Add new @ shortcut for HEAD
[git/git.git] / Documentation / git-check-ref-format.txt
1 git-check-ref-format(1)
2 =======================
3
4 NAME
5 ----
6 git-check-ref-format - Ensures that a reference name is well formed
7
8 SYNOPSIS
9 --------
10 [verse]
11 'git check-ref-format' [--normalize]
12 [--[no-]allow-onelevel] [--refspec-pattern]
13 <refname>
14 'git check-ref-format' --branch <branchname-shorthand>
15
16 DESCRIPTION
17 -----------
18 Checks if a given 'refname' is acceptable, and exits with a non-zero
19 status if it is not.
20
21 A reference is used in Git to specify branches and tags. A
22 branch head is stored in the `refs/heads` hierarchy, while
23 a tag is stored in the `refs/tags` hierarchy of the ref namespace
24 (typically in `$GIT_DIR/refs/heads` and `$GIT_DIR/refs/tags`
25 directories or, as entries in file `$GIT_DIR/packed-refs`
26 if refs are packed by `git gc`).
27
28 Git imposes the following rules on how references are named:
29
30 . They can include slash `/` for hierarchical (directory)
31 grouping, but no slash-separated component can begin with a
32 dot `.` or end with the sequence `.lock`.
33
34 . They must contain at least one `/`. This enforces the presence of a
35 category like `heads/`, `tags/` etc. but the actual names are not
36 restricted. If the `--allow-onelevel` option is used, this rule
37 is waived.
38
39 . They cannot have two consecutive dots `..` anywhere.
40
41 . They cannot have ASCII control characters (i.e. bytes whose
42 values are lower than \040, or \177 `DEL`), space, tilde `~`,
43 caret `^`, or colon `:` anywhere.
44
45 . They cannot have question-mark `?`, asterisk `*`, or open
46 bracket `[` anywhere. See the `--refspec-pattern` option below for
47 an exception to this rule.
48
49 . They cannot begin or end with a slash `/` or contain multiple
50 consecutive slashes (see the `--normalize` option below for an
51 exception to this rule)
52
53 . They cannot end with a dot `.`.
54
55 . They cannot contain a sequence `@{`.
56
57 . They cannot be the single character `@`.
58
59 . They cannot contain a `\`.
60
61 These rules make it easy for shell script based tools to parse
62 reference names, pathname expansion by the shell when a reference name is used
63 unquoted (by mistake), and also avoids ambiguities in certain
64 reference name expressions (see linkgit:gitrevisions[7]):
65
66 . A double-dot `..` is often used as in `ref1..ref2`, and in some
67 contexts this notation means `^ref1 ref2` (i.e. not in
68 `ref1` and in `ref2`).
69
70 . A tilde `~` and caret `^` are used to introduce the postfix
71 'nth parent' and 'peel onion' operation.
72
73 . A colon `:` is used as in `srcref:dstref` to mean "use srcref\'s
74 value and store it in dstref" in fetch and push operations.
75 It may also be used to select a specific object such as with
76 'git cat-file': "git cat-file blob v1.3.3:refs.c".
77
78 . at-open-brace `@{` is used as a notation to access a reflog entry.
79
80 With the `--branch` option, it expands the ``previous branch syntax''
81 `@{-n}`. For example, `@{-1}` is a way to refer the last branch you
82 were on. This option should be used by porcelains to accept this
83 syntax anywhere a branch name is expected, so they can act as if you
84 typed the branch name.
85
86 OPTIONS
87 -------
88 --[no-]allow-onelevel::
89 Controls whether one-level refnames are accepted (i.e.,
90 refnames that do not contain multiple `/`-separated
91 components). The default is `--no-allow-onelevel`.
92
93 --refspec-pattern::
94 Interpret <refname> as a reference name pattern for a refspec
95 (as used with remote repositories). If this option is
96 enabled, <refname> is allowed to contain a single `*`
97 in place of a one full pathname component (e.g.,
98 `foo/*/bar` but not `foo/bar*`).
99
100 --normalize::
101 Normalize 'refname' by removing any leading slash (`/`)
102 characters and collapsing runs of adjacent slashes between
103 name components into a single slash. Iff the normalized
104 refname is valid then print it to standard output and exit
105 with a status of 0. (`--print` is a deprecated way to spell
106 `--normalize`.)
107
108
109 EXAMPLES
110 --------
111
112 * Print the name of the previous branch:
113 +
114 ------------
115 $ git check-ref-format --branch @{-1}
116 ------------
117
118 * Determine the reference name to use for a new branch:
119 +
120 ------------
121 $ ref=$(git check-ref-format --normalize "refs/heads/$newbranch") ||
122 die "we do not like '$newbranch' as a branch name."
123 ------------
124
125 GIT
126 ---
127 Part of the linkgit:git[1] suite