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git-check-ref-format - Ensures that a reference name is well formed
'git check-ref-format' [--normalize]
[--[no-]allow-onelevel] [--refspec-pattern]
'git check-ref-format' --branch <branchname-shorthand>
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:
. They can include slash `/` for hierarchical (directory)
grouping, but no slash-separated component can begin with a
dot `.` or end with the sequence `.lock`.
. 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.
. They cannot have two consecutive dots `..` anywhere.
. They cannot have ASCII control characters (i.e. bytes whose
values are lower than \040, or \177 `DEL`), space, tilde `~`,
caret `^`, or colon `:` anywhere.
. They cannot have question-mark `?`, asterisk `*`, or open
bracket `[` anywhere. See the `--refspec-pattern` option below for
an exception to this rule.
. They cannot begin or end with a slash `/` or contain multiple
consecutive slashes (see the `--normalize` option below for an
exception to this rule)
. They cannot end with a dot `.`.
. They cannot contain a sequence `@{`.
. They cannot be the single character `@`.
. 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 linkgit:gitrevisions[7]):
. 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`).
. A tilde `~` and caret `^` are used to introduce the postfix
'nth parent' and 'peel onion' operation.
. 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".
. 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.
Controls whether one-level refnames are accepted (i.e.,
refnames that do not contain multiple `/`-separated
components). The default is `--no-allow-onelevel`.
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 '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`.)
* 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 ; }
Part of the linkgit:git[1] suite