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 NOTE: This document shows the "raw" syntax as seen by git. The shell
  11 and other UIs might require additional quoting to protect special
  12 characters and to avoid word splitting.
  13
  14 '<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
  15   The full SHA-1 object name (40-byte hexadecimal string), or
  16   a leading substring that is unique within the repository.
  17   E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
  18   name the same commit object if there is no other object in
  19   your repository whose object name starts with dae86e.
  20
  21 '<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
  22   Output from `git describe`; i.e. a closest tag, optionally
  23   followed by a dash and a number of commits, followed by a dash, a
  24   'g', and an abbreviated object name.
  25
  26 '<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
  27   A symbolic ref name.  E.g. 'master' typically means the commit
  28   object referenced by 'refs/heads/master'.  If you
  29   happen to have both 'heads/master' and 'tags/master', you can
  30   explicitly say 'heads/master' to tell Git which one you mean.
  31   When ambiguous, a '<refname>' is disambiguated by taking the
  32   first match in the following rules:
  33
  34   . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
  35     useful only for `HEAD`, `FETCH_HEAD`, `ORIG_HEAD`, `MERGE_HEAD`
  36     and `CHERRY_PICK_HEAD`);
  37
  38   . otherwise, 'refs/<refname>' if it exists;
  39
  40   . otherwise, 'refs/tags/<refname>' if it exists;
  41
  42   . otherwise, 'refs/heads/<refname>' if it exists;
  43
  44   . otherwise, 'refs/remotes/<refname>' if it exists;
  45
  46   . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
  47 +
  48 `HEAD` names the commit on which you based the changes in the working tree.
  49 `FETCH_HEAD` records the branch which you fetched from a remote repository
  50 with your last `git fetch` invocation.
  51 `ORIG_HEAD` is created by commands that move your `HEAD` in a drastic
  52 way, to record the position of the `HEAD` before their operation, so that
  53 you can easily change the tip of the branch back to the state before you ran
  54 them.
  55 `MERGE_HEAD` records the commit(s) which you are merging into your branch
  56 when you run `git merge`.
  57 `CHERRY_PICK_HEAD` records the commit which you are cherry-picking
  58 when you run `git cherry-pick`.
  59 +
  60 Note that any of the 'refs/*' cases above may come either from
  61 the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file.
  62 While the ref name encoding is unspecified, UTF-8 is preferred as
  63 some output processing may assume ref names in UTF-8.
  64
  65 '@'::
  66   '@' alone is a shortcut for `HEAD`.
  67
  68 '[<refname>]@{<date>}', e.g. 'master@\{yesterday\}', 'HEAD@{5 minutes ago}'::
  69   A ref followed by the suffix '@' with a date specification
  70   enclosed in a brace
  71   pair (e.g. '\{yesterday\}', '{1 month 2 weeks 3 days 1 hour 1
  72   second ago}' or '{1979-02-26 18:30:00}') specifies the value
  73   of the ref at a prior point in time.  This suffix may only be
  74   used immediately following a ref name and the ref must have an
  75   existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
  76   of your *local* ref at a given time; e.g., what was in your local
  77   'master' branch last week. If you want to look at commits made during
  78   certain times, see `--since` and `--until`.
  79
  80 '<refname>@{<n>}', e.g. 'master@\{1\}'::
  81   A ref followed by the suffix '@' with an ordinal specification
  82   enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
  83   the n-th prior value of that ref.  For example 'master@\{1\}'
  84   is the immediate prior value of 'master' while 'master@\{5\}'
  85   is the 5th prior value of 'master'. This suffix may only be used
  86   immediately following a ref name and the ref must have an existing
  87   log ('$GIT_DIR/logs/<refname>').
  88
  89 '@{<n>}', e.g. '@\{1\}'::
  90   You can use the '@' construct with an empty ref part to get at a
  91   reflog entry of the current branch. For example, if you are on
  92   branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
  93
  94 '@{-<n>}', e.g. '@{-1}'::
  95   The construct '@{-<n>}' means the <n>th branch/commit checked out
  96   before the current one.
  97
  98 '[<branchname>]@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
  99   A branch B may be set up to build on top of a branch X (configured with
 100   `branch.<name>.merge`) at a remote R (configured with
 101   `branch.<name>.remote`). B@{u} refers to the remote-tracking branch for
 102   the branch X taken from remote R, typically found at `refs/remotes/R/X`.
