git describe [--all] [--tags] [--contains] [--abbrev=<n>] <committish>...
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).
<committish>...
--all
--tags
--contains
--abbrev=<n>
--candidates=<n>
--exact-match
--debug
--long
--match <pattern>
--always
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).
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 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
For each committish 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 ancestorcqs tag will be output along with an abbreviation of the input committishcqs SHA1.
If multiple tags were found during the walk then the tag which has the fewest commits different from the input committish 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.
Written by Linus Torvalds <m[blue]torvalds@osdl.orgm[][1]>, but somewhat butchered by Junio C Hamano <m[blue]gitster@pobox.comm[][2]>. Later significantly updated by Shawn Pearce <m[blue]spearce@spearce.orgm[][3]>.
Documentation by David Greaves, Junio C Hamano and the git-list <m[blue]git@vger.kernel.orgm[][4]>.
Part of the git(1) suite