GITREVISIONS

Section: Git Manual (7)
Updated: 11/29/2016
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NAME

gitrevisions - specifying revisions and ranges for Git  

SYNOPSIS

gitrevisions  

DESCRIPTION

Many Git commands take revision parameters as arguments. Depending on the command, they denote a specific commit or, for commands which walk the revision graph (such as git-log(1)), all commits which are reachable from that commit. For commands that walk the revision graph one can also specify a range of revisions explicitly.

In addition, some Git commands (such as git-show(1)) also take revision parameters which denote other objects than commits, e.g. blobs ("files") or trees ("directories of files").  

SPECIFYING REVISIONS

A revision parameter <rev> typically, but not necessarily, names a commit object. It uses what is called an extended SHA-1 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 SHA-1 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:

1. 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);

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

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

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

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

6. 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 preferred as some output processing may assume ref names in UTF-8.

@

@ alone is a shortcut for HEAD.

<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/commit checked out before the current one.

<branchname>@{upstream}, e.g. master@{upstream}, @{u}

The suffix @{upstream} to a branchname (short form <branchname>@{u}) refers to the branch that the branch specified by branchname is set to build on top of (configured with branch.<name>.remote and branch.<name>.merge). A missing branchname defaults to the current one.

<branchname>@{push}, e.g. master@{push}, @{push}

The suffix @{push} reports the branch "where we would push to" if git push were run while branchname was checked out (or the current HEAD if no branchname is specified). Since our push destination is in a remote repository, of course, we report the local tracking branch that corresponds to that branch (i.e., something in refs/remotes/).

Herecqs an example to make it more clear:

$ git config push.default current
$ git config remote.pushdefault myfork
$ git checkout -b mybranch origin/master

$ git rev-parse --symbolic-full-name @{upstream}
refs/remotes/origin/master

$ git rev-parse --symbolic-full-name @{push}
refs/remotes/myfork/mybranch

Note in the example that we set up a triangular workflow, where we pull from one location and push to another. In a non-triangular workflow, @{push} is the same as @{upstream}, and there is no need for it.

<rev>^, e.g. HEAD^, v1.5.1^0

A suffix ^ to a revision parameter means the first parent of that commit object. ^<n> means the <n>th parent (i.e. <rev>^ is equivalent to <rev>^1). As a special rule, <rev>^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>~<n>, e.g. master~3

A suffix ~<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>~3 is equivalent to <rev>^^^ which is equivalent to <rev>^1^1^1. See below for an illustration of the usage of this form.

<rev>^{<type>}, e.g. v0.99.8^{commit}

A suffix ^ followed by an object type name enclosed in brace pair means dereference the object at <rev> recursively until an object of type <type> is found or the object cannot be dereferenced anymore (in which case, barf). For example, if <rev> is a commit-ish, <rev>^{commit} describes the corresponding commit object. Similarly, if <rev> is a tree-ish, <rev>^{tree} describes the corresponding tree object. <rev>^0 is a short-hand for <rev>^{commit}.

rev^{object} can be used to make sure rev names an object that exists, without requiring rev to be a tag, and without dereferencing rev; because a tag is already an object, it does not have to be dereferenced even once to get to an object.

rev^{tag} can be used to ensure that rev identifies an existing tag object.

<rev>^{}, e.g. v0.99.8^{}

A suffix ^ 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>^{/<text>}, e.g. HEAD^{/fix nasty bug}

A suffix ^ 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 ^.

:/<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. The regular expression can match any part of the commit message. To match messages starting with a string, one can use e.g. :/^foo. The special sequence :/! is reserved for modifiers to what is matched. :/!-foo performs a negative match, while :/!!foo matches a literal ! character, followed by foo. Any other sequence beginning with :/! is reserved for now.

<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 treecqs 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 branchcqs 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.

For these commands, specifying a single revision, using the notation described in the previous section, means the set of commits reachable from the given commit.

A commitcqs reachable set is the commit itself and the commits in its ancestry chain.  

Commit Exclusions

^<rev> (caret) Notation

To exclude commits reachable from a commit, a prefix ^ notation is used. E.g. ^r1 r2 means commits reachable from r2 but exclude the ones reachable from r1 (i.e. r1 and its ancestors).

 

Dotted Range Notations

The .. (two-dot) Range Notation

The ^r1 r2 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 ^r1 r2 and it can be written as r1..r2.

The ... (three dot) Symmetric Difference Notation

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 (left side) or r2 (right side) but not from both.

In these two shorthand notations, 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.  

Other <rev>^ Parent Shorthand Notations

Three other shorthands exist, particularly useful for merge commits, for naming a set that is formed by a commit and its parent commits.

The r1^@ notation means all parents of r1.

The r1^! notation includes commit r1 but excludes all of its parents. By itself, this notation denotes the single commit r1.

The <rev>^-{<n>} notation includes <rev> but excludes the <n>th parent (i.e. a shorthand for <rev>^<n>..<rev>), with <n> = 1 if not given. This is typically useful for merge commits where you can just pass <commit>^- to get all the commits in the branch that was merged in merge commit <commit> (including <commit> itself).

While <rev>^<n> was about specifying a single commit parent, these three notations also consider its parents. For example you can say HEAD^2^@, however you cannot say HEAD^@^2.  

REVISION RANGE SUMMARY

<rev>

Include commits that are reachable from <rev> (i.e. <rev> and its ancestors).

^<rev>

Exclude commits that are reachable from <rev> (i.e. <rev> and its ancestors).

<rev1>..<rev2>

Include commits that are reachable from <rev2> but exclude those that are reachable from <rev1>. When either <rev1> or <rev2> is omitted, it defaults to HEAD.

<rev1>...<rev2>

Include commits that are reachable from either <rev1> or <rev2> but exclude those that are reachable from both. When either <rev1> or <rev2> is omitted, it defaults to HEAD.

<rev>^@, e.g. HEAD^@

A suffix ^ 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>^!, e.g. HEAD^!

A suffix ^ followed by an exclamation mark is the same as giving commit <rev> and then all its parents prefixed with ^ to exclude them (and their ancestors).

<rev>^-{<n>}, e.g. HEAD^-, HEAD^-2

Equivalent to <rev>^<n>..<rev>, with <n> = 1 if not given.

Here are a handful of examples using the Loeliger illustration above, with each step in the notationcqs expansion and selection carefully spelt out:

Args   Expanded arguments    Selected commits
D                            G H D
D F                          G H I J D F
^G D                         H D
^D B                         E I J F B
^D B C                       E I J F B C
C                            I J F C
B..C   = ^B C                C
B...C  = B ^F C              G H D E B C
B^-    = B^..B
       = ^B^1 B              E I J F B
C^@    = C^1
       = F                   I J F
B^@    = B^1 B^2 B^3
       = D E F               D G H E F I J
C^!    = C ^C^@
       = C ^C^1
       = C ^F                C
B^!    = B ^B^@
       = B ^B^1 ^B^2 ^B^3
       = B ^D ^E ^F          B
F^! D  = F ^I ^J D           G H D F

 

SEE ALSO

git-rev-parse(1)  

GIT

Part of the git(1) suite

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Index

NAME

SYNOPSIS

DESCRIPTION

SPECIFYING REVISIONS

SPECIFYING RANGES

Commit Exclusions

Dotted Range Notations

Other <rev>^ Parent Shorthand Notations

REVISION RANGE SUMMARY

SEE ALSO

GIT