 103
 104 '[<branchname>]@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
 105   The suffix '@\{push}' reports the branch "where we would push to" if
 106   `git push` were run while `branchname` was checked out (or the current
 107   `HEAD` if no branchname is specified). Like for '@\{upstream\}', we report
 108   the remote-tracking branch that corresponds to that branch at the remote.
 109 +
 110 Here's an example to make it more clear:
 111 +
 112 ------------------------------
 113 $ git config push.default current
 114 $ git config remote.pushdefault myfork
 115 $ git switch -c mybranch origin/master
 116
 117 $ git rev-parse --symbolic-full-name @{upstream}
 118 refs/remotes/origin/master
 119
 120 $ git rev-parse --symbolic-full-name @{push}
 121 refs/remotes/myfork/mybranch
 122 ------------------------------
 123 +
 124 Note in the example that we set up a triangular workflow, where we pull
 125 from one location and push to another. In a non-triangular workflow,
 126 '@\{push}' is the same as '@\{upstream}', and there is no need for it.
 127 +
 128 This suffix is also accepted when spelled in uppercase, and means the same
 129 thing no matter the case.
 130
 131 '<rev>{caret}[<n>]', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
 132   A suffix '{caret}' to a revision parameter means the first parent of
 133   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
 134   '<rev>{caret}'
 135   is equivalent to '<rev>{caret}1').  As a special rule,
 136   '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
 137   object name of a tag object that refers to a commit object.
 138
 139 '<rev>{tilde}[<n>]', e.g. 'HEAD{tilde}, master{tilde}3'::
 140   A suffix '{tilde}' to a revision parameter means the first parent of
 141   that commit object.
 142   A suffix '{tilde}<n>' to a revision parameter means the commit
 143   object that is the <n>th generation ancestor of the named
 144   commit object, following only the first parents.  I.e. '<rev>{tilde}3' is
 145   equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
 146   '<rev>{caret}1{caret}1{caret}1'.  See below for an illustration of
 147   the usage of this form.
 148
 149 '<rev>{caret}{<type>}', e.g. 'v0.99.8{caret}\{commit\}'::
 150   A suffix '{caret}' followed by an object type name enclosed in
 151   brace pair means dereference the object at '<rev>' recursively until
 152   an object of type '<type>' is found or the object cannot be
 153   dereferenced anymore (in which case, barf).
 154   For example, if '<rev>' is a commit-ish, '<rev>{caret}\{commit\}'
 155   describes the corresponding commit object.
 156   Similarly, if '<rev>' is a tree-ish, '<rev>{caret}\{tree\}'
 157   describes the corresponding tree object.
 158   '<rev>{caret}0'
 159   is a short-hand for '<rev>{caret}\{commit\}'.
 160 +
 161 '<rev>{caret}\{object\}' can be used to make sure '<rev>' names an
 162 object that exists, without requiring '<rev>' to be a tag, and
 163 without dereferencing '<rev>'; because a tag is already an object,
 164 it does not have to be dereferenced even once to get to an object.
 165 +
 166 '<rev>{caret}\{tag\}' can be used to ensure that '<rev>' identifies an
 167 existing tag object.
 168
 169 '<rev>{caret}{}', e.g. 'v0.99.8{caret}{}'::
 170   A suffix '{caret}' followed by an empty brace pair
 171   means the object could be a tag,
 172   and dereference the tag recursively until a non-tag object is
 173   found.
 174
 175 '<rev>{caret}{/<text>}', e.g. 'HEAD^{/fix nasty bug}'::
 176   A suffix '{caret}' to a revision parameter, followed by a brace
 177   pair that contains a text led by a slash,
 178   is the same as the ':/fix nasty bug' syntax below except that
 179   it returns the youngest matching commit which is reachable from
 180   the '<rev>' before '{caret}'.
 181
 182 ':/<text>', e.g. ':/fix nasty bug'::
 183   A colon, followed by a slash, followed by a text, names
 184   a commit whose commit message matches the specified regular expression.
 185   This name returns the youngest matching commit which is
 186   reachable from any ref, including HEAD.
 187   The regular expression can match any part of the
 188   commit message. To match messages starting with a string, one can use
 189   e.g. ':/^foo'. The special sequence ':/!' is reserved for modifiers to what
 190   is matched. ':/!-foo' performs a negative match, while ':/!!foo' matches a
 191   literal '!' character, followed by 'foo'. Any other sequence beginning with
 192   ':/!' is reserved for now.
