Add new @ shortcut for HEAD
[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\}'::
b62c7697 91 The construct '@\{-<n>\}' means the <n>th branch 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
117 brace pair means the object
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118 could be a tag, and dereference the tag recursively until an
119 object of that type is found or the object cannot be
61e508d9 120 dereferenced anymore (in which case, barf). '<rev>{caret}0'
b62c7697 121 is a short-hand for '<rev>{caret}\{commit\}'.
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122+
123'rev{caret}\{object\}' can be used to make sure 'rev' names an
124object that exists, without requiring 'rev' to be a tag, and
125without dereferencing 'rev'; because a tag is already an object,
126it does not have to be dereferenced even once to get to an object.
5a8f3117 127
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128'<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
129 A suffix '{caret}' followed by an empty brace pair
130 means the object could be a tag,
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131 and dereference the tag recursively until a non-tag object is
132 found.
133
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134'<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
135 A suffix '{caret}' to a revision parameter, followed by a brace
136 pair that contains a text led by a slash,
b62c7697 137 is the same as the ':/fix nasty bug' syntax below except that
32574b68 138 it returns the youngest matching commit which is reachable from
61e508d9 139 the '<rev>' before '{caret}'.
32574b68 140
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141':/<text>', e.g. ':/fix nasty bug'::
142 A colon, followed by a slash, followed by a text, names
95ad6d2d 143 a commit whose commit message matches the specified regular expression.
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144 This name returns the youngest matching commit which is
145 reachable from any ref. If the commit message starts with a
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146 '!' you have to repeat that; the special sequence ':/!',
147 followed by something else than '!', is reserved for now.
95ad6d2d 148 The regular expression can match any part of the commit message. To
83456b13 149 match messages starting with a string, one can use e.g. ':/^foo'.
5a8f3117 150
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151'<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
152 A suffix ':' followed by a path names the blob or tree
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153 at the given path in the tree-ish object named by the part
154 before the colon.
61e508d9 155 ':path' (with an empty part before the colon)
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156 is a special case of the syntax described next: content
157 recorded in the index at the given path.
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158 A path starting with './' or '../' is relative to the current working directory.
159 The given path will be converted to be relative to the working tree's root directory.
979f7929 160 This is most useful to address a blob or tree from a commit or tree that has
b62c7697 161 the same tree structure as the working tree.
5a8f3117 162
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163':<n>:<path>', e.g. ':0:README', ':README'::
164 A colon, optionally followed by a stage number (0 to 3) and a
165 colon, followed by a path, names a blob object in the
b62c7697 166 index at the given path. A missing stage number (and the colon
61e508d9 167 that follows it) names a stage 0 entry. During a merge, stage
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168 1 is the common ancestor, stage 2 is the target branch's version
169 (typically the current branch), and stage 3 is the version from
b62c7697 170 the branch which is being merged.
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171
172Here is an illustration, by Jon Loeliger. Both commit nodes B
173and C are parents of commit node A. Parent commits are ordered
174left-to-right.
175
176........................................
177G H I J
178 \ / \ /
179 D E F
180 \ | / \
181 \ | / |
182 \|/ |
183 B C
184 \ /
185 \ /
186 A
187........................................
188
189 A = = A^0
190 B = A^ = A^1 = A~1
191 C = A^2 = A^2
192 D = A^^ = A^1^1 = A~2
193 E = B^2 = A^^2
194 F = B^3 = A^^3
195 G = A^^^ = A^1^1^1 = A~3
196 H = D^2 = B^^2 = A^^^2 = A~2^2
197 I = F^ = B^3^ = A^^3^
198 J = F^2 = B^3^2 = A^^3^2
199
200
201SPECIFYING RANGES
202-----------------
203
83456b13 204History traversing commands such as `git log` operate on a set
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205of commits, not just a single commit. To these commands,
206specifying a single revision with the notation described in the
207previous section means the set of commits reachable from that
208commit, following the commit ancestry chain.
209
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210To exclude commits reachable from a commit, a prefix '{caret}'
211notation is used. E.g. '{caret}r1 r2' means commits reachable
212from 'r2' but exclude the ones reachable from 'r1'.
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213
214This set operation appears so often that there is a shorthand
83456b13 215for it. When you have two commits 'r1' and 'r2' (named according
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216to the syntax explained in SPECIFYING REVISIONS above), you can ask
217for commits that are reachable from r2 excluding those that are reachable
83456b13 218from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
5a8f3117 219
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220A similar notation 'r1\...r2' is called symmetric difference
221of 'r1' and 'r2' and is defined as
222'r1 r2 --not $(git merge-base --all r1 r2)'.
5a8f3117 223It is the set of commits that are reachable from either one of
83456b13 224'r1' or 'r2' but not from both.
5a8f3117 225
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226In these two shorthands, you can omit one end and let it default to HEAD.
227For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
228did I do since I forked from the origin branch?" Similarly, '..origin'
229is a shorthand for 'HEAD..origin' and asks "What did the origin do since
230I forked from them?" Note that '..' would mean 'HEAD..HEAD' which is an
231empty range that is both reachable and unreachable from HEAD.
232
5a8f3117 233Two other shorthands for naming a set that is formed by a commit
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234and its parent commits exist. The 'r1{caret}@' notation means all
235parents of 'r1'. 'r1{caret}!' includes commit 'r1' but excludes
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236all of its parents.
237
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238To summarize:
239
240'<rev>'::
241 Include commits that are reachable from (i.e. ancestors of)
242 <rev>.
243
244'{caret}<rev>'::
245 Exclude commits that are reachable from (i.e. ancestors of)
246 <rev>.
247
248'<rev1>..<rev2>'::
249 Include commits that are reachable from <rev2> but exclude
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250 those that are reachable from <rev1>. When either <rev1> or
251 <rev2> is omitted, it defaults to 'HEAD'.
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252
253'<rev1>\...<rev2>'::
254 Include commits that are reachable from either <rev1> or
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255 <rev2> but exclude those that are reachable from both. When
256 either <rev1> or <rev2> is omitted, it defaults to 'HEAD'.
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257
258'<rev>{caret}@', e.g. 'HEAD{caret}@'::
259 A suffix '{caret}' followed by an at sign is the same as listing
260 all parents of '<rev>' (meaning, include anything reachable from
261 its parents, but not the commit itself).
262
263'<rev>{caret}!', e.g. 'HEAD{caret}!'::
264 A suffix '{caret}' followed by an exclamation mark is the same
265 as giving commit '<rev>' and then all its parents prefixed with
266 '{caret}' to exclude them (and their ancestors).
267
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268Here are a handful of examples:
269
270 D G H D
271 D F G H I J D F
272 ^G D H D
273 ^D B E I J F B
ca5ee2d1 274 B..C C
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275 B...C G H D E B C
276 ^D B C E I J F B C
ca5ee2d1 277 C I J F C
5a8f3117 278 C^@ I J F
ca5ee2d1 279 C^! C
5a8f3117 280 F^! D G H D F