git-check-ref-format(1)

# 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 [--normalize]
           [--[no-]allow-onelevel] [--refspec-pattern]
           <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 in the `refs/heads` hierarchy, while a tag is stored in the `refs/tags` hierarchy of the ref namespace (typically in `$GIT_DIR/refs/heads` and `$GIT_DIR/refs/tags` directories or, as entries in file `$GIT_DIR/packed-refs` if refs are packed by `git gc`).

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 `.` or end with the sequence `.lock`.

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. If the `--allow-onelevel` option is used, this rule is waived.

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 `^`, or colon `:` anywhere.

5. They cannot have question-mark `?`, asterisk `*`, or open bracket `[` anywhere. See the `--refspec-pattern` option below for an exception to this rule.

6. They cannot begin or end with a slash `/` or contain multiple consecutive slashes (see the `--normalize` option below for an exception to this rule)

7. They cannot end with a dot `.`.

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

9. They cannot be the single character `@`.

10. 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 avoid 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 `--branch` option, the command takes a name and checks if it can be used as a valid branch name (e.g. when creating a new branch). But be cautious when using the previous checkout syntax that may refer to a detached HEAD state. The rule `git check-ref-format --branch $name` implements may be stricter than what `git check-ref-format refs/heads/$name` says (e.g. a dash may appear at the beginning of a ref component, but it is explicitly forbidden at the beginning of a branch name). When run with `--branch` option in a repository, the input is first expanded for the “previous checkout syntax” `@{-n}`. For example, `@{-1}` is a way to refer the last thing that was checked out using "git switch" or "git checkout" operation. 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. As an exception note that, the “previous checkout operation” might result in a commit object name when the N-th last thing checked out was not a branch.

## OPTIONS

--[no-]allow-onelevel

  Controls whether one-level refnames are accepted (i.e., refnames that do not contain multiple `/`-separated components). The default is `--no-allow-onelevel`.

--refspec-pattern

  Interpret <refname> as a reference name pattern for a refspec (as used with remote repositories). If this option is enabled, <refname> is allowed to contain a single `*` in the refspec (e.g., `foo/bar*/baz` or `foo/bar*baz/` but not `foo/bar*/baz*`).

--normalize

  Normalize refname by removing any leading slash (`/`) characters and collapsing runs of adjacent slashes between name components into a single slash. If the normalized refname is valid then print it to standard output and exit with a status of 0, otherwise exit with a non-zero status. (`--print` is a deprecated way to spell `--normalize`.)

## EXAMPLES

- Print the name of the previous thing checked out:

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

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

      $ ref=$(git check-ref-format --normalize "refs/heads/$newbranch")||
      { echo "we do not like '$newbranch' as a branch name." >&2 ; exit 1 ; }

## GIT

Part of the git(1) suite