 193   Depending on the given text, the shell's word splitting rules might
 194   require additional quoting.
 195
 196 '<rev>:<path>', e.g. 'HEAD:README', 'master:./README'::
 197   A suffix ':' followed by a path names the blob or tree
 198   at the given path in the tree-ish object named by the part
 199   before the colon.
 200   A path starting with './' or '../' is relative to the current working directory.
 201   The given path will be converted to be relative to the working tree's root directory.
 202   This is most useful to address a blob or tree from a commit or tree that has
 203   the same tree structure as the working tree.
 204
 205 ':[<n>:]<path>', e.g. ':0:README', ':README'::
 206   A colon, optionally followed by a stage number (0 to 3) and a
 207   colon, followed by a path, names a blob object in the
 208   index at the given path. A missing stage number (and the colon
 209   that follows it) names a stage 0 entry. During a merge, stage
 210   1 is the common ancestor, stage 2 is the target branch's version
 211   (typically the current branch), and stage 3 is the version from
 212   the branch which is being merged.
 213
 214 Here is an illustration, by Jon Loeliger.  Both commit nodes B
 215 and C are parents of commit node A.  Parent commits are ordered
 216 left-to-right.
 217
 218 ........................................
 219 G   H   I   J
 220  \ /     \ /
 221   D   E   F
 222    \  |  / \
 223     \ | /   |
 224      \|/    |
 225       B     C
 226        \   /
 227         \ /
 228          A
 229 ........................................
 230
 231     A =      = A^0
 232     B = A^   = A^1     = A~1
 233     C =      = A^2
 234     D = A^^  = A^1^1   = A~2
 235     E = B^2  = A^^2
 236     F = B^3  = A^^3
 237     G = A^^^ = A^1^1^1 = A~3
 238     H = D^2  = B^^2    = A^^^2  = A~2^2
 239     I = F^   = B^3^    = A^^3^
 240     J = F^2  = B^3^2   = A^^3^2
 241
 242
 243 SPECIFYING RANGES
 244 -----------------
 245
 246 History traversing commands such as `git log` operate on a set
 247 of commits, not just a single commit.
 248
 249 For these commands,
 250 specifying a single revision, using the notation described in the
 251 previous section, means the set of commits `reachable` from the given
 252 commit.
 253
 254 Specifying several revisions means the set of commits reachable from
 255 any of the given commits.
 256
 257 A commit's reachable set is the commit itself and the commits in
 258 its ancestry chain.
 259
 260 There are several notations to specify a set of connected commits
 261 (called a "revision range"), illustrated below.
 262
 263
 264 Commit Exclusions
 265 ~~~~~~~~~~~~~~~~~
 266
 267 '{caret}<rev>' (caret) Notation::
 268  To exclude commits reachable from a commit, a prefix '{caret}'
 269  notation is used.  E.g. '{caret}r1 r2' means commits reachable
 270  from 'r2' but exclude the ones reachable from 'r1' (i.e. 'r1' and
 271  its ancestors).
 272
 273 Dotted Range Notations
 274 ~~~~~~~~~~~~~~~~~~~~~~
 275
 276 The '..' (two-dot) Range Notation::
 277  The '{caret}r1 r2' set operation appears so often that there is a shorthand
 278  for it.  When you have two commits 'r1' and 'r2' (named according
 279  to the syntax explained in SPECIFYING REVISIONS above), you can ask
 280  for commits that are reachable from r2 excluding those that are reachable
 281  from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
 282
 283 The '\...' (three-dot) Symmetric Difference Notation::
 284  A similar notation 'r1\...r2' is called symmetric difference
 285  of 'r1' and 'r2' and is defined as
 286  'r1 r2 --not $(git merge-base --all r1 r2)'.
 287  It is the set of commits that are reachable from either one of
 288  'r1' (left side) or 'r2' (right side) but not from both.
 289
 290 In these two shorthand notations, you can omit one end and let it default to HEAD.
 291 For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
 292 did I do since I forked from the origin branch?"  Similarly, '..origin'
 293 is a shorthand for 'HEAD..origin' and asks "What did the origin do since
 294 I forked from them?"  Note that '..' would mean 'HEAD..HEAD' which is an
 295 empty range that is both reachable and unreachable from HEAD.
 296
 297 Commands that are specifically designed to take two distinct ranges
 298 (e.g. "git range-diff R1 R2" to compare two ranges) do exist, but
 299 they are exceptions.  Unless otherwise noted, all "git" commands
 300 that operate on a set of commits work on a single revision range.
