Reputation: 49141

What does the caret (^) character mean in Git?

I saw an answer to a question here that helps restore a deleted file in git.

The solution was

git checkout <deleting_commit>^ -- <deleted_file_path>

What does the caret character (^) do? I’ve seen it elsewhere doing very useful things in git. It’s magical. Someone please spoil it for me and tell me what it does?

Upvotes: 170

Answers (9)

Greg Bacon

Reputation: 139441

HEAD^ means the first parent of the tip of the current branch.

Remember that git commits can have more than one immediate parent. HEAD^ is short for HEAD^1, and you can also address HEAD^2 and so on as appropriate. Any commit with multiple parents is the product of a merge or a merge commit.

You can get to parents of any commit, not just HEAD. You can also move back through generations to any reachable ancestor: for example, master~2 means the grandparent of the tip of the master branch, favoring the first parent in cases of ambiguity. These specifiers can be chained arbitrarily. For example:

HEAD^^^, HEAD~~~, or HEAD~3 all refer to the great-grandparent commit, three generations back.
- HEAD^3 is different: it means the third immediate parent of a merge commit — and strains the analogy to biology.
topic~3^2 starts at the tag or tip of the branch named topic, goes three generations back, and selects that merge commit’s (the great-grandparent’s) second immediate parent — the great-great-grandfather if you think of git history as being primarily matrilineal.

The ^ (Caret) and ~ (Tilde) selectors

The difference between HEAD^ (Caret) and HEAD~ (Tilde) is how they traverse history backwards from a specified starting point, in this particular case HEAD.

Tilde ~

<rev>~[<n>] = select <n>th generation ancestor, following only first* parents

Caret ^

<rev>^[<n>] = select <n>th parent of first generation ancestors

*First parent is always the left hand side of the merge, e.g. the commit on the branch that got merged into.

Joining ~ and ^ together

As seen in the illustration below the two selectors ~ and ^ can be used in combination. Also note that instead of using HEAD as a starting point, any regular reference can be used such as a branch, tag or even a commit hash.

Further more, depending on what ancestor is intended to be selected ^ and ~ can be used interchangeably as seen below in the table.

Source: A thorough rundown can be found in this blog post on the subject.

Upvotes: 7

cdosborn

Reputation: 3449

Here's a visual explanation. Suppose you have a history like so:

                      master  
  ... <- B <- C <- D
             /
... <- E <- F
              feature

When feature was merged into master, C was created with two ancestors. Git assigns these ancestors numbers. The mainline ancestor B is assigned 1 and the feature ancestor F is assigned 2.

Thus C^1 refers to B and C^2 refers to F. C^ is an alias for C^1.

You would only ever use <rev>^3. if you had performed a merge of three branches.

Upvotes: 15

Ncat

Reputation: 415

Greg Bacon gave a great link, but it's pretty dense. The Git introductory docs online also introduce revision and range specifiers:

https://git-scm.com/book/en/v2/Git-Tools-Revision-Selection

Upvotes: 2

cmcginty

Reputation: 116958

The ^ (caret) can also be used when specifying ranges.

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.

<rev>

Include commits that are reachable from (i.e. ancestors of) .

^<rev>

Exclude commits that are reachable from (i.e. ancestors of) .

Upvotes: 30

TALLBOY

Reputation: 1077

The (^) gets the parent source of the command i.e. HEAD^ will get the parent of HEAD.

Upvotes: 4

Amber

Reputation: 526573

The carat represents a commit offset (parent). So for instance, HEAD^ means "one commit from HEAD" and HEAD^^^ means "three commits from HEAD".

Upvotes: 4

mipadi

Reputation: 410592

It means "parent of". So HEAD^ means "the parent of the current HEAD". You can even chain them together: HEAD^^ means "the parent of the parent of the current HEAD" (i.e., the grandparent of the current HEAD), HEAD^^^ means "the parent of the parent of the parent of the current HEAD", and so forth.

Upvotes: 27

mopoke

Reputation: 10685

The caret refers to the parent of a particular commit. E.g. HEAD^ refers to the parent of the current HEAD commmit. (also, HEAD^^ refers to the grandparent).

Upvotes: 9