Fix silly typo in new builtin grep
[git/git.git] / Documentation / glossary.txt
1 object::
2 The unit of storage in git. It is uniquely identified by
3 the SHA1 of its contents. Consequently, an object can not
4 be changed.
5
6 object name::
7 The unique identifier of an object. The hash of the object's contents
8 using the Secure Hash Algorithm 1 and usually represented by the 40
9 character hexadecimal encoding of the hash of the object (possibly
10 followed by a white space).
11
12 SHA1::
13 Synonym for object name.
14
15 object identifier::
16 Synonym for object name.
17
18 hash::
19 In git's context, synonym to object name.
20
21 object database::
22 Stores a set of "objects", and an individual object is identified
23 by its object name. The objects usually live in `$GIT_DIR/objects/`.
24
25 blob object::
26 Untyped object, e.g. the contents of a file.
27
28 tree object::
29 An object containing a list of file names and modes along with refs
30 to the associated blob and/or tree objects. A tree is equivalent
31 to a directory.
32
33 tree::
34 Either a working tree, or a tree object together with the
35 dependent blob and tree objects (i.e. a stored representation
36 of a working tree).
37
38 DAG::
39 Directed acyclic graph. The commit objects form a directed acyclic
40 graph, because they have parents (directed), and the graph of commit
41 objects is acyclic (there is no chain which begins and ends with the
42 same object).
43
44 index::
45 A collection of files with stat information, whose contents are
46 stored as objects. The index is a stored version of your working
47 tree. Truth be told, it can also contain a second, and even a third
48 version of a working tree, which are used when merging.
49
50 index entry::
51 The information regarding a particular file, stored in the index.
52 An index entry can be unmerged, if a merge was started, but not
53 yet finished (i.e. if the index contains multiple versions of
54 that file).
55
56 unmerged index:
57 An index which contains unmerged index entries.
58
59 cache::
60 Obsolete for: index.
61
62 working tree::
63 The set of files and directories currently being worked on,
64 i.e. you can work in your working tree without using git at all.
65
66 directory::
67 The list you get with "ls" :-)
68
69 revision::
70 A particular state of files and directories which was stored in
71 the object database. It is referenced by a commit object.
72
73 checkout::
74 The action of updating the working tree to a revision which was
75 stored in the object database.
76
77 commit::
78 As a verb: The action of storing the current state of the index in the
79 object database. The result is a revision.
80 As a noun: Short hand for commit object.
81
82 commit object::
83 An object which contains the information about a particular
84 revision, such as parents, committer, author, date and the
85 tree object which corresponds to the top directory of the
86 stored revision.
87
88 parent::
89 A commit object contains a (possibly empty) list of the logical
90 predecessor(s) in the line of development, i.e. its parents.
91
92 changeset::
93 BitKeeper/cvsps speak for "commit". Since git does not store
94 changes, but states, it really does not make sense to use
95 the term "changesets" with git.
96
97 clean::
98 A working tree is clean, if it corresponds to the revision
99 referenced by the current head.
100
101 dirty::
102 A working tree is said to be dirty if it contains modifications
103 which have not been committed to the current branch.
104
105 head::
106 The top of a branch. It contains a ref to the corresponding
107 commit object.
108
109 branch::
110 A non-cyclical graph of revisions, i.e. the complete history of
111 a particular revision, which is called the branch head. The
112 branch heads are stored in `$GIT_DIR/refs/heads/`.
113
114 master::
115 The default branch. Whenever you create a git repository, a branch
116 named "master" is created, and becomes the active branch. In most
117 cases, this contains the local development.
118
119 origin::
120 The default upstream branch. Most projects have one upstream
121 project which they track, and by default 'origin' is used for
122 that purpose. New updates from upstream will be fetched into
123 this branch; you should never commit to it yourself.
124
125 ref::
126 A 40-byte hex representation of a SHA1 pointing to a particular
127 object. These may be stored in `$GIT_DIR/refs/`.
