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 '<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
  11   The full SHA-1 object name (40-byte hexadecimal string), or
  12   a leading substring that is unique within the repository.
  13   E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
  14   name the same commit object if there is no other object in
  15   your repository whose object name starts with dae86e.
  16
  17 '<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
  18   Output from `git describe`; i.e. a closest tag, optionally
  19   followed by a dash and a number of commits, followed by a dash, a
  20   'g', and an abbreviated object name.
  21
  22 '<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
  23   A symbolic ref name.  E.g. 'master' typically means the commit
  24   object referenced by 'refs/heads/master'.  If you
  25   happen to have both 'heads/master' and 'tags/master', you can
  26   explicitly say 'heads/master' to tell Git which one you mean.
  27   When ambiguous, a '<refname>' is disambiguated by taking the
  28   first match in the following rules:
  29
  30   . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
  31     useful only for 'HEAD', 'FETCH_HEAD', 'ORIG_HEAD', 'MERGE_HEAD'
  32     and 'CHERRY_PICK_HEAD');
  33
  34   . otherwise, 'refs/<refname>' if it exists;
  35
  36   . otherwise, 'refs/tags/<refname>' if it exists;
  37
  38   . otherwise, 'refs/heads/<refname>' if it exists;
  39
  40   . otherwise, 'refs/remotes/<refname>' if it exists;
  41
  42   . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
  43 +
  44 'HEAD' names the commit on which you based the changes in the working tree.
  45 'FETCH_HEAD' records the branch which you fetched from a remote repository
  46 with your last `git fetch` invocation.
  47 'ORIG_HEAD' is created by commands that move your 'HEAD' in a drastic
  48 way, to record the position of the 'HEAD' before their operation, so that
  49 you can easily change the tip of the branch back to the state before you ran
  50 them.
  51 'MERGE_HEAD' records the commit(s) which you are merging into your branch
  52 when you run `git merge`.
  53 'CHERRY_PICK_HEAD' records the commit which you are cherry-picking
  54 when you run `git cherry-pick`.
  55 +
  56 Note that any of the 'refs/*' cases above may come either from
  57 the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
  58 While the ref name encoding is unspecified, UTF-8 is preferred as
  59 some output processing may assume ref names in UTF-8.
  60
  61 '<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
  62   A ref followed by the suffix '@' with a date specification
  63   enclosed in a brace
  64   pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
  65   second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
  66   of the ref at a prior point in time.  This suffix may only be
  67   used immediately following a ref name and the ref must have an
  68   existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
  69   of your *local* ref at a given time; e.g., what was in your local
  70   'master' branch last week. If you want to look at commits made during
  71   certain times, see '--since' and '--until'.
  72
  73 '<refname>@\{<n>\}', e.g. 'master@\{1\}'::
  74   A ref followed by the suffix '@' with an ordinal specification
  75   enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
  76   the n-th prior value of that ref.  For example 'master@\{1\}'
  77   is the immediate prior value of 'master' while 'master@\{5\}'
  78   is the 5th prior value of 'master'. This suffix may only be used
  79   immediately following a ref name and the ref must have an existing
  80   log ('$GIT_DIR/logs/<refname>').
  81
  82 '@\{<n>\}', e.g. '@\{1\}'::
  83   You can use the '@' construct with an empty ref part to get at a
  84   reflog entry of the current branch. For example, if you are on
  85   branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
  86
  87 '@\{-<n>\}', e.g. '@\{-1\}'::
  88   The construct '@\{-<n>\}' means the <n>th branch checked out
  89   before the current one.
  90
  91 '<branchname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
  92   The suffix '@\{upstream\}' to a branchname (short form '<branchname>@\{u\}')
  93   refers to the branch that the branch specified by branchname is set to build on
  94   top of.  A missing branchname defaults to the current one.
  95
  96 '<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
  97   A suffix '{caret}' to a revision parameter means the first parent of
  98   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
  99   '<rev>{caret}'
 100   is equivalent to '<rev>{caret}1').  As a special rule,
 101   '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
 102   object name of a tag object that refers to a commit object.
 103
 104 '<rev>{tilde}<n>', e.g. 'master{tilde}3'::
 105   A suffix '{tilde}<n>' to a revision parameter means the commit
 106   object that is the <n>th generation ancestor of the named
 107   commit object, following only the first parents.  I.e. '<rev>{tilde}3' is
 108   equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
 109   '<rev>{caret}1{caret}1{caret}1'.  See below for an illustration of
 110   the usage of this form.
 111
 112 '<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
 113   A suffix '{caret}' followed by an object type name enclosed in
 114   brace pair means the object
 115   could be a tag, and dereference the tag recursively until an
 116   object of that type is found or the object cannot be
 117   dereferenced anymore (in which case, barf).  '<rev>{caret}0'
 118   is a short-hand for '<rev>{caret}\{commit\}'.
 119
 120 '<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
 121   A suffix '{caret}' followed by an empty brace pair
 122   means the object could be a tag,
 123   and dereference the tag recursively until a non-tag object is
 124   found.
 125
 126 '<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
 127   A suffix '{caret}' to a revision parameter, followed by a brace
 128   pair that contains a text led by a slash,
 129   is the same as the ':/fix nasty bug' syntax below except that
 130   it returns the youngest matching commit which is reachable from
 131   the '<rev>' before '{caret}'.
 132
 133 ':/<text>', e.g. ':/fix nasty bug'::
 134   A colon, followed by a slash, followed by a text, names
 135   a commit whose commit message matches the specified regular expression.
