Documentation: @{-N} can refer to a commit
[git/git.git] / Documentation / revisions.txt
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1SPECIFYING REVISIONS
2--------------------
3
61e508d9 4A revision parameter '<rev>' typically, but not necessarily, names a
d5fa1f1a 5commit object. It uses what is called an 'extended SHA-1'
5a8f3117 6syntax. Here are various ways to spell object names. The
b62c7697 7ones listed near the end of this list name trees and
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8blobs contained in a commit.
9
61e508d9 10'<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
d5fa1f1a 11 The full SHA-1 object name (40-byte hexadecimal string), or
b62c7697 12 a leading substring that is unique within the repository.
5a8f3117 13 E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
b62c7697 14 name the same commit object if there is no other object in
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15 your repository whose object name starts with dae86e.
16
61e508d9 17'<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
b62c7697 18 Output from `git describe`; i.e. a closest tag, optionally
5a8f3117 19 followed by a dash and a number of commits, followed by a dash, a
83456b13 20 'g', and an abbreviated object name.
5a8f3117 21
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22'<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
23 A symbolic ref name. E.g. 'master' typically means the commit
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24 object referenced by 'refs/heads/master'. If you
25 happen to have both 'heads/master' and 'tags/master', you can
2de9b711 26 explicitly say 'heads/master' to tell Git which one you mean.
89ce391b 27 When ambiguous, a '<refname>' is disambiguated by taking the
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28 first match in the following rules:
29
89ce391b 30 . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
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31 useful only for 'HEAD', 'FETCH_HEAD', 'ORIG_HEAD', 'MERGE_HEAD'
32 and 'CHERRY_PICK_HEAD');
5a8f3117 33
89ce391b 34 . otherwise, 'refs/<refname>' if it exists;
5a8f3117 35
b62c7697 36 . otherwise, 'refs/tags/<refname>' if it exists;
5a8f3117 37
89ce391b 38 . otherwise, 'refs/heads/<refname>' if it exists;
5a8f3117 39
89ce391b 40 . otherwise, 'refs/remotes/<refname>' if it exists;
5a8f3117 41
89ce391b 42 . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
5a8f3117 43+
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44'HEAD' names the commit on which you based the changes in the working tree.
45'FETCH_HEAD' records the branch which you fetched from a remote repository
83456b13 46with your last `git fetch` invocation.
b62c7697 47'ORIG_HEAD' is created by commands that move your 'HEAD' in a drastic
83456b13 48way, to record the position of the 'HEAD' before their operation, so that
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49you can easily change the tip of the branch back to the state before you ran
50them.
51'MERGE_HEAD' records the commit(s) which you are merging into your branch
83456b13 52when you run `git merge`.
b62c7697 53'CHERRY_PICK_HEAD' records the commit which you are cherry-picking
83456b13 54when you run `git cherry-pick`.
5a8f3117 55+
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56Note that any of the 'refs/*' cases above may come either from
57the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
e1c3bf49 58While the ref name encoding is unspecified, UTF-8 is preferred as
1452bd64 59some output processing may assume ref names in UTF-8.
5a8f3117 60
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61'@'::
62 '@' alone is a shortcut for 'HEAD'.
63
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64'<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
65 A ref followed by the suffix '@' with a date specification
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66 enclosed in a brace
67 pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
b62c7697 68 second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
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69 of the ref at a prior point in time. This suffix may only be
70 used immediately following a ref name and the ref must have an
83456b13 71 existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
5a8f3117 72 of your *local* ref at a given time; e.g., what was in your local
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73 'master' branch last week. If you want to look at commits made during
74 certain times, see '--since' and '--until'.
5a8f3117 75
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76'<refname>@\{<n>\}', e.g. 'master@\{1\}'::
77 A ref followed by the suffix '@' with an ordinal specification
b62c7697 78 enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
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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
61e508d9 83 log ('$GIT_DIR/logs/<refname>').
5a8f3117 84
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85'@\{<n>\}', e.g. '@\{1\}'::
86 You can use the '@' construct with an empty ref part to get at a
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87 reflog entry of the current branch. For example, if you are on
88 branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
5a8f3117 89
61e508d9 90'@\{-<n>\}', e.g. '@\{-1\}'::
75d6e552 91 The construct '@\{-<n>\}' means the <n>th branch/commit checked out
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92 before the current one.
93
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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.
5a8f3117 98
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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
5a8f3117 101 that commit object. '{caret}<n>' means the <n>th parent (i.e.
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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
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105 object name of a tag object that refers to a commit object.
106
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107'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
108 A suffix '{tilde}<n>' to a revision parameter means the commit
70eb1307 109 object that is the <n>th generation ancestor of the named
b62c7697 110 commit object, following only the first parents. I.e. '<rev>{tilde}3' is
61e508d9 111 equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
b62c7697 112 '<rev>{caret}1{caret}1{caret}1'. See below for an illustration of
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113 the usage of this form.
