Documentation/revisions.txt - jrn/git - Git at Google

 SPECIFYING REVISIONS
 --------------------

 A revision parameter '<rev>' typically, but not necessarily, names a
 commit object.  It uses what is called an 'extended SHA1'
 syntax.  Here are various ways to spell object names.  The
 ones listed near the end of this list name trees and
 blobs contained in a commit.

 '<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
   The full SHA1 object name (40-byte hexadecimal string), or
   a leading substring that is unique within the repository.
   E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
   name the same commit object if there is no other object in
   your repository whose object name starts with dae86e.

 '<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
   Output from `git describe`; i.e. a closest tag, optionally
   followed by a dash and a number of commits, followed by a dash, a
   'g', and an abbreviated object name.

 '<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
   A symbolic ref name.  E.g. 'master' typically means the commit
   object referenced by 'refs/heads/master'.  If you
   happen to have both 'heads/master' and 'tags/master', you can
   explicitly say 'heads/master' to tell git which one you mean.
   When ambiguous, a '<refname>' is disambiguated by taking the
   first match in the following rules:

   . If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
     useful only for 'HEAD', 'FETCH_HEAD', 'ORIG_HEAD', 'MERGE_HEAD'
     and 'CHERRY_PICK_HEAD');

   . otherwise, 'refs/<refname>' if it exists;

   . otherwise, 'refs/tags/<refname>' if it exists;

   . otherwise, 'refs/heads/<refname>' if it exists;

   . otherwise, 'refs/remotes/<refname>' if it exists;

   . otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
 +
 'HEAD' names the commit on which you based the changes in the working tree.
 'FETCH_HEAD' records the branch which you fetched from a remote repository
 with your last `git fetch` invocation.
 'ORIG_HEAD' is created by commands that move your 'HEAD' in a drastic
 way, to record the position of the 'HEAD' before their operation, so that
 you can easily change the tip of the branch back to the state before you ran
 them.
 'MERGE_HEAD' records the commit(s) which you are merging into your branch
 when you run `git merge`.
 'CHERRY_PICK_HEAD' records the commit which you are cherry-picking
 when you run `git cherry-pick`.
 +
 Note that any of the 'refs/*' cases above may come either from
 the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
 While the ref name encoding is unspecified, UTF-8 is prefered as
 some output processing may assume ref names in UTF-8.

 '<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
   A ref followed by the suffix '@' with a date specification
   enclosed in a brace
   pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
   second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
   of the ref at a prior point in time.  This suffix may only be
   used immediately following a ref name and the ref must have an
   existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
   of your *local* ref at a given time; e.g., what was in your local
   'master' branch last week. If you want to look at commits made during
   certain times, see '--since' and '--until'.

 '<refname>@\{<n>\}', e.g. 'master@\{1\}'::
   A ref followed by the suffix '@' with an ordinal specification
   enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
   the n-th prior value of that ref.  For example 'master@\{1\}'
   is the immediate prior value of 'master' while 'master@\{5\}'
   is the 5th prior value of 'master'. This suffix may only be used
   immediately following a ref name and the ref must have an existing
   log ('$GIT_DIR/logs/<refname>').

 '@\{<n>\}', e.g. '@\{1\}'::
   You can use the '@' construct with an empty ref part to get at a
   reflog entry of the current branch. For example, if you are on
   branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.

 '@\{-<n>\}', e.g. '@\{-1\}'::
   The construct '@\{-<n>\}' means the <n>th branch checked out
   before the current one.

 '<refname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
   The suffix '@\{upstream\}' to a ref (short form '<refname>@\{u\}') refers to
   the branch the ref is set to build on top of.  A missing ref defaults
   to the current branch.

 '<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
   A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   '<rev>{caret}'
   is equivalent to '<rev>{caret}1').  As a special rule,
   '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
   object name of a tag object that refers to a commit object.

