def_head,head>> to an earlier <<def_revision,revision>>.
323 [[def_SCM]]SCM::
324 Source code management (tool).
326 [[def_SHA1]]SHA1::
327 Synonym for <<def_object_name,object name>>.
329 [[def_shallow_repository]]shallow repository::
330 A <<def_shallow_repository,shallow repository>> has an incomplete
331 history some of whose commits have parents cauterized away (in other
332 words, git is told to pretend that these commits do not have the
333 parents, even though they are recorded in the <<def_commit_object,commit
334 object>>). This is sometimes useful when you are interested only in the
335 recent history of a project even though the real history recorded in the
336 upstream is much larger. A <<def_shallow_repository,shallow repository>>
337 is created by giving the `--depth` option to gitlink:git-clone[1], and
338 its history can be later deepened with gitlink:git-fetch[1].
340 [[def_symref]]symref::
341 Symbolic reference: instead of containing the <<def_SHA1,SHA1>> id
342 itself, it is of the format 'ref: refs/some/thing' and when
343 referenced, it recursively dereferences to this reference. 'HEAD' is a
344 prime example of a <<def_symref,symref>>. Symbolic references are
345 manipulated with the gitlink:git-symbolic-ref[1] command.
347 [[def_tag]]tag::
348 A <<def_ref,ref>> pointing to a <<def_tag,tag>> or
349 <<def_commit_object,commit object>>. In contrast to a <<def_head,head>>,
350 a tag is not changed by a <<def_commit,commit>>. Tags (not
351 <<def_tag_object,tag objects>>) are stored in `$GIT_DIR/refs/tags/`. A
352 git tag has nothing to do with a Lisp tag (which would be
353 called an <<def_object_type,object type>> in git's context). A
354 tag is most typically used to mark a particular point in the
355 <<def_commit,commit>> ancestry <<def_chain,chain>>.
357 [[def_tag_object]]tag object::
358 An <<def_object,object>> containing a <<def_ref,ref>> pointing to
359 another <<def_object,object>>, which can contain a message just like a
360 <<def_commit_object,commit object>>. It can also contain a (PGP)
361 signature, in which case it is called a "signed <<def_tag_object,tag
362 object>>".
364 [[def_topic_branch]]topic branch::
365 A regular git <<def_branch,branch>> that is used by a developer to
366 identify a conceptual line of development. Since branches are very easy
367 and inexpensive, it is often desirable to have several small branches
368 that each contain very well defined concepts or small incremental yet
369 related changes.
371 [[def_tracking_branch]]tracking branch::
372 A regular git <<def_branch,branch>> that is used to follow changes from
373 another <<def_repository,repository>>. A <<def_tracking_branch,tracking
374 branch>> should not contain direct modifications or have local commits
375 made to it. A <<def_tracking_branch,tracking branch>> can usually be
376 identified as the right-hand-side <<def_ref,ref>> in a Pull:
377 <<def_refspec,refspec>>.
379 [[def_tree]]tree::
380 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree
381 object>> together with the dependent blob and <<def_tree,tree>> objects
382 (i.e. a stored representation of a <<def_working_tree,working tree>>).
384 [[def_tree_object]]tree object::
385 An <<def_object,object>> containing a list of file names and modes along
386 with refs to the associated blob and/or tree objects. A
387 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>.
389 [[def_tree-ish]]tree-ish::
390 A <<def_ref,ref>> pointing to either a <<def_commit_object,commit
391 object>>, a <<def_tree_object,tree object>>, or a <<def_tag_object,tag
392 object>> pointing to a <<def_tag,tag>> or <<def_commit,commit>> or
393 <<def_tree_object,tree object>>.
395 [[def_unmerged_index]]unmerged index::
396 An <<def_index,index>> which contains unmerged
397 <<def_index_entry,index entries>>.
399 [[def_unreachable_object]]unreachable object::
400 An <<def_object,object>> which is not <<def_reachable,reachable>> from a
401 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference.
403 [[def_working_tree]]working tree::
404 The set of files and directories currently being worked on, i.e. you can
405 work in your <<def_working_tree,working tree>> without using git at all.