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9080a7f178
While we have multiple ways to show the value of a given reference, we
do not have any way to check whether a reference exists at all. While
commands like git-rev-parse(1) or git-show-ref(1) can be used to check
for reference existence in case the reference resolves to something
sane, neither of them can be used to check for existence in some other
scenarios where the reference does not resolve cleanly:
- References which have an invalid name cannot be resolved.
- References to nonexistent objects cannot be resolved.
- Dangling symrefs can be resolved via git-symbolic-ref(1), but this
requires the caller to special case existence checks depending on
whether or not a reference is symbolic or direct.
Furthermore, git-rev-list(1) and other commands do not let the caller
distinguish easily between an actually missing reference and a generic
error.
Taken together, this seems like sufficient motivation to introduce a
separate plumbing command to explicitly check for the existence of a
reference without trying to resolve its contents.
This new command comes in the form of `git show-ref --exists`. This
new mode will exit successfully when the reference exists, with a
specific exit code of 2 when it does not exist, or with 1 when there
has been a generic error.
Note that the only way to properly implement this command is by using
the internal `refs_read_raw_ref()` function. While the public function
`refs_resolve_ref_unsafe()` can be made to behave in the same way by
passing various flags, it does not provide any way to obtain the errno
with which the reference backend failed when reading the reference. As
such, it becomes impossible for us to distinguish generic errors from
the explicit case where the reference wasn't found.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
212 lines
6.5 KiB
Text
212 lines
6.5 KiB
Text
git-show-ref(1)
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===============
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NAME
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----
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git-show-ref - List references in a local repository
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SYNOPSIS
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--------
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[verse]
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'git show-ref' [--head] [-d | --dereference]
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[-s | --hash[=<n>]] [--abbrev[=<n>]] [--tags]
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[--heads] [--] [<pattern>...]
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'git show-ref' --verify [-q | --quiet] [-d | --dereference]
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[-s | --hash[=<n>]] [--abbrev[=<n>]]
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[--] [<ref>...]
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'git show-ref' --exclude-existing[=<pattern>]
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'git show-ref' --exists <ref>
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DESCRIPTION
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-----------
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Displays references available in a local repository along with the associated
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commit IDs. Results can be filtered using a pattern and tags can be
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dereferenced into object IDs. Additionally, it can be used to test whether a
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particular ref exists.
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By default, shows the tags, heads, and remote refs.
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The `--exclude-existing` form is a filter that does the inverse. It reads
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refs from stdin, one ref per line, and shows those that don't exist in
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the local repository.
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The `--exists` form can be used to check for the existence of a single
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references. This form does not verify whether the reference resolves to an
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actual object.
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Use of this utility is encouraged in favor of directly accessing files under
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the `.git` directory.
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OPTIONS
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-------
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--head::
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Show the HEAD reference, even if it would normally be filtered out.
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--heads::
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--tags::
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Limit to "refs/heads" and "refs/tags", respectively. These options
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are not mutually exclusive; when given both, references stored in
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"refs/heads" and "refs/tags" are displayed.
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-d::
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--dereference::
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Dereference tags into object IDs as well. They will be shown with `^{}`
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appended.
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-s::
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--hash[=<n>]::
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Only show the OID, not the reference name. When combined with
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`--dereference`, the dereferenced tag will still be shown after the OID.
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--verify::
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Enable stricter reference checking by requiring an exact ref path.
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Aside from returning an error code of 1, it will also print an error
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message if `--quiet` was not specified.
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--exists::
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Check whether the given reference exists. Returns an exit code of 0 if
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it does, 2 if it is missing, and 1 in case looking up the reference
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failed with an error other than the reference being missing.
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--abbrev[=<n>]::
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Abbreviate the object name. When using `--hash`, you do
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not have to say `--hash --abbrev`; `--hash=n` would do.
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-q::
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--quiet::
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Do not print any results to stdout. Can be used with `--verify` to
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silently check if a reference exists.