 '<rev>{tilde}<n>', e.g. 'master{tilde}3'::
   A suffix '{tilde}<n>' to a revision parameter means the commit
   object that is the <n>th generation ancestor of the named
   commit object, following only the first parents.  I.e. '<rev>{tilde}3' is
   equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
   '<rev>{caret}1{caret}1{caret}1'.  See below for an illustration of
   the usage of this form.

 '<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
   A suffix '{caret}' followed by an object type name enclosed in
   brace pair means the object
   could be a tag, and dereference the tag recursively until an
   object of that type is found or the object cannot be
   dereferenced anymore (in which case, barf).  '<rev>{caret}0'
   is a short-hand for '<rev>{caret}\{commit\}'.

 '<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
   A suffix '{caret}' followed by an empty brace pair
   means the object could be a tag,
   and dereference the tag recursively until a non-tag object is
   found.

 '<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
   A suffix '{caret}' to a revision parameter, followed by a brace
   pair that contains a text led by a slash,
   is the same as the ':/fix nasty bug' syntax below except that
   it returns the youngest matching commit which is reachable from
   the '<rev>' before '{caret}'.

 ':/<text>', e.g. ':/fix nasty bug'::
   A colon, followed by a slash, followed by a text, names
   a commit whose commit message matches the specified regular expression.
   This name returns the youngest matching commit which is
   reachable from any ref.  If the commit message starts with a
   '!' you have to repeat that;  the special sequence ':/!',
   followed by something else than '!', is reserved for now.
   The regular expression can match any part of the commit message. To
   match messages starting with a string, one can use e.g. ':/^foo'.

 '<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
   A suffix ':' followed by a path names the blob or tree
   at the given path in the tree-ish object named by the part
   before the colon.
   ':path' (with an empty part before the colon)
   is a special case of the syntax described next: content
   recorded in the index at the given path.
   A path starting with './' or '../' is relative to the current working directory.
   The given path will be converted to be relative to the working tree's root directory.
   This is most useful to address a blob or tree from a commit or tree that has
   the same tree structure as the working tree.

 ':<n>:<path>', e.g. ':0:README', ':README'::
   A colon, optionally followed by a stage number (0 to 3) and a
   colon, followed by a path, names a blob object in the
   index at the given path. A missing stage number (and the colon
   that follows it) names a stage 0 entry. During a merge, stage
   1 is the common ancestor, stage 2 is the target branch's version
   (typically the current branch), and stage 3 is the version from
   the branch which is being merged.

 Here is an illustration, by Jon Loeliger.  Both commit nodes B
 and C are parents of commit node A.  Parent commits are ordered
 left-to-right.

 ........................................
 G   H   I   J
  \ /     \ /
   D   E   F
    \  |  / \
     \ | /   |
      \|/    |
       B     C
        \   /
         \ /
          A
 ........................................

     A =      = A^0
     B = A^   = A^1     = A~1
     C = A^2  = A^2
     D = A^^  = A^1^1   = A~2
     E = B^2  = A^^2
     F = B^3  = A^^3
     G = A^^^ = A^1^1^1 = A~3
     H = D^2  = B^^2    = A^^^2  = A~2^2
     I = F^   = B^3^    = A^^3^
     J = F^2  = B^3^2   = A^^3^2


 SPECIFYING RANGES
 -----------------

 History traversing commands such as `git log` operate on a set
 of commits, not just a single commit.  To these commands,
 specifying a single revision with the notation described in the
 previous section means the set of commits reachable from that
 commit, following the commit ancestry chain.

 To exclude commits reachable from a commit, a prefix '{caret}'
 notation is used.  E.g. '{caret}r1 r2' means commits reachable
 from 'r2' but exclude the ones reachable from 'r1'.

 This set operation appears so often that there is a shorthand
 for it.  When you have two commits 'r1' and 'r2' (named according
 to the syntax explained in SPECIFYING REVISIONS above), you can ask
 for commits that are reachable from r2 excluding those that are reachable
 from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.

 A similar notation 'r1\...r2' is called symmetric difference
 of 'r1' and 'r2' and is defined as
 'r1 r2 --not $(git merge-base --all r1 r2)'.
 It is the set of commits that are reachable from either one of
 'r1' or 'r2' but not from both.

