2c06ed34ad2ed72f9cf856fb617e54a1956da599
[git/git.git] / Documentation / revisions.txt
1 SPECIFYING REVISIONS
2 --------------------
3
4 A revision parameter '<rev>' typically, but not necessarily, names a
5 commit object. It uses what is called an 'extended SHA-1'
6 syntax. Here are various ways to spell object names. The
7 ones listed near the end of this list name trees and
8 blobs contained in a commit.
9
10 '<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
11 The full SHA-1 object name (40-byte hexadecimal string), or
12 a leading substring that is unique within the repository.
13 E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
14 name the same commit object if there is no other object in
15 your repository whose object name starts with dae86e.
16
17 '<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
18 Output from `git describe`; i.e. a closest tag, optionally
19 followed by a dash and a number of commits, followed by a dash, a
20 'g', and an abbreviated object name.
21
22 '<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
23 A symbolic ref name. E.g. 'master' typically means the commit
24 object referenced by 'refs/heads/master'. If you
25 happen to have both 'heads/master' and 'tags/master', you can
26 explicitly say 'heads/master' to tell Git which one you mean.
27 When ambiguous, a '<refname>' is disambiguated by taking the
28 first match in the following rules:
29
30 . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
31 useful only for 'HEAD', 'FETCH_HEAD', 'ORIG_HEAD', 'MERGE_HEAD'
32 and 'CHERRY_PICK_HEAD');
33
34 . otherwise, 'refs/<refname>' if it exists;
35
36 . otherwise, 'refs/tags/<refname>' if it exists;
37
38 . otherwise, 'refs/heads/<refname>' if it exists;
39
40 . otherwise, 'refs/remotes/<refname>' if it exists;
41
42 . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
43 +
44 'HEAD' names the commit on which you based the changes in the working tree.
45 'FETCH_HEAD' records the branch which you fetched from a remote repository
46 with your last `git fetch` invocation.
47 'ORIG_HEAD' is created by commands that move your 'HEAD' in a drastic
48 way, to record the position of the 'HEAD' before their operation, so that
49 you can easily change the tip of the branch back to the state before you ran
50 them.
51 'MERGE_HEAD' records the commit(s) which you are merging into your branch
52 when you run `git merge`.
53 'CHERRY_PICK_HEAD' records the commit which you are cherry-picking
54 when you run `git cherry-pick`.
55 +
56 Note that any of the 'refs/*' cases above may come either from
57 the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
58 While the ref name encoding is unspecified, UTF-8 is preferred as
59 some output processing may assume ref names in UTF-8.
60
61 '@'::
62 '@' alone is a shortcut for 'HEAD'.
63
64 '<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
65 A ref followed by the suffix '@' with a date specification
66 enclosed in a brace
67 pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
68 second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
69 of the ref at a prior point in time. This suffix may only be
70 used immediately following a ref name and the ref must have an
71 existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
72 of your *local* ref at a given time; e.g., what was in your local
73 'master' branch last week. If you want to look at commits made during
74 certain times, see '--since' and '--until'.
75
76 '<refname>@\{<n>\}', e.g. 'master@\{1\}'::
77 A ref followed by the suffix '@' with an ordinal specification
78 enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
79 the n-th prior value of that ref. For example 'master@\{1\}'
80 is the immediate prior value of 'master' while 'master@\{5\}'
81 is the 5th prior value of 'master'. This suffix may only be used
82 immediately following a ref name and the ref must have an existing
83 log ('$GIT_DIR/logs/<refname>').
84
85 '@\{<n>\}', e.g. '@\{1\}'::
86 You can use the '@' construct with an empty ref part to get at a
87 reflog entry of the current branch. For example, if you are on
88 branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
89
90 '@\{-<n>\}', e.g. '@\{-1\}'::
91 The construct '@\{-<n>\}' means the <n>th branch checked out
92 before the current one.
