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