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     `REBASE_HEAD`, `REVERT_HEAD`, `CHERRY_PICK_HEAD`, `BISECT_HEAD`
  37     and `AUTO_MERGE`);
  38
  39   . otherwise, 'refs/<refname>' if it exists;
  40
  41   . otherwise, 'refs/tags/<refname>' if it exists;
  42
  43   . otherwise, 'refs/heads/<refname>' if it exists;
  44
  45   . otherwise, 'refs/remotes/<refname>' if it exists;
  46
  47   . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
  48
  49 +
  50   `HEAD`:::
  51     names the commit on which you based the changes in the working tree.
  52   `FETCH_HEAD`:::
  53     records the branch which you fetched from a remote repository with
  54     your last `git fetch` invocation.
  55   `ORIG_HEAD`:::
  56     is created by commands that move your `HEAD` in a drastic way (`git
  57     am`, `git merge`, `git rebase`, `git reset`), to record the position
  58     of the `HEAD` before their operation, so that you can easily change
  59     the tip of the branch back to the state before you ran them.
  60   `MERGE_HEAD`:::
  61     records the commit(s) which you are merging into your branch when you
  62     run `git merge`.
  63   `REBASE_HEAD`:::
  64     during a rebase, records the commit at which the operation is
  65     currently stopped, either because of conflicts or an `edit` command in
  66     an interactive rebase.
  67   `REVERT_HEAD`:::
  68     records the commit which you are reverting when you run `git revert`.
  69   `CHERRY_PICK_HEAD`:::
  70     records the commit which you are cherry-picking when you run `git
  71     cherry-pick`.
  72   `BISECT_HEAD`:::
  73     records the current commit to be tested when you run `git bisect
  74     --no-checkout`.
  75   `AUTO_MERGE`:::
  76     records a tree object corresponding to the state the
  77     'ort' merge strategy wrote to the working tree when a merge operation
  78     resulted in conflicts.
  79
  80 +
  81 Note that any of the 'refs/*' cases above may come either from
  82 the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file.
  83 While the ref name encoding is unspecified, UTF-8 is preferred as
  84 some output processing may assume ref names in UTF-8.
  85
  86 '@'::
  87   '@' alone is a shortcut for `HEAD`.
  88
  89 '[<refname>]@{<date>}', e.g. 'master@\{yesterday\}', 'HEAD@{5 minutes ago}'::
  90   A ref followed by the suffix '@' with a date specification
  91   enclosed in a brace
  92   pair (e.g. '\{yesterday\}', '{1 month 2 weeks 3 days 1 hour 1
  93   second ago}' or '{1979-02-26 18:30:00}') specifies the value
  94   of the ref at a prior point in time.  This suffix may only be
  95   used immediately following a ref name and the ref must have an
  96   existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
  97   of your *local* ref at a given time; e.g., what was in your local
  98   'master' branch last week. If you want to look at commits made during
  99   certain times, see `--since` and `--until`.
 100
 101 '<refname>@{<n>}', e.g. 'master@\{1\}'::
 102   A ref followed by the suffix '@' with an ordinal specification
 103   enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
 104   the n-th prior value of that ref.  For example 'master@\{1\}'
 105   is the immediate prior value of 'master' while 'master@\{5\}'
 106   is the 5th prior value of 'master'. This suffix may only be used
 107   immediately following a ref name and the ref must have an existing
 108   log ('$GIT_DIR/logs/<refname>').
 109
 110 '@{<n>}', e.g. '@\{1\}'::
 111   You can use the '@' construct with an empty ref part to get at a
 112   reflog entry of the current branch. For example, if you are on
 113   branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
 114
 115 '@{-<n>}', e.g. '@{-1}'::
 116   The construct '@{-<n>}' means the <n>th branch/commit checked out
 117   before the current one.
 118
 119 '[<branchname>]@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
 120   A branch B may be set up to build on top of a branch X (configured with
 121   `branch.<name>.merge`) at a remote R (configured with
 122   `branch.<name>.remote`). B@{u} refers to the remote-tracking branch for
 123   the branch X taken from remote R, typically found at `refs/remotes/R/X`.
 124
 125 '[<branchname>]@\{push\}', e.g. 'master@\{push\}', '@\{push\}'::
 126   The suffix '@\{push}' reports the branch "where we would push to" if
 127   `git push` were run while `branchname` was checked out (or the current
 128   `HEAD` if no branchname is specified). Like for '@\{upstream\}', we report
 129   the remote-tracking branch that corresponds to that branch at the remote.