114
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115'<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
116 A suffix '{caret}' followed by an object type name enclosed in
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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'
b62c7697 125 is a short-hand for '<rev>{caret}\{commit\}'.
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126+
127'rev{caret}\{object\}' can be used to make sure 'rev' names an
128object that exists, without requiring 'rev' to be a tag, and
129without dereferencing 'rev'; because a tag is already an object,
130it does not have to be dereferenced even once to get to an object.
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131+
132'rev{caret}\{tag\}' can be used to ensure that 'rev' identifies an
133existing tag object.
5a8f3117 134
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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,
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138 and dereference the tag recursively until a non-tag object is
139 found.
140
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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,
b62c7697 144 is the same as the ':/fix nasty bug' syntax below except that
32574b68 145 it returns the youngest matching commit which is reachable from
61e508d9 146 the '<rev>' before '{caret}'.
32574b68 147
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148':/<text>', e.g. ':/fix nasty bug'::
149 A colon, followed by a slash, followed by a text, names
95ad6d2d 150 a commit whose commit message matches the specified regular expression.
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151 This name returns the youngest matching commit which is
152 reachable from any ref. If the commit message starts with a
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153 '!' you have to repeat that; the special sequence ':/!',
154 followed by something else than '!', is reserved for now.
95ad6d2d 155 The regular expression can match any part of the commit message. To
83456b13 156 match messages starting with a string, one can use e.g. ':/^foo'.
5a8f3117 157
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158'<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
159 A suffix ':' followed by a path names the blob or tree
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160 at the given path in the tree-ish object named by the part
161 before the colon.
61e508d9 162 ':path' (with an empty part before the colon)
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163 is a special case of the syntax described next: content
164 recorded in the index at the given path.
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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.
979f7929 167 This is most useful to address a blob or tree from a commit or tree that has
b62c7697 168 the same tree structure as the working tree.
5a8f3117 169
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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
b62c7697 173 index at the given path. A missing stage number (and the colon
61e508d9 174 that follows it) names a stage 0 entry. During a merge, stage
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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
b62c7697 177 the branch which is being merged.
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178
179Here is an illustration, by Jon Loeliger. Both commit nodes B
180and C are parents of commit node A. Parent commits are ordered
181left-to-right.
182
183........................................
184G 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
208SPECIFYING RANGES
209-----------------
210
83456b13 211History traversing commands such as `git log` operate on a set
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212of commits, not just a single commit. To these commands,
213specifying a single revision with the notation described in the
214previous section means the set of commits reachable from that
215commit, following the commit ancestry chain.
216
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217To exclude commits reachable from a commit, a prefix '{caret}'
218notation is used. E.g. '{caret}r1 r2' means commits reachable
219from 'r2' but exclude the ones reachable from 'r1'.
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220
221This set operation appears so often that there is a shorthand
83456b13 222for it. When you have two commits 'r1' and 'r2' (named according
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223to the syntax explained in SPECIFYING REVISIONS above), you can ask
224for commits that are reachable from r2 excluding those that are reachable
83456b13 225from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
5a8f3117 226
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227A similar notation 'r1\...r2' is called symmetric difference
228of 'r1' and 'r2' and is defined as
229'r1 r2 --not $(git merge-base --all r1 r2)'.
5a8f3117 230It is the set of commits that are reachable from either one of
83456b13 231'r1' or 'r2' but not from both.
5a8f3117 232
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233In these two shorthands, you can omit one end and let it default to HEAD.
234For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
235did I do since I forked from the origin branch?" Similarly, '..origin'
236is a shorthand for 'HEAD..origin' and asks "What did the origin do since
237I forked from them?" Note that '..' would mean 'HEAD..HEAD' which is an
238empty range that is both reachable and unreachable from HEAD.
239
5a8f3117 240Two other shorthands for naming a set that is formed by a commit
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241and its parent commits exist. The 'r1{caret}@' notation means all
242parents of 'r1'. 'r1{caret}!' includes commit 'r1' but excludes
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243all of its parents.
244
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245To 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
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257 those that are reachable from <rev1>. When either <rev1> or
258 <rev2> is omitted, it defaults to 'HEAD'.
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259
260'<rev1>\...<rev2>'::
261 Include commits that are reachable from either <rev1> or
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262 <rev2> but exclude those that are reachable from both. When
263 either <rev1> or <rev2> is omitted, it defaults to 'HEAD'.
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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
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275Here 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
ca5ee2d1 281 B..C C
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282 B...C G H D E B C
283 ^D B C E I J F B C
ca5ee2d1 284 C I J F C
5a8f3117 285 C^@ I J F
ca5ee2d1 286 C^! C
5a8f3117 287 F^! D G H D F