93
94 '<branchname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
95 The suffix '@\{upstream\}' to a branchname (short form '<branchname>@\{u\}')
96 refers to the branch that the branch specified by branchname is set to build on
97 top of. A missing branchname defaults to the current one.
98
99 '<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
100 A suffix '{caret}' to a revision parameter means the first parent of
101 that commit object. '{caret}<n>' means the <n>th parent (i.e.
102 '<rev>{caret}'
103 is equivalent to '<rev>{caret}1'). As a special rule,
104 '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
105 object name of a tag object that refers to a commit object.
106
107 '<rev>{tilde}<n>', e.g. 'master{tilde}3'::
108 A suffix '{tilde}<n>' to a revision parameter means the commit
109 object that is the <n>th generation ancestor of the named
110 commit object, following only the first parents. I.e. '<rev>{tilde}3' is
111 equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
112 '<rev>{caret}1{caret}1{caret}1'. See below for an illustration of
113 the usage of this form.
114
115 '<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
116 A suffix '{caret}' followed by an object type name enclosed in
117 brace pair means dereference the object at '<rev>' recursively until
118 an object of type '<type>' is found or the object cannot be
119 dereferenced anymore (in which case, barf).
120 For example, if '<rev>' is a commit-ish, '<rev>{caret}\{commit\}'
121 describes the corresponding commit object.
122 Similarly, if '<rev>' is a tree-ish, '<rev>{caret}\{tree\}'
123 describes the corresponding tree object.
124 '<rev>{caret}0'
125 is a short-hand for '<rev>{caret}\{commit\}'.
126 +
127 'rev{caret}\{object\}' can be used to make sure 'rev' names an
128 object that exists, without requiring 'rev' to be a tag, and
129 without dereferencing 'rev'; because a tag is already an object,
130 it does not have to be dereferenced even once to get to an object.
131 +
132 'rev{caret}\{tag\}' can be used to ensure that 'rev' identifies an
133 existing tag object.
134
135 '<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
136 A suffix '{caret}' followed by an empty brace pair
137 means the object could be a tag,
138 and dereference the tag recursively until a non-tag object is
139 found.
140
141 '<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
142 A suffix '{caret}' to a revision parameter, followed by a brace
143 pair that contains a text led by a slash,
144 is the same as the ':/fix nasty bug' syntax below except that
145 it returns the youngest matching commit which is reachable from
146 the '<rev>' before '{caret}'.
147
148 ':/<text>', e.g. ':/fix nasty bug'::
149 A colon, followed by a slash, followed by a text, names
150 a commit whose commit message matches the specified regular expression.
151 This name returns the youngest matching commit which is
152 reachable from any ref. If the commit message starts with a
153 '!' you have to repeat that; the special sequence ':/!',
154 followed by something else than '!', is reserved for now.
155 The regular expression can match any part of the commit message. To
156 match messages starting with a string, one can use e.g. ':/^foo'.
157
158 '<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
159 A suffix ':' followed by a path names the blob or tree
160 at the given path in the tree-ish object named by the part
161 before the colon.
162 ':path' (with an empty part before the colon)
163 is a special case of the syntax described next: content
164 recorded in the index at the given path.
165 A path starting with './' or '../' is relative to the current working directory.
166 The given path will be converted to be relative to the working tree's root directory.
167 This is most useful to address a blob or tree from a commit or tree that has
168 the same tree structure as the working tree.
169
170 ':<n>:<path>', e.g. ':0:README', ':README'::
171 A colon, optionally followed by a stage number (0 to 3) and a
172 colon, followed by a path, names a blob object in the
173 index at the given path. A missing stage number (and the colon
174 that follows it) names a stage 0 entry. During a merge, stage
175 1 is the common ancestor, stage 2 is the target branch's version
176 (typically the current branch), and stage 3 is the version from
177 the branch which is being merged.
178
179 Here is an illustration, by Jon Loeliger. Both commit nodes B
180 and C are parents of commit node A. Parent commits are ordered
181 left-to-right.
