GIT-CHECK-REF-FORMAT(1) Git Manual GIT-CHECK-REF-FORMAT(1)

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 the --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

+o Print the name of the previous thing checked out:

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

+o 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

Git 2.48.1 2025-01-13 GIT-CHECK-REF-FORMAT(1)