Documentation / git-describe.txton commit read-cache: fix index corruption with index v4 (0b90b88)
   1git-describe(1)
   2===============
   3
   4NAME
   5----
   6git-describe - Describe a commit using the most recent tag reachable from it
   7
   8
   9SYNOPSIS
  10--------
  11[verse]
  12'git describe' [--all] [--tags] [--contains] [--abbrev=<n>] [<commit-ish>...]
  13'git describe' [--all] [--tags] [--contains] [--abbrev=<n>] --dirty[=<mark>]
  14
  15DESCRIPTION
  16-----------
  17The command finds the most recent tag that is reachable from a
  18commit.  If the tag points to the commit, then only the tag is
  19shown.  Otherwise, it suffixes the tag name with the number of
  20additional commits on top of the tagged object and the
  21abbreviated object name of the most recent commit.
  22
  23By default (without --all or --tags) `git describe` only shows
  24annotated tags.  For more information about creating annotated tags
  25see the -a and -s options to linkgit:git-tag[1].
  26
  27OPTIONS
  28-------
  29<commit-ish>...::
  30        Commit-ish object names to describe.  Defaults to HEAD if omitted.
  31
  32--dirty[=<mark>]::
  33--broken[=<mark>]::
  34        Describe the state of the working tree.  When the working
  35        tree matches HEAD, the output is the same as "git describe
  36        HEAD".  If the working tree has local modification "-dirty"
  37        is appended to it.  If a repository is corrupt and Git
  38        cannot determine if there is local modification, Git will
  39        error out, unless `--broken' is given, which appends
  40        the suffix "-broken" instead.
  41
  42--all::
  43        Instead of using only the annotated tags, use any ref
  44        found in `refs/` namespace.  This option enables matching
  45        any known branch, remote-tracking branch, or lightweight tag.
  46
  47--tags::
  48        Instead of using only the annotated tags, use any tag
  49        found in `refs/tags` namespace.  This option enables matching
  50        a lightweight (non-annotated) tag.
  51
  52--contains::
  53        Instead of finding the tag that predates the commit, find
  54        the tag that comes after the commit, and thus contains it.
  55        Automatically implies --tags.
  56
  57--abbrev=<n>::
  58        Instead of using the default 7 hexadecimal digits as the
  59        abbreviated object name, use <n> digits, or as many digits
  60        as needed to form a unique object name.  An <n> of 0
  61        will suppress long format, only showing the closest tag.
  62
  63--candidates=<n>::
  64        Instead of considering only the 10 most recent tags as
  65        candidates to describe the input commit-ish consider
  66        up to <n> candidates.  Increasing <n> above 10 will take
  67        slightly longer but may produce a more accurate result.
  68        An <n> of 0 will cause only exact matches to be output.
  69
  70--exact-match::
  71        Only output exact matches (a tag directly references the
  72        supplied commit).  This is a synonym for --candidates=0.
  73
  74--debug::
  75        Verbosely display information about the searching strategy
  76        being employed to standard error.  The tag name will still
  77        be printed to standard out.
  78
  79--long::
  80        Always output the long format (the tag, the number of commits
  81        and the abbreviated commit name) even when it matches a tag.
  82        This is useful when you want to see parts of the commit object name
  83        in "describe" output, even when the commit in question happens to be
  84        a tagged version.  Instead of just emitting the tag name, it will
  85        describe such a commit as v1.2-0-gdeadbee (0th commit since tag v1.2
  86        that points at object deadbee....).
  87
  88--match <pattern>::
  89        Only consider tags matching the given `glob(7)` pattern,
  90        excluding the "refs/tags/" prefix.  This can be used to avoid
  91        leaking private tags from the repository. If given multiple times, a
  92        list of patterns will be accumulated, and tags matching any of the
  93        patterns will be considered. Use `--no-match` to clear and reset the
  94        list of patterns.
  95
  96--exclude <pattern>::
  97        Do not consider tags matching the given `glob(7)` pattern, excluding
  98        the "refs/tags/" prefix. This can be used to narrow the tag space and
  99        find only tags matching some meaningful criteria. If given multiple
 100        times, a list of patterns will be accumulated and tags matching any
 101        of the patterns will be excluded. When combined with --match a tag will
 102        be considered when it matches at least one --match pattern and does not
 103        match any of the --exclude patterns. Use `--no-exclude` to clear and
 104        reset the list of patterns.
 105
 106--always::
 107        Show uniquely abbreviated commit object as fallback.
 108
 109--first-parent::
 110        Follow only the first parent commit upon seeing a merge commit.
 111        This is useful when you wish to not match tags on branches merged
 112        in the history of the target commit.
 113
 114EXAMPLES
 115--------
 116
 117With something like git.git current tree, I get:
 118
 119        [torvalds@g5 git]$ git describe parent
 120        v1.0.4-14-g2414721
 121
 122i.e. the current head of my "parent" branch is based on v1.0.4,
 123but since it has a few commits on top of that,
 124describe has added the number of additional commits ("14") and
 125an abbreviated object name for the commit itself ("2414721")
 126at the end.
 127
 128The number of additional commits is the number
 129of commits which would be displayed by "git log v1.0.4..parent".
 130The hash suffix is "-g" + 7-char abbreviation for the tip commit
 131of parent (which was `2414721b194453f058079d897d13c4e377f92dc6`).
 132The "g" prefix stands for "git" and is used to allow describing the version of
 133a software depending on the SCM the software is managed with. This is useful
 134in an environment where people may use different SCMs.
 135
 136Doing a 'git describe' on a tag-name will just show the tag name:
 137
 138        [torvalds@g5 git]$ git describe v1.0.4
 139        v1.0.4
 140
 141With --all, the command can use branch heads as references, so
 142the output shows the reference path as well:
 143
 144        [torvalds@g5 git]$ git describe --all --abbrev=4 v1.0.5^2
 145        tags/v1.0.0-21-g975b
 146
 147        [torvalds@g5 git]$ git describe --all --abbrev=4 HEAD^
 148        heads/lt/describe-7-g975b
 149
 150With --abbrev set to 0, the command can be used to find the
 151closest tagname without any suffix:
 152
 153        [torvalds@g5 git]$ git describe --abbrev=0 v1.0.5^2
 154        tags/v1.0.0
 155
 156Note that the suffix you get if you type these commands today may be
 157longer than what Linus saw above when he ran these commands, as your
 158Git repository may have new commits whose object names begin with
 159975b that did not exist back then, and "-g975b" suffix alone may not
 160be sufficient to disambiguate these commits.
 161
 162
 163SEARCH STRATEGY
 164---------------
 165
 166For each commit-ish supplied, 'git describe' will first look for
 167a tag which tags exactly that commit.  Annotated tags will always
 168be preferred over lightweight tags, and tags with newer dates will
 169always be preferred over tags with older dates.  If an exact match
 170is found, its name will be output and searching will stop.
 171
 172If an exact match was not found, 'git describe' will walk back
 173through the commit history to locate an ancestor commit which
 174has been tagged.  The ancestor's tag will be output along with an
 175abbreviation of the input commit-ish's SHA-1. If `--first-parent` was
 176specified then the walk will only consider the first parent of each
 177commit.
 178
 179If multiple tags were found during the walk then the tag which
 180has the fewest commits different from the input commit-ish will be
 181selected and output.  Here fewest commits different is defined as
 182the number of commits which would be shown by `git log tag..input`
 183will be the smallest number of commits possible.
 184
 185GIT
 186---
 187Part of the linkgit:git[1] suite