git-check-ref-format - Ensures that a reference name is well formed
git check-ref-format [--normalize] [--[no-]allow-onelevel] [--refspec-pattern] <refname> 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:
h'-04' 1.h'+01'c
They can include slash / for hierarchical (directory) grouping, but no slash-separated component can begin with a dot . or end with the sequence .lock.
h'-04' 2.h'+01'c
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.
h'-04' 3.h'+01'c
They cannot have two consecutive dots .. anywhere.
h'-04' 4.h'+01'c
They cannot have ASCII control characters (i.e. bytes whose values are lower than e040, or e177 DEL), space, tilde ~, caret ^, or colon : anywhere.
h'-04' 5.h'+01'c
They cannot have question-mark ?, asterisk *, or open bracket [ anywhere. See the --refspec-pattern option below for an exception to this rule.
h'-04' 6.h'+01'c
They cannot begin or end with a slash / or contain multiple consecutive slashes (see the --normalize option below for an exception to this rule)
h'-04' 7.h'+01'c
They cannot end with a dot ..
h'-04' 8.h'+01'c
They cannot contain a sequence @{.
h'-04' 9.h'+01'c
They cannot be the single character @.
h'-04'10.h'+01'c
They cannot contain a e.
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)):
h'-04' 1.h'+01'c
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).
h'-04' 2.h'+01'c
A tilde ~ and caret ^ are used to introduce the postfix nth parent and peel onion operation.
h'-04' 3.h'+01'c
A colon : is used as in srcref:dstref to mean "use srcref(cqs 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".
h'-04' 4.h'+01'c
at-open-brace @{ is used as a notation to access a reflog entry.
With the --branch option, it expands the (lqprevious branch syntax(rq @{-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.
--[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 place of a one full pathname component (e.g., foo/*/bar but not foo/bar*).
--normalize
Normalize refname by removing any leading slash (/) characters and collapsing runs of adjacent slashes between name components into a single slash. Iff the normalized refname is valid then print it to standard output and exit with a status of 0. (--print is a deprecated way to spell --normalize.)
h'-04'(buh'+03'c
Print the name of the previous branch:
$ git check-ref-format --branch @{-1}
h'-04'(buh'+03'c
Determine the reference name to use for a new branch:
$ ref=$(git check-ref-format --normalize "refs/heads/$newbranch") || die "we do not like *(Aq$newbranch*(Aq as a branch name."
Part of the git(1) suite