 301 In other words, writing two "two-dot range notation" next to each
 302 other, e.g.
 303
 304     $ git log A..B C..D
 305
 306 does *not* specify two revision ranges for most commands.  Instead
 307 it will name a single connected set of commits, i.e. those that are
 308 reachable from either B or D but are reachable from neither A or C.
 309 In a linear history like this:
 310
 311     ---A---B---o---o---C---D
 312
 313 because A and B are reachable from C, the revision range specified
 314 by these two dotted ranges is a single commit D.
 315
 316
 317 Other <rev>{caret} Parent Shorthand Notations
 318 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 319 Three other shorthands exist, particularly useful for merge commits,
 320 for naming a set that is formed by a commit and its parent commits.
 321
 322 The 'r1{caret}@' notation means all parents of 'r1'.
 323
 324 The 'r1{caret}!' notation includes commit 'r1' but excludes all of its parents.
 325 By itself, this notation denotes the single commit 'r1'.
 326
 327 The '<rev>{caret}-[<n>]' notation includes '<rev>' but excludes the <n>th
 328 parent (i.e. a shorthand for '<rev>{caret}<n>..<rev>'), with '<n>' = 1 if
 329 not given. This is typically useful for merge commits where you
 330 can just pass '<commit>{caret}-' to get all the commits in the branch
 331 that was merged in merge commit '<commit>' (including '<commit>'
 332 itself).
 333
 334 While '<rev>{caret}<n>' was about specifying a single commit parent, these
 335 three notations also consider its parents. For example you can say
 336 'HEAD{caret}2{caret}@', however you cannot say 'HEAD{caret}@{caret}2'.
 337
 338 Revision Range Summary
 339 ----------------------
 340
 341 '<rev>'::
 342         Include commits that are reachable from <rev> (i.e. <rev> and its
 343         ancestors).
 344
 345 '{caret}<rev>'::
 346         Exclude commits that are reachable from <rev> (i.e. <rev> and its
 347         ancestors).
 348
 349 '<rev1>..<rev2>'::
 350         Include commits that are reachable from <rev2> but exclude
 351         those that are reachable from <rev1>.  When either <rev1> or
 352         <rev2> is omitted, it defaults to `HEAD`.
 353
 354 '<rev1>\...<rev2>'::
 355         Include commits that are reachable from either <rev1> or
 356         <rev2> but exclude those that are reachable from both.  When
 357         either <rev1> or <rev2> is omitted, it defaults to `HEAD`.
 358
 359 '<rev>{caret}@', e.g. 'HEAD{caret}@'::
 360   A suffix '{caret}' followed by an at sign is the same as listing
 361   all parents of '<rev>' (meaning, include anything reachable from
 362   its parents, but not the commit itself).
 363
 364 '<rev>{caret}!', e.g. 'HEAD{caret}!'::
 365   A suffix '{caret}' followed by an exclamation mark is the same
 366   as giving commit '<rev>' and then all its parents prefixed with
 367   '{caret}' to exclude them (and their ancestors).
 368
 369 '<rev>{caret}-<n>', e.g. 'HEAD{caret}-, HEAD{caret}-2'::
 370         Equivalent to '<rev>{caret}<n>..<rev>', with '<n>' = 1 if not
 371         given.
 372
 373 Here are a handful of examples using the Loeliger illustration above,
 374 with each step in the notation's expansion and selection carefully
 375 spelt out:
 376
 377 ....
 378    Args   Expanded arguments    Selected commits
 379    D                            G H D
 380    D F                          G H I J D F
 381    ^G D                         H D
 382    ^D B                         E I J F B
 383    ^D B C                       E I J F B C
 384    C                            I J F C
 385    B..C   = ^B C                C
 386    B...C  = B ^F C              G H D E B C
 387    B^-    = B^..B
 388           = ^B^1 B              E I J F B
 389    C^@    = C^1
 390           = F                   I J F
 391    B^@    = B^1 B^2 B^3
 392           = D E F               D G H E F I J
 393    C^!    = C ^C^@
 394           = C ^C^1
 395           = C ^F                C
 396    B^!    = B ^B^@
 397           = B ^B^1 ^B^2 ^B^3
 398           = B ^D ^E ^F          B
 399    F^! D  = F ^I ^J D           G H D F
 400 ....