182
183 ........................................
184 G H I J
185 \ / \ /
186 D E F
187 \ | / \
188 \ | / |
189 \|/ |
190 B C
191 \ /
192 \ /
193 A
194 ........................................
195
196 A = = A^0
197 B = A^ = A^1 = A~1
198 C = A^2 = A^2
199 D = A^^ = A^1^1 = A~2
200 E = B^2 = A^^2
201 F = B^3 = A^^3
202 G = A^^^ = A^1^1^1 = A~3
203 H = D^2 = B^^2 = A^^^2 = A~2^2
204 I = F^ = B^3^ = A^^3^
205 J = F^2 = B^3^2 = A^^3^2
206
207
208 SPECIFYING RANGES
209 -----------------
210
211 History traversing commands such as `git log` operate on a set
212 of commits, not just a single commit. To these commands,
213 specifying a single revision with the notation described in the
214 previous section means the set of commits reachable from that
215 commit, following the commit ancestry chain.
216
217 To exclude commits reachable from a commit, a prefix '{caret}'
218 notation is used. E.g. '{caret}r1 r2' means commits reachable
219 from 'r2' but exclude the ones reachable from 'r1'.
220
221 This set operation appears so often that there is a shorthand
222 for it. When you have two commits 'r1' and 'r2' (named according
223 to the syntax explained in SPECIFYING REVISIONS above), you can ask
224 for commits that are reachable from r2 excluding those that are reachable
225 from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
226
227 A similar notation 'r1\...r2' is called symmetric difference
228 of 'r1' and 'r2' and is defined as
229 'r1 r2 --not $(git merge-base --all r1 r2)'.
230 It is the set of commits that are reachable from either one of
231 'r1' or 'r2' but not from both.
232
233 In these two shorthands, you can omit one end and let it default to HEAD.
234 For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
235 did I do since I forked from the origin branch?" Similarly, '..origin'
236 is a shorthand for 'HEAD..origin' and asks "What did the origin do since
237 I forked from them?" Note that '..' would mean 'HEAD..HEAD' which is an
238 empty range that is both reachable and unreachable from HEAD.
239
240 Two other shorthands for naming a set that is formed by a commit
241 and its parent commits exist. The 'r1{caret}@' notation means all
242 parents of 'r1'. 'r1{caret}!' includes commit 'r1' but excludes
243 all of its parents.
244
245 To summarize:
246
247 '<rev>'::
248 Include commits that are reachable from (i.e. ancestors of)
249 <rev>.
250
251 '{caret}<rev>'::
252 Exclude commits that are reachable from (i.e. ancestors of)
253 <rev>.
254
255 '<rev1>..<rev2>'::
256 Include commits that are reachable from <rev2> but exclude
257 those that are reachable from <rev1>. When either <rev1> or
258 <rev2> is omitted, it defaults to 'HEAD'.
259
260 '<rev1>\...<rev2>'::
261 Include commits that are reachable from either <rev1> or
262 <rev2> but exclude those that are reachable from both. When
263 either <rev1> or <rev2> is omitted, it defaults to 'HEAD'.
264
265 '<rev>{caret}@', e.g. 'HEAD{caret}@'::
266 A suffix '{caret}' followed by an at sign is the same as listing
267 all parents of '<rev>' (meaning, include anything reachable from
268 its parents, but not the commit itself).
269
270 '<rev>{caret}!', e.g. 'HEAD{caret}!'::
271 A suffix '{caret}' followed by an exclamation mark is the same
272 as giving commit '<rev>' and then all its parents prefixed with
273 '{caret}' to exclude them (and their ancestors).
274
275 Here are a handful of examples:
276
277 D G H D
278 D F G H I J D F
279 ^G D H D
280 ^D B E I J F B
281 B..C C
282 B...C G H D E B C
283 ^D B C E I J F B C
284 C I J F C
285 C^@ I J F
286 C^! C
287 F^! D G H D F