 In these two shorthands, you can omit one end and let it default to HEAD.
 For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
 did I do since I forked from the origin branch?"  Similarly, '..origin'
 is a shorthand for 'HEAD..origin' and asks "What did the origin do since
 I forked from them?"  Note that '..' would mean 'HEAD..HEAD' which is an
 empty range that is both reachable and unreachable from HEAD.

 Two other shorthands for naming a set that is formed by a commit
 and its parent commits exist.  The 'r1{caret}@' notation means all
 parents of 'r1'.  'r1{caret}!' includes commit 'r1' but excludes
 all of its parents.

 To summarize:

 '<rev>'::
 	Include commits that are reachable from (i.e. ancestors of)
 	<rev>.

 '{caret}<rev>'::
 	Exclude commits that are reachable from (i.e. ancestors of)
 	<rev>.

 '<rev1>..<rev2>'::
 	Include commits that are reachable from <rev2> but exclude
 	those that are reachable from <rev1>.

 '<rev1>\...<rev2>'::
 	Include commits that are reachable from either <rev1> or
 	<rev2> but exclude those that are reachable from both.

 '<rev>{caret}@', e.g. 'HEAD{caret}@'::
   A suffix '{caret}' followed by an at sign is the same as listing
   all parents of '<rev>' (meaning, include anything reachable from
   its parents, but not the commit itself).

 '<rev>{caret}!', e.g. 'HEAD{caret}!'::
   A suffix '{caret}' followed by an exclamation mark is the same
   as giving commit '<rev>' and then all its parents prefixed with
   '{caret}' to exclude them (and their ancestors).

 Here are a handful of examples:

    D                G H D
    D F              G H I J D F
    ^G D             H D
    ^D B             E I J F B
    B..C             C
    B...C            G H D E B C
    ^D B C           E I J F B C
    C                I J F C
    C^@              I J F
    C^!              C
    F^! D            G H D F
	SPECIFYING REVISIONS
	--------------------

	A revision parameter '<rev>' typically, but not necessarily, names a
	commit object. It uses what is called an 'extended SHA1'
	syntax. Here are various ways to spell object names. The
	ones listed near the end of this list name trees and
	blobs contained in a commit.

	'<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
	The full SHA1 object name (40-byte hexadecimal string), or
	a leading substring that is unique within the repository.
	E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
	name the same commit object if there is no other object in
	your repository whose object name starts with dae86e.

	'<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
	Output from `git describe`; i.e. a closest tag, optionally
	followed by a dash and a number of commits, followed by a dash, a
	'g', and an abbreviated object name.

	'<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
	A symbolic ref name. E.g. 'master' typically means the commit
	object referenced by 'refs/heads/master'. If you
	happen to have both 'heads/master' and 'tags/master', you can
	explicitly say 'heads/master' to tell git which one you mean.
	When ambiguous, a '<refname>' is disambiguated by taking the
	first match in the following rules:

	. If '$GIT_DIR/<refname>' exists, that is what you mean (this is usually
	useful only for 'HEAD', 'FETCH_HEAD', 'ORIG_HEAD', 'MERGE_HEAD'
	and 'CHERRY_PICK_HEAD');

	. otherwise, 'refs/<refname>' if it exists;

	. otherwise, 'refs/tags/<refname>' if it exists;

	. otherwise, 'refs/heads/<refname>' if it exists;

	. otherwise, 'refs/remotes/<refname>' if it exists;

	. otherwise, 'refs/remotes/<refname>/HEAD' if it exists.
	+
	'HEAD' names the commit on which you based the changes in the working tree.
	'FETCH_HEAD' records the branch which you fetched from a remote repository
	with your last `git fetch` invocation.
	'ORIG_HEAD' is created by commands that move your 'HEAD' in a drastic
	way, to record the position of the 'HEAD' before their operation, so that
	you can easily change the tip of the branch back to the state before you ran
	them.
	'MERGE_HEAD' records the commit(s) which you are merging into your branch
	when you run `git merge`.
	'CHERRY_PICK_HEAD' records the commit which you are cherry-picking
	when you run `git cherry-pick`.
	+
	Note that any of the 'refs/*' cases above may come either from
	the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
	While the ref name encoding is unspecified, UTF-8 is prefered as
	some output processing may assume ref names in UTF-8.