128
129 head ref::
130 A ref pointing to a head. Often, this is abbreviated to "head".
131 Head refs are stored in `$GIT_DIR/refs/heads/`.
132
133 tree-ish::
134 A ref pointing to either a commit object, a tree object, or a
135 tag object pointing to a tag or commit or tree object.
136
137 ent::
138 Favorite synonym to "tree-ish" by some total geeks. See
139 `http://en.wikipedia.org/wiki/Ent_(Middle-earth)` for an in-depth
140 explanation.
141
142 tag object::
143 An object containing a ref pointing to another object, which can
144 contain a message just like a commit object. It can also
145 contain a (PGP) signature, in which case it is called a "signed
146 tag object".
147
148 tag::
149 A ref pointing to a tag or commit object. In contrast to a head,
150 a tag is not changed by a commit. Tags (not tag objects) are
151 stored in `$GIT_DIR/refs/tags/`. A git tag has nothing to do with
152 a Lisp tag (which is called object type in git's context).
153 A tag is most typically used to mark a particular point in the
154 commit ancestry chain.
155
156 merge::
157 To merge branches means to try to accumulate the changes since a
158 common ancestor and apply them to the first branch. An automatic
159 merge uses heuristics to accomplish that. Evidently, an automatic
160 merge can fail.
161
162 octopus::
163 To merge more than two branches. Also denotes an intelligent
164 predator.
165
166 resolve::
167 The action of fixing up manually what a failed automatic merge
168 left behind.
169
170 rewind::
171 To throw away part of the development, i.e. to assign the head to
172 an earlier revision.
173
174 rebase::
175 To clean a branch by starting from the head of the main line of
176 development ("master"), and reapply the (possibly cherry-picked)
177 changes from that branch.
178
179 repository::
180 A collection of refs together with an object database containing
181 all objects, which are reachable from the refs, possibly accompanied
182 by meta data from one or more porcelains. A repository can
183 share an object database with other repositories.
184
185 git archive::
186 Synonym for repository (for arch people).
187
188 file system::
189 Linus Torvalds originally designed git to be a user space file
190 system, i.e. the infrastructure to hold files and directories.
191 That ensured the efficiency and speed of git.
192
193 alternate object database::
194 Via the alternates mechanism, a repository can inherit part of its
195 object database from another object database, which is called
196 "alternate".
197
198 reachable::
199 An object is reachable from a ref/commit/tree/tag, if there is a
200 chain leading from the latter to the former.
201
202 chain::
203 A list of objects, where each object in the list contains a
204 reference to its successor (for example, the successor of a commit
205 could be one of its parents).
206
207 fetch::
208 Fetching a branch means to get the branch's head ref from a
209 remote repository, to find out which objects are missing from
210 the local object database, and to get them, too.
211
212 pull::
213 Pulling a branch means to fetch it and merge it.
214
215 push::
216 Pushing a branch means to get the branch's head ref from a remote
217 repository, find out if it is an ancestor to the branch's local
218 head ref is a direct, and in that case, putting all objects, which
219 are reachable from the local head ref, and which are missing from
220 the remote repository, into the remote object database, and updating
221 the remote head ref. If the remote head is not an ancestor to the
222 local head, the push fails.
223
224 pack::
225 A set of objects which have been compressed into one file (to save
226 space or to transmit them efficiently).
227
228 pack index::
229 The list of identifiers, and other information, of the objects in a
230 pack, to assist in efficiently accessing the contents of a pack.
231
232 core git::
233 Fundamental data structures and utilities of git. Exposes only
234 limited source code management tools.
235
236 plumbing::
237 Cute name for core git.
238
239 porcelain::
240 Cute name for programs and program suites depending on core git,
241 presenting a high level access to core git. Porcelains expose
242 more of a SCM interface than the plumbing.
243
244 object type:
245 One of the identifiers "commit","tree","tag" and "blob" describing
246 the type of an object.
247
248 SCM::
249 Source code management (tool).
250
251 dircache::
252 You are *waaaaay* behind.
253