# git-check-ref-format(1) Manual Page

## NAME

git-check-ref-format - Ensures that a reference name is well formed

## SYNOPSIS

git check-ref-format <refname> git check-ref-format --print <refname> git check-ref-format --branch <branchname-shorthand>

## DESCRIPTION

Checks if a given refname is acceptable, and exits with a non-zero status if it is not.

A reference is used in git to specify branches and tags. A branch head is stored under the `$GIT_DIR/refs/heads` directory, and a tag is stored under the `$GIT_DIR/refs/tags` directory (or, if refs are packed by `git gc`, as entries in the `$GIT_DIR/packed-refs` file). git imposes the following rules on how references are named:

1. They can include slash `/` for hierarchical (directory) grouping, but no slash-separated component can begin with a dot `.`.

2. They must contain at least one `/`. This enforces the presence of a category like `heads/`, `tags/` etc. but the actual names are not restricted.

3. They cannot have two consecutive dots `..` anywhere.

4. They cannot have ASCII control characters (i.e. bytes whose values are lower than \040, or \177 `DEL`), space, tilde `~`, caret `^`, colon `:`, question-mark `?`, asterisk `*`, or open bracket `[` anywhere.

5. They cannot end with a slash `/` nor a dot `.`.

6. They cannot end with the sequence `.lock`.

7. They cannot contain a sequence `@{`.

8. They cannot contain a `\`.

These rules make it easy for shell script based tools to parse reference names, pathname expansion by the shell when a reference name is used unquoted (by mistake), and also avoids ambiguities in certain reference name expressions (see gitrevisions(7)):

1. A double-dot `..` is often used as in `ref1..ref2`, and in some contexts this notation means `^ref1 ref2` (i.e. not in `ref1` and in `ref2`).

2. A tilde `~` and caret `^` are used to introduce the postfix nth parent and peel onion operation.

3. A colon `:` is used as in `srcref:dstref` to mean "use srcref’s value and store it in dstref" in fetch and push operations. It may also be used to select a specific object such as with git cat-file: "git cat-file blob v1.3.3:refs.c".

4. at-open-brace `@{` is used as a notation to access a reflog entry.

With the `--print` option, if refname is acceptable, it prints the canonicalized name of a hypothetical reference with that name. That is, it prints refname with any extra `/` characters removed.

With the `--branch` option, it expands the “previous branch syntax” `@{-n}`. For example, `@{-1}` is a way to refer the last branch you were on. This option should be used by porcelains to accept this syntax anywhere a branch name is expected, so they can act as if you typed the branch name.

## EXAMPLES

- Print the name of the previous branch:

      $ git check-ref-format --branch @{-1}

- Determine the reference name to use for a new branch:

      $ ref=$(git check-ref-format --print "refs/heads/$newbranch") ||
      die "we do not like '$newbranch' as a branch name."

## GIT

Part of the git(1) suite