	'<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
	A ref followed by the suffix '@' with a date specification
	enclosed in a brace
	pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
	second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
	of the ref at a prior point in time. This suffix may only be
	used immediately following a ref name and the ref must have an
	existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
	of your local ref at a given time; e.g., what was in your local
	'master' branch last week. If you want to look at commits made during
	certain times, see '--since' and '--until'.

	'<refname>@\{<n>\}', e.g. 'master@\{1\}'::
	A ref followed by the suffix '@' with an ordinal specification
	enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
	the n-th prior value of that ref. For example 'master@\{1\}'
	is the immediate prior value of 'master' while 'master@\{5\}'
	is the 5th prior value of 'master'. This suffix may only be used
	immediately following a ref name and the ref must have an existing
	log ('$GIT_DIR/logs/<refname>').

	'@\{<n>\}', e.g. '@\{1\}'::
	You can use the '@' construct with an empty ref part to get at a
	reflog entry of the current branch. For example, if you are on
	branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.

	'@\{-<n>\}', e.g. '@\{-1\}'::
	The construct '@\{-<n>\}' means the <n>th branch checked out
	before the current one.

	'<refname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
	The suffix '@\{upstream\}' to a ref (short form '<refname>@\{u\}') refers to
	the branch the ref is set to build on top of. A missing ref defaults
	to the current branch.

	'<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
	A suffix '{caret}' to a revision parameter means the first parent of
	that commit object. '{caret}<n>' means the <n>th parent (i.e.
	'<rev>{caret}'
	is equivalent to '<rev>{caret}1'). As a special rule,
	'<rev>{caret}0' means the commit itself and is used when '<rev>' is the
	object name of a tag object that refers to a commit object.

	'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
	A suffix '{tilde}<n>' to a revision parameter means the commit
	object that is the <n>th generation ancestor of the named
	commit object, following only the first parents. I.e. '<rev>{tilde}3' is
	equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
	'<rev>{caret}1{caret}1{caret}1'. See below for an illustration of
	the usage of this form.

	'<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
	A suffix '{caret}' followed by an object type name enclosed in
	brace pair means the object
	could be a tag, and dereference the tag recursively until an
	object of that type is found or the object cannot be
	dereferenced anymore (in which case, barf). '<rev>{caret}0'
	is a short-hand for '<rev>{caret}\{commit\}'.

	'<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
	A suffix '{caret}' followed by an empty brace pair
	means the object could be a tag,
	and dereference the tag recursively until a non-tag object is
	found.

	'<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
	A suffix '{caret}' to a revision parameter, followed by a brace
	pair that contains a text led by a slash,
	is the same as the ':/fix nasty bug' syntax below except that
	it returns the youngest matching commit which is reachable from
	the '<rev>' before '{caret}'.

	':/<text>', e.g. ':/fix nasty bug'::
	A colon, followed by a slash, followed by a text, names
	a commit whose commit message matches the specified regular expression.
	This name returns the youngest matching commit which is
	reachable from any ref. If the commit message starts with a
	'!' you have to repeat that; the special sequence ':/!',
	followed by something else than '!', is reserved for now.
	The regular expression can match any part of the commit message. To
	match messages starting with a string, one can use e.g. ':/^foo'.

	'<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
	A suffix ':' followed by a path names the blob or tree
	at the given path in the tree-ish object named by the part
	before the colon.
	':path' (with an empty part before the colon)
	is a special case of the syntax described next: content
	recorded in the index at the given path.
	A path starting with './' or '../' is relative to the current working directory.
	The given path will be converted to be relative to the working tree's root directory.
	This is most useful to address a blob or tree from a commit or tree that has
	the same tree structure as the working tree.