 136   This name returns the youngest matching commit which is
 137   reachable from any ref.  If the commit message starts with a
 138   '!' you have to repeat that;  the special sequence ':/!',
 139   followed by something else than '!', is reserved for now.
 140   The regular expression can match any part of the commit message. To
 141   match messages starting with a string, one can use e.g. ':/^foo'.
 142
 143 '<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
 144   A suffix ':' followed by a path names the blob or tree
 145   at the given path in the tree-ish object named by the part
 146   before the colon.
 147   ':path' (with an empty part before the colon)
 148   is a special case of the syntax described next: content
 149   recorded in the index at the given path.
 150   A path starting with './' or '../' is relative to the current working directory.
 151   The given path will be converted to be relative to the working tree's root directory.
 152   This is most useful to address a blob or tree from a commit or tree that has
 153   the same tree structure as the working tree.
 154
 155 ':<n>:<path>', e.g. ':0:README', ':README'::
 156   A colon, optionally followed by a stage number (0 to 3) and a
 157   colon, followed by a path, names a blob object in the
 158   index at the given path. A missing stage number (and the colon
 159   that follows it) names a stage 0 entry. During a merge, stage
 160   1 is the common ancestor, stage 2 is the target branch's version
 161   (typically the current branch), and stage 3 is the version from
 162   the branch which is being merged.
 163
 164 Here is an illustration, by Jon Loeliger.  Both commit nodes B
 165 and C are parents of commit node A.  Parent commits are ordered
 166 left-to-right.
 167
 168 ........................................
 169 G   H   I   J
 170  \ /     \ /
 171   D   E   F
 172    \  |  / \
 173     \ | /   |
 174      \|/    |
 175       B     C
 176        \   /
 177         \ /
 178          A
 179 ........................................
 180
 181     A =      = A^0
 182     B = A^   = A^1     = A~1
 183     C = A^2  = A^2
 184     D = A^^  = A^1^1   = A~2
 185     E = B^2  = A^^2
 186     F = B^3  = A^^3
 187     G = A^^^ = A^1^1^1 = A~3
 188     H = D^2  = B^^2    = A^^^2  = A~2^2
 189     I = F^   = B^3^    = A^^3^
 190     J = F^2  = B^3^2   = A^^3^2
 191
 192
 193 SPECIFYING RANGES
 194 -----------------
 195
 196 History traversing commands such as `git log` operate on a set
 197 of commits, not just a single commit.  To these commands,
 198 specifying a single revision with the notation described in the
 199 previous section means the set of commits reachable from that
 200 commit, following the commit ancestry chain.
 201
 202 To exclude commits reachable from a commit, a prefix '{caret}'
 203 notation is used.  E.g. '{caret}r1 r2' means commits reachable
 204 from 'r2' but exclude the ones reachable from 'r1'.
 205
 206 This set operation appears so often that there is a shorthand
 207 for it.  When you have two commits 'r1' and 'r2' (named according
 208 to the syntax explained in SPECIFYING REVISIONS above), you can ask
 209 for commits that are reachable from r2 excluding those that are reachable
 210 from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
 211
 212 A similar notation 'r1\...r2' is called symmetric difference
 213 of 'r1' and 'r2' and is defined as
 214 'r1 r2 --not $(git merge-base --all r1 r2)'.
 215 It is the set of commits that are reachable from either one of
 216 'r1' or 'r2' but not from both.
 217
 218 In these two shorthands, you can omit one end and let it default to HEAD.
 219 For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
 220 did I do since I forked from the origin branch?"  Similarly, '..origin'
 221 is a shorthand for 'HEAD..origin' and asks "What did the origin do since
 222 I forked from them?"  Note that '..' would mean 'HEAD..HEAD' which is an
 223 empty range that is both reachable and unreachable from HEAD.
 224
 225 Two other shorthands for naming a set that is formed by a commit
 226 and its parent commits exist.  The 'r1{caret}@' notation means all
 227 parents of 'r1'.  'r1{caret}!' includes commit 'r1' but excludes
 228 all of its parents.
 229
 230 To summarize:
 231
 232 '<rev>'::
 233         Include commits that are reachable from (i.e. ancestors of)
 234         <rev>.
 235
 236 '{caret}<rev>'::
 237         Exclude commits that are reachable from (i.e. ancestors of)
 238         <rev>.
 239
 240 '<rev1>..<rev2>'::
 241         Include commits that are reachable from <rev2> but exclude
 242         those that are reachable from <rev1>.
 243
 244 '<rev1>\...<rev2>'::
 245         Include commits that are reachable from either <rev1> or
 246         <rev2> but exclude those that are reachable from both.
 247
 248 '<rev>{caret}@', e.g. 'HEAD{caret}@'::
 249   A suffix '{caret}' followed by an at sign is the same as listing
 250   all parents of '<rev>' (meaning, include anything reachable from
 251   its parents, but not the commit itself).
 252
 253 '<rev>{caret}!', e.g. 'HEAD{caret}!'::
 254   A suffix '{caret}' followed by an exclamation mark is the same
 255   as giving commit '<rev>' and then all its parents prefixed with
 256   '{caret}' to exclude them (and their ancestors).
 257
 258 Here are a handful of examples:
 259
 260    D                G H D
 261    D F              G H I J D F
 262    ^G D             H D
 263    ^D B             E I J F B
 264    B..C             C
 265    B...C            G H D E B C
 266    ^D B C           E I J F B C
 267    C                I J F C
 268    C^@              I J F
 269    C^!              C
 270    F^! D            G H D F