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--exclude-existing[=<pattern>]::
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Make `git show-ref` act as a filter that reads refs from stdin of the
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form `^(?:<anything>\s)?<refname>(?:\^{})?$`
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and performs the following actions on each:
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(1) strip `^{}` at the end of line if any;
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(2) ignore if pattern is provided and does not head-match refname;
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(3) warn if refname is not a well-formed refname and skip;
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(4) ignore if refname is a ref that exists in the local repository;
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(5) otherwise output the line.
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<pattern>...::
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Show references matching one or more patterns. Patterns are matched from
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the end of the full name, and only complete parts are matched, e.g.
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'master' matches 'refs/heads/master', 'refs/remotes/origin/master',
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'refs/tags/jedi/master' but not 'refs/heads/mymaster' or
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'refs/remotes/master/jedi'.
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OUTPUT
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------
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The output is in the format:
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------------
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<oid> SP <ref> LF
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------------
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For example,
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-----------------------------------------------------------------------------
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$ git show-ref --head --dereference
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832e76a9899f560a90ffd62ae2ce83bbeff58f54 HEAD
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832e76a9899f560a90ffd62ae2ce83bbeff58f54 refs/heads/master
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832e76a9899f560a90ffd62ae2ce83bbeff58f54 refs/heads/origin
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3521017556c5de4159da4615a39fa4d5d2c279b5 refs/tags/v0.99.9c
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6ddc0964034342519a87fe013781abf31c6db6ad refs/tags/v0.99.9c^{}
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055e4ae3ae6eb344cbabf2a5256a49ea66040131 refs/tags/v1.0rc4
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423325a2d24638ddcc82ce47be5e40be550f4507 refs/tags/v1.0rc4^{}
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...
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-----------------------------------------------------------------------------
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When using `--hash` (and not `--dereference`), the output is in the format:
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------------
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<oid> LF
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------------
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For example,
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-----------------------------------------------------------------------------
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$ git show-ref --heads --hash
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2e3ba0114a1f52b47df29743d6915d056be13278
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185008ae97960c8d551adcd9e23565194651b5d1
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03adf42c988195b50e1a1935ba5fcbc39b2b029b
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...
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-----------------------------------------------------------------------------
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EXAMPLES
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--------
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To show all references called "master", whether tags or heads or anything
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else, and regardless of how deep in the reference naming hierarchy they are,
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use:
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-----------------------------------------------------------------------------
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git show-ref master
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-----------------------------------------------------------------------------
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This will show "refs/heads/master" but also "refs/remote/other-repo/master",
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if such references exist.
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When using the `--verify` flag, the command requires an exact path:
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-----------------------------------------------------------------------------
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git show-ref --verify refs/heads/master
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-----------------------------------------------------------------------------
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will only match the exact branch called "master".
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If nothing matches, `git show-ref` will return an error code of 1,
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and in the case of verification, it will show an error message.
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For scripting, you can ask it to be quiet with the `--quiet` flag, which
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allows you to do things like
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-----------------------------------------------------------------------------
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git show-ref --quiet --verify -- "refs/heads/$headname" ||
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echo "$headname is not a valid branch"
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-----------------------------------------------------------------------------
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to check whether a particular branch exists or not (notice how we don't
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actually want to show any results, and we want to use the full refname for it
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in order to not trigger the problem with ambiguous partial matches).
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To show only tags, or only proper branch heads, use `--tags` and/or `--heads`
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respectively (using both means that it shows tags and heads, but not other
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random references under the refs/ subdirectory).
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To do automatic tag object dereferencing, use the `-d` or `--dereference`
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flag, so you can do
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-----------------------------------------------------------------------------
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git show-ref --tags --dereference
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-----------------------------------------------------------------------------
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to get a listing of all tags together with what they dereference.
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FILES
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-----
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`.git/refs/*`, `.git/packed-refs`
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SEE ALSO
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--------
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linkgit:git-for-each-ref[1],
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linkgit:git-ls-remote[1],
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linkgit:git-update-ref[1],
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linkgit:gitrepository-layout[5]
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GIT
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---
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Part of the linkgit:git[1] suite
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