git-rev-parse(1)
================

NAME
----
git-rev-parse - Pick out and massage parameters


SYNOPSIS
--------
'git-rev-parse' [ --option ] <args>...

DESCRIPTION
-----------

Many git porcelainish commands take mixture of flags
(i.e. parameters that begin with a dash '-') and parameters
meant for underlying `git-rev-list` command they use internally
and flags and parameters for other commands they use as the
downstream of `git-rev-list`.  This command is used to
distinguish between them.


OPTIONS
-------
--revs-only::
        Do not output flags and parameters not meant for
        `git-rev-list` command.

--no-revs::
        Do not output flags and parameters meant for
        `git-rev-list` command.

--flags::
        Do not output non-flag parameters.

--no-flags::
        Do not output flag parameters.

--default <arg>::
        If there is no parameter given by the user, use `<arg>`
        instead.

--verify::
        The parameter given must be usable as a single, valid
        object name.  Otherwise barf and abort.

--sq::
        Usually the output is made one line per flag and
        parameter.  This option makes output a single line,
        properly quoted for consumption by shell.  Useful when
        you expect your parameter to contain whitespaces and
        newlines (e.g. when using pickaxe `-S` with
        `git-diff-\*`).

--not::
        When showing object names, prefix them with '{caret}' and
        strip '{caret}' prefix from the object names that already have
        one.

--symbolic::
        Usually the object names are output in SHA1 form (with
        possible '{caret}' prefix); this option makes them output in a
        form as close to the original input as possible.


--all::
        Show all refs found in `$GIT_DIR/refs`.

--branches::
        Show branch refs found in `$GIT_DIR/refs/heads`.

--tags::
        Show tag refs found in `$GIT_DIR/refs/tags`.

--remotes::
        Show tag refs found in `$GIT_DIR/refs/remotes`.

--show-prefix::
        When the command is invoked from a subdirectory, show the
        path of the current directory relative to the top-level
        directory.

--show-cdup::
        When the command is invoked from a subdirectory, show the
        path of the top-level directory relative to the current
        directory (typically a sequence of "../", or an empty string).

--git-dir::
        Show `$GIT_DIR` if defined else show the path to the .git directory.

--short, --short=number::
        Instead of outputting the full SHA1 values of object names try to
        abbreviate them to a shorter unique name. When no length is specified
        7 is used. The minimum length is 4.

--since=datestring, --after=datestring::
        Parses the date string, and outputs corresponding
        --max-age= parameter for git-rev-list command.

--until=datestring, --before=datestring::
        Parses the date string, and outputs corresponding
        --min-age= parameter for git-rev-list command.

<args>...::
        Flags and parameters to be parsed.


SPECIFYING REVISIONS
--------------------

A revision parameter typically, but not necessarily, names a
commit object.  They use what is called an 'extended SHA1'
syntax.

* The full SHA1 object name (40-byte hexadecimal string), or
  a substring of such that is unique within the repository.
  E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
  name the same commit object if there are no other object in
  your repository whose object name starts with dae86e.

* A symbolic ref name.  E.g. 'master' typically means the commit
  object referenced by $GIT_DIR/refs/heads/master.  If you
  happen to have both heads/master and tags/master, you can
  explicitly say 'heads/master' to tell git which one you mean.

* A suffix '@' followed by a date specification enclosed in a brace
  pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
  second ago\}' or '\{1979-02-26 18:30:00\}') to specify the value
  of the ref at a prior point in time.  This suffix may only be
  used immediately following a ref name and the ref must have an
  existing log ($GIT_DIR/logs/<ref>).

* A suffix '{caret}' to a revision parameter means the first parent of
  that commit object.  '{caret}<n>' means the <n>th parent (i.e.
  'rev{caret}'
  is equivalent to 'rev{caret}1').  As a special rule,
  'rev{caret}0' means the commit itself and is used when 'rev' is the
  object name of a tag object that refers to a commit object.

* A suffix '~<n>' to a revision parameter means the commit
  object that is the <n>th generation grand-parent of the named
  commit object, following only the first parent.  I.e. rev~3 is
  equivalent to rev{caret}{caret}{caret} which is equivalent to\
  rev{caret}1{caret}1{caret}1.

* A suffix '{caret}' followed by an object type name enclosed in
  brace pair (e.g. `v0.99.8{caret}\{commit\}`) means the object
  could be a tag, and dereference the tag recursively until an
  object of that type is found or the object cannot be
  dereferenced anymore (in which case, barf).  `rev{caret}0`
  introduced earlier is a short-hand for `rev{caret}\{commit\}`.

* A suffix '{caret}' followed by an empty brace pair
  (e.g. `v0.99.8{caret}\{\}`) means the object could be a tag,
  and dereference the tag recursively until a non-tag object is
  found.

Here is an illustration, by Jon Loeliger.  Both node B and C are
a commit parents of commit node A.  Parent commits are ordered
left-to-right.

    G   H   I   J
     \ /     \ /
      D   E   F
       \  |  / \
        \ | /   |
         \|/    |
          B     C
           \   /
            \ /
             A

    A =      = A^0
    B = A^   = A^1     = A~1
    C = A^2  = A^2
    D = A^^  = A^1^1   = A~2
    E = B^2  = A^^2
    F = B^3  = A^^3
    G = A^^^ = A^1^1^1 = A~3
    H = D^2  = B^^2    = A^^^2  = A~2^2
    I = F^   = B^3^    = A^^3^
    J = F^2  = B^3^2   = A^^3^2


SPECIFYING RANGES
-----------------

History traversing commands such as `git-log` operate on a set
of commits, not just a single commit.  To these commands,
specifying a single revision with the notation described in the
previous section means the set of commits reachable from that
commit, following the commit ancestry chain.

To exclude commits reachable from a commit, a prefix `{caret}`
notation is used.  E.g. "`{caret}r1 r2`" means commits reachable
from `r2` but exclude the ones reachable from `r1`.

This set operation appears so often that there is a shorthand
for it.  "`r1..r2`" is equivalent to "`{caret}r1 r2`".  It is
the difference of two sets (subtract the set of commits
reachable from `r1` from the set of commits reachable from
`r2`).

A similar notation "`r1\...r2`" is called symmetric difference
of `r1` and `r2` and is defined as
"`r1 r2 --not $(git-merge-base --all r1 r2)`".
It it the set of commits that are reachable from either one of
`r1` or `r2` but not from both.

Here are a few examples:

   D                A B D
   D F              A B C D F
   ^A G             B D
   ^A F             B C F
   G...I            C D F G I
   ^B G I           C D F G I

Author
------
Written by Linus Torvalds <torvalds@osdl.org> and
Junio C Hamano <junkio@cox.net>

Documentation
--------------
Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.

GIT
---
Part of the gitlink:git[7] suite