 130 +
 131 Here's an example to make it more clear:
 132 +
 133 ------------------------------
 134 $ git config push.default current
 135 $ git config remote.pushdefault myfork
 136 $ git switch -c mybranch origin/master
 137
 138 $ git rev-parse --symbolic-full-name @{upstream}
 139 refs/remotes/origin/master
 140
 141 $ git rev-parse --symbolic-full-name @{push}
 142 refs/remotes/myfork/mybranch
 143 ------------------------------
 144 +
 145 Note in the example that we set up a triangular workflow, where we pull
 146 from one location and push to another. In a non-triangular workflow,
 147 '@\{push}' is the same as '@\{upstream}', and there is no need for it.
 148 +
 149 This suffix is also accepted when spelled in uppercase, and means the same
 150 thing no matter the case.
 151
 152 '<rev>{caret}[<n>]', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
 153   A suffix '{caret}' to a revision parameter means the first parent of
 154   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
 155   '<rev>{caret}'
 156   is equivalent to '<rev>{caret}1').  As a special rule,
 157   '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
 158   object name of a tag object that refers to a commit object.
 159
 160 '<rev>{tilde}[<n>]', e.g. 'HEAD{tilde}, master{tilde}3'::
 161   A suffix '{tilde}' to a revision parameter means the first parent of
 162   that commit object.
 163   A suffix '{tilde}<n>' to a revision parameter means the commit
 164   object that is the <n>th generation ancestor of the named
 165   commit object, following only the first parents.  I.e. '<rev>{tilde}3' is
 166   equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
 167   '<rev>{caret}1{caret}1{caret}1'.  See below for an illustration of
 168   the usage of this form.
 169
 170 '<rev>{caret}{<type>}', e.g. 'v0.99.8{caret}\{commit\}'::
 171   A suffix '{caret}' followed by an object type name enclosed in
 172   brace pair means dereference the object at '<rev>' recursively until
 173   an object of type '<type>' is found or the object cannot be
 174   dereferenced anymore (in which case, barf).
 175   For example, if '<rev>' is a commit-ish, '<rev>{caret}\{commit\}'
 176   describes the corresponding commit object.
 177   Similarly, if '<rev>' is a tree-ish, '<rev>{caret}\{tree\}'
 178   describes the corresponding tree object.
 179   '<rev>{caret}0'
 180   is a short-hand for '<rev>{caret}\{commit\}'.
 181 +
 182 '<rev>{caret}\{object\}' can be used to make sure '<rev>' names an
 183 object that exists, without requiring '<rev>' to be a tag, and
 184 without dereferencing '<rev>'; because a tag is already an object,
 185 it does not have to be dereferenced even once to get to an object.
 186 +
 187 '<rev>{caret}\{tag\}' can be used to ensure that '<rev>' identifies an
 188 existing tag object.
 189
 190 '<rev>{caret}{}', e.g. 'v0.99.8{caret}{}'::
 191   A suffix '{caret}' followed by an empty brace pair
 192   means the object could be a tag,
 193   and dereference the tag recursively until a non-tag object is
 194   found.
 195
 196 '<rev>{caret}{/<text>}', e.g. 'HEAD^{/fix nasty bug}'::
 197   A suffix '{caret}' to a revision parameter, followed by a brace
 198   pair that contains a text led by a slash,
 199   is the same as the ':/fix nasty bug' syntax below except that
 200   it returns the youngest matching commit which is reachable from
 201   the '<rev>' before '{caret}'.
 202
 203 ':/<text>', e.g. ':/fix nasty bug'::
 204   A colon, followed by a slash, followed by a text, names
 205   a commit whose commit message matches the specified regular expression.
 206   This name returns the youngest matching commit which is
 207   reachable from any ref, including HEAD.
 208   The regular expression can match any part of the
 209   commit message. To match messages starting with a string, one can use
 210   e.g. ':/^foo'. The special sequence ':/!' is reserved for modifiers to what
 211   is matched. ':/!-foo' performs a negative match, while ':/!!foo' matches a
 212   literal '!' character, followed by 'foo'. Any other sequence beginning with
 213   ':/!' is reserved for now.
 214   Depending on the given text, the shell's word splitting rules might
 215   require additional quoting.
