NAME
----
-git-check-ref-format - Make sure ref name is well formed
+git-check-ref-format - Ensures that a reference name is well formed
SYNOPSIS
--------
+[verse]
'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 non-zero if
-it is not.
+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 `$GIT_DIR/refs/heads` directory, and
-a tag is stored under `$GIT_DIR/refs/tags` directory. git
-imposes the following rules on how refs are named:
+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`).
-. It can include slash `/` for hierarchical (directory)
+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 `.`;
+ dot `.`.
+
+. They must contain at least one `/`. This enforces the presence of a
+ category like `heads/`, `tags/` etc. but the actual names are not
+ restricted.
-. It cannot have two consecutive dots `..` anywhere;
+. They cannot have two consecutive dots `..` anywhere.
-. It cannot have ASCII control character (i.e. bytes whose
+. They cannot have ASCII control characters (i.e. bytes whose
values are lower than \040, or \177 `DEL`), space, tilde `~`,
caret `{caret}`, colon `:`, question-mark `?`, asterisk `*`,
- or open bracket `[` anywhere;
+ or open bracket `[` anywhere.
+
+. They cannot end with a slash `/` nor a dot `.`.
-. It cannot end with a slash `/`.
+. They cannot end with the sequence `.lock`.
-These rules makes it easy for shell script based tools to parse
-refnames, pathname expansion by the shell when a refname is used
+. They cannot contain a sequence `@{`.
+
+. 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
-refname expressions (see linkgit:git-rev-parse[1]). Namely:
+reference name expressions (see linkgit:gitrevisions[7]):
-. double-dot `..` are often used as in `ref1..ref2`, and in some
- context this notation means `{caret}ref1 ref2` (i.e. not in
- ref1 and in ref2).
+. A double-dot `..` is often used as in `ref1..ref2`, and in some
+ contexts this notation means `{caret}ref1 ref2` (i.e. not in
+ `ref1` and in `ref2`).
-. tilde `~` and caret `{caret}` are used to introduce postfix
+. A tilde `~` and caret `{caret}` are used to introduce the postfix
'nth parent' and 'peel onion' operation.
-. colon `:` is used as in `srcref:dstref` to mean "use srcref\'s
+. 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".
+ '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 `--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
---