	':<n>:<path>', e.g. ':0:README', ':README'::
	A colon, optionally followed by a stage number (0 to 3) and a
	colon, followed by a path, names a blob object in the
	index at the given path. A missing stage number (and the colon
	that follows it) names a stage 0 entry. During a merge, stage
	1 is the common ancestor, stage 2 is the target branch's version
	(typically the current branch), and stage 3 is the version from
	the branch which is being merged.

	Here is an illustration, by Jon Loeliger. Both commit nodes B
	and C are parents of commit node A. Parent commits are ordered
	left-to-right.

	........................................
	G H I J
	\ / \ /
	D E F
	\ \| / \
	\ \| / \|
	\\|/ \|
	B C
	\ /
	\ /
	A
	........................................

	A = = A^0
	B = A^ = A^1 = A~1
	C = A^2 = A^2
	D = A^^ = A^1^1 = A~2
	E = B^2 = A^^2
	F = B^3 = A^^3
	G = A^^^ = A^1^1^1 = A~3
	H = D^2 = B^^2 = A^^^2 = A~2^2
	I = F^ = B^3^ = A^^3^
	J = F^2 = B^3^2 = A^^3^2


	SPECIFYING RANGES
	-----------------

	History traversing commands such as `git log` operate on a set
	of commits, not just a single commit. To these commands,
	specifying a single revision with the notation described in the
	previous section means the set of commits reachable from that
	commit, following the commit ancestry chain.

	To exclude commits reachable from a commit, a prefix '{caret}'
	notation is used. E.g. '{caret}r1 r2' means commits reachable
	from 'r2' but exclude the ones reachable from 'r1'.

	This set operation appears so often that there is a shorthand
	for it. When you have two commits 'r1' and 'r2' (named according
	to the syntax explained in SPECIFYING REVISIONS above), you can ask
	for commits that are reachable from r2 excluding those that are reachable
	from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.

	A similar notation 'r1\...r2' is called symmetric difference
	of 'r1' and 'r2' and is defined as
	'r1 r2 --not $(git merge-base --all r1 r2)'.
	It is the set of commits that are reachable from either one of
	'r1' or 'r2' but not from both.

	In these two shorthands, you can omit one end and let it default to HEAD.
	For example, 'origin..' is a shorthand for 'origin..HEAD' and asks "What
	did I do since I forked from the origin branch?" Similarly, '..origin'
	is a shorthand for 'HEAD..origin' and asks "What did the origin do since
	I forked from them?" Note that '..' would mean 'HEAD..HEAD' which is an
	empty range that is both reachable and unreachable from HEAD.

	Two other shorthands for naming a set that is formed by a commit
	and its parent commits exist. The 'r1{caret}@' notation means all
	parents of 'r1'. 'r1{caret}!' includes commit 'r1' but excludes
	all of its parents.

	To summarize:

	'<rev>'::
	Include commits that are reachable from (i.e. ancestors of)
	<rev>.

	'{caret}<rev>'::
	Exclude commits that are reachable from (i.e. ancestors of)
	<rev>.

	'<rev1>..<rev2>'::
	Include commits that are reachable from <rev2> but exclude
	those that are reachable from <rev1>.

	'<rev1>\...<rev2>'::
	Include commits that are reachable from either <rev1> or
	<rev2> but exclude those that are reachable from both.

	'<rev>{caret}@', e.g. 'HEAD{caret}@'::
	A suffix '{caret}' followed by an at sign is the same as listing
	all parents of '<rev>' (meaning, include anything reachable from
	its parents, but not the commit itself).

	'<rev>{caret}!', e.g. 'HEAD{caret}!'::
	A suffix '{caret}' followed by an exclamation mark is the same
	as giving commit '<rev>' and then all its parents prefixed with
	'{caret}' to exclude them (and their ancestors).

	Here are a handful of examples:

	D G H D
	D F G H I J D F
	^G D H D
	^D B E I J F B
	B..C C
	B...C G H D E B C
	^D B C E I J F B C
	C I J F C
	C^@ I J F
	C^! C
	F^! D G H D F