 216
 217 '<rev>:<path>', e.g. 'HEAD:README', 'master:./README'::
 218   A suffix ':' followed by a path names the blob or tree
 219   at the given path in the tree-ish object named by the part
 220   before the colon.
 221   A path starting with './' or '../' is relative to the current working directory.
 222   The given path will be converted to be relative to the working tree's root directory.
 223   This is most useful to address a blob or tree from a commit or tree that has
 224   the same tree structure as the working tree.
 225
 226 ':[<n>:]<path>', e.g. ':0:README', ':README'::
 227   A colon, optionally followed by a stage number (0 to 3) and a
 228   colon, followed by a path, names a blob object in the
 229   index at the given path. A missing stage number (and the colon
 230   that follows it) names a stage 0 entry. During a merge, stage
 231   1 is the common ancestor, stage 2 is the target branch's version
 232   (typically the current branch), and stage 3 is the version from
 233   the branch which is being merged.
 234
 235 Here is an illustration, by Jon Loeliger.  Both commit nodes B
 236 and C are parents of commit node A.  Parent commits are ordered
 237 left-to-right.
 238
 239 ........................................
 240 G   H   I   J
 241  \ /     \ /
 242   D   E   F
 243    \  |  / \
 244     \ | /   |
 245      \|/    |
 246       B     C
 247        \   /
 248         \ /
 249          A
 250 ........................................
 251
 252     A =      = A^0
 253     B = A^   = A^1     = A~1
 254     C =      = A^2
 255     D = A^^  = A^1^1   = A~2
 256     E = B^2  = A^^2
 257     F = B^3  = A^^3
 258     G = A^^^ = A^1^1^1 = A~3
 259     H = D^2  = B^^2    = A^^^2  = A~2^2
 260     I = F^   = B^3^    = A^^3^
 261     J = F^2  = B^3^2   = A^^3^2
 262
 263
 264 SPECIFYING RANGES
 265 -----------------
 266
 267 History traversing commands such as `git log` operate on a set
 268 of commits, not just a single commit.
 269
 270 For these commands,
 271 specifying a single revision, using the notation described in the
 272 previous section, means the set of commits `reachable` from the given
 273 commit.
 274
 275 Specifying several revisions means the set of commits reachable from
 276 any of the given commits.
 277
 278 A commit's reachable set is the commit itself and the commits in
 279 its ancestry chain.
 280
 281 There are several notations to specify a set of connected commits
 282 (called a "revision range"), illustrated below.
 283
 284
 285 Commit Exclusions
 286 ~~~~~~~~~~~~~~~~~
 287
 288 '{caret}<rev>' (caret) Notation::
 289  To exclude commits reachable from a commit, a prefix '{caret}'
 290  notation is used.  E.g. '{caret}r1 r2' means commits reachable
 291  from 'r2' but exclude the ones reachable from 'r1' (i.e. 'r1' and
 292  its ancestors).
 293
 294 Dotted Range Notations
 295 ~~~~~~~~~~~~~~~~~~~~~~
 296
 297 The '..' (two-dot) Range Notation::
 298  The '{caret}r1 r2' set operation appears so often that there is a shorthand
 299  for it.  When you have two commits 'r1' and 'r2' (named according
 300  to the syntax explained in SPECIFYING REVISIONS above), you can ask
 301  for commits that are reachable from r2 excluding those that are reachable
 302  from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
 303
 304 The '\...' (three-dot) Symmetric Difference Notation::
 305  A similar notation 'r1\...r2' is called symmetric difference
 306  of 'r1' and 'r2' and is defined as
 307  'r1 r2 --not $(git merge-base --all r1 r2)'.
 308  It is the set of commits that are reachable from either one of
 309  'r1' (left side) or 'r2' (right side) but not from both.
 310
 311 In these two shorthand notations, you can omit one end and let it default to HEAD.
 312 For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
 313 did I do since I forked from the origin branch?"  Similarly, '..origin'
 314 is a shorthand for 'HEAD..origin' and asks "What did the origin do since
 315 I forked from them?"  Note that '..' would mean 'HEAD..HEAD' which is an
 316 empty range that is both reachable and unreachable from HEAD.
 317
 318 Commands that are specifically designed to take two distinct ranges
 319 (e.g. "git range-diff R1 R2" to compare two ranges) do exist, but
 320 they are exceptions.  Unless otherwise noted, all "git" commands
 321 that operate on a set of commits work on a single revision range.
