git-describe - Online in the Cloud

PROGRAM:

NAME

git-describe - Describe a commit using the most recent tag reachable from it

SYNOPSIS

git describe [--all] [--tags] [--contains] [--abbrev=<n>] [<commit-ish>...]
git describe [--all] [--tags] [--contains] [--abbrev=<n>] --dirty[=<mark>]

DESCRIPTION

The command finds the most recent tag that is reachable from a commit. If the tag points
to the commit, then only the tag is shown. Otherwise, it suffixes the tag name with the
number of additional commits on top of the tagged object and the abbreviated object name
of the most recent commit.

By default (without --all or --tags) git describe only shows annotated tags. For more
information about creating annotated tags see the -a and -s options to git-tag(1).

OPTIONS

<commit-ish>...
Commit-ish object names to describe. Defaults to HEAD if omitted.

--dirty[=<mark>]
Describe the working tree. It means describe HEAD and appends <mark> (-dirty by
default) if the working tree is dirty.

--all
Instead of using only the annotated tags, use any ref found in refs/ namespace. This
option enables matching any known branch, remote-tracking branch, or lightweight tag.

--tags
Instead of using only the annotated tags, use any tag found in refs/tags namespace.
This option enables matching a lightweight (non-annotated) tag.

--contains
Instead of finding the tag that predates the commit, find the tag that comes after the
commit, and thus contains it. Automatically implies --tags.

--abbrev=<n>
Instead of using the default 7 hexadecimal digits as the abbreviated object name, use
<n> digits, or as many digits as needed to form a unique object name. An <n> of 0 will
suppress long format, only showing the closest tag.

--candidates=<n>
Instead of considering only the 10 most recent tags as candidates to describe the
input commit-ish consider up to <n> candidates. Increasing <n> above 10 will take
slightly longer but may produce a more accurate result. An <n> of 0 will cause only
exact matches to be output.

--exact-match
Only output exact matches (a tag directly references the supplied commit). This is a
synonym for --candidates=0.

--debug
Verbosely display information about the searching strategy being employed to standard
error. The tag name will still be printed to standard out.

--long
Always output the long format (the tag, the number of commits and the abbreviated
commit name) even when it matches a tag. This is useful when you want to see parts of
the commit object name in "describe" output, even when the commit in question happens
to be a tagged version. Instead of just emitting the tag name, it will describe such a
commit as v1.2-0-gdeadbee (0th commit since tag v1.2 that points at object
deadbee....).

--match <pattern>
Only consider tags matching the given glob(7) pattern, excluding the "refs/tags/"
prefix. This can be used to avoid leaking private tags from the repository.

--always
Show uniquely abbreviated commit object as fallback.

--first-parent
Follow only the first parent commit upon seeing a merge commit. This is useful when
you wish to not match tags on branches merged in the history of the target commit.

EXAMPLES

With something like git.git current tree, I get:

[torvalds@g5 git]$ git describe parent
v1.0.4-14-g2414721

i.e. the current head of my "parent" branch is based on v1.0.4, but since it has a few
commits on top of that, describe has added the number of additional commits ("14") and an
abbreviated object name for the commit itself ("2414721") at the end.

The number of additional commits is the number of commits which would be displayed by "git
log v1.0.4..parent". The hash suffix is "-g" + 7-char abbreviation for the tip commit of
parent (which was 2414721b194453f058079d897d13c4e377f92dc6). The "g" prefix stands for
"git" and is used to allow describing the version of a software depending on the SCM the
software is managed with. This is useful in an environment where people may use different
SCMs.

Doing a git describe on a tag-name will just show the tag name:

[torvalds@g5 git]$ git describe v1.0.4
v1.0.4

With --all, the command can use branch heads as references, so the output shows the
reference path as well:

[torvalds@g5 git]$ git describe --all --abbrev=4 v1.0.5^2
tags/v1.0.0-21-g975b

[torvalds@g5 git]$ git describe --all --abbrev=4 HEAD^
heads/lt/describe-7-g975b

With --abbrev set to 0, the command can be used to find the closest tagname without any
suffix:

[torvalds@g5 git]$ git describe --abbrev=0 v1.0.5^2
tags/v1.0.0

Note that the suffix you get if you type these commands today may be longer than what
Linus saw above when he ran these commands, as your Git repository may have new commits
whose object names begin with 975b that did not exist back then, and "-g975b" suffix alone
may not be sufficient to disambiguate these commits.

SEARCH STRATEGY

For each commit-ish supplied, git describe will first look for a tag which tags exactly
that commit. Annotated tags will always be preferred over lightweight tags, and tags with
newer dates will always be preferred over tags with older dates. If an exact match is
found, its name will be output and searching will stop.

If an exact match was not found, git describe will walk back through the commit history to
locate an ancestor commit which has been tagged. The ancestor’s tag will be output along
with an abbreviation of the input commit-ish’s SHA-1. If --first-parent was specified then
the walk will only consider the first parent of each commit.

If multiple tags were found during the walk then the tag which has the fewest commits
different from the input commit-ish will be selected and output. Here fewest commits
different is defined as the number of commits which would be shown by git log tag..input
will be the smallest number of commits possible.

GIT

Part of the git(1) suite

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