 322 In other words, writing two "two-dot range notation" next to each
 323 other, e.g.
 324
 325     $ git log A..B C..D
 326
 327 does *not* specify two revision ranges for most commands.  Instead
 328 it will name a single connected set of commits, i.e. those that are
 329 reachable from either B or D but are reachable from neither A or C.
 330 In a linear history like this:
 331
 332     ---A---B---o---o---C---D
 333
 334 because A and B are reachable from C, the revision range specified
 335 by these two dotted ranges is a single commit D.
 336
 337
 338 Other <rev>{caret} Parent Shorthand Notations
 339 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 340 Three other shorthands exist, particularly useful for merge commits,
 341 for naming a set that is formed by a commit and its parent commits.
 342
 343 The 'r1{caret}@' notation means all parents of 'r1'.
 344
 345 The 'r1{caret}!' notation includes commit 'r1' but excludes all of its parents.
 346 By itself, this notation denotes the single commit 'r1'.
 347
 348 The '<rev>{caret}-[<n>]' notation includes '<rev>' but excludes the <n>th
 349 parent (i.e. a shorthand for '<rev>{caret}<n>..<rev>'), with '<n>' = 1 if
 350 not given. This is typically useful for merge commits where you
 351 can just pass '<commit>{caret}-' to get all the commits in the branch
 352 that was merged in merge commit '<commit>' (including '<commit>'
 353 itself).
 354
 355 While '<rev>{caret}<n>' was about specifying a single commit parent, these
 356 three notations also consider its parents. For example you can say
 357 'HEAD{caret}2{caret}@', however you cannot say 'HEAD{caret}@{caret}2'.
 358
 359 Revision Range Summary
 360 ----------------------
 361
 362 '<rev>'::
 363         Include commits that are reachable from <rev> (i.e. <rev> and its
 364         ancestors).
 365
 366 '{caret}<rev>'::
 367         Exclude commits that are reachable from <rev> (i.e. <rev> and its
 368         ancestors).
 369
 370 '<rev1>..<rev2>'::
 371         Include commits that are reachable from <rev2> but exclude
 372         those that are reachable from <rev1>.  When either <rev1> or
 373         <rev2> is omitted, it defaults to `HEAD`.
 374
 375 '<rev1>\...<rev2>'::
 376         Include commits that are reachable from either <rev1> or
 377         <rev2> but exclude those that are reachable from both.  When
 378         either <rev1> or <rev2> is omitted, it defaults to `HEAD`.
 379
 380 '<rev>{caret}@', e.g. 'HEAD{caret}@'::
 381   A suffix '{caret}' followed by an at sign is the same as listing
 382   all parents of '<rev>' (meaning, include anything reachable from
 383   its parents, but not the commit itself).
 384
 385 '<rev>{caret}!', e.g. 'HEAD{caret}!'::
 386   A suffix '{caret}' followed by an exclamation mark is the same
 387   as giving commit '<rev>' and all its parents prefixed with
 388   '{caret}' to exclude them (and their ancestors).
 389
 390 '<rev>{caret}-<n>', e.g. 'HEAD{caret}-, HEAD{caret}-2'::
 391         Equivalent to '<rev>{caret}<n>..<rev>', with '<n>' = 1 if not
 392         given.
 393
 394 Here are a handful of examples using the Loeliger illustration above,
 395 with each step in the notation's expansion and selection carefully
 396 spelt out:
 397
 398 ....
 399    Args   Expanded arguments    Selected commits
 400    D                            G H D
 401    D F                          G H I J D F
 402    ^G D                         H D
 403    ^D B                         E I J F B
 404    ^D B C                       E I J F B C
 405    C                            I J F C
 406    B..C   = ^B C                C
 407    B...C  = B ^F C              G H D E B C
 408    B^-    = B^..B
 409           = ^B^1 B              E I J F B
 410    C^@    = C^1
 411           = F                   I J F
 412    B^@    = B^1 B^2 B^3
 413           = D E F               D G H E F I J
 414    C^!    = C ^C^@
 415           = C ^C^1
 416           = C ^F                C
 417    B^!    = B ^B^@
 418           = B ^B^1 ^B^2 ^B^3
 419           = B ^D ^E ^F          B
 420    F^! D  = F ^I ^J D           G H D F
 421 ....