GIT-REV-PARSE(1)                   Git Manual                   GIT-REV-PARSE(1)

       git-rev-parse - Pick out and massage parameters

       git rev-parse [<options>] <args>...

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

   Operation Modes
       Each of these options must appear first on the command line.

           Use git rev-parse in option parsing mode (see PARSEOPT section

           Use git rev-parse in shell quoting mode (see SQ-QUOTE section below).
           In contrast to the --sq option below, this mode does only quoting.
           Nothing else is done to command input.

   Options for --parseopt
           Only meaningful in --parseopt mode. Tells the option parser to echo
           out the first -- met instead of skipping it.

           Only meaningful in --parseopt mode. Lets the option parser stop at
           the first non-option argument. This can be used to parse sub-commands
           that take options themselves.

           Only meaningful in --parseopt mode. Output the options in their long
           form if available, and with their arguments stuck.

   Options for Filtering
           Do not output flags and parameters not meant for git rev-list

           Do not output flags and parameters meant for git rev-list command.

           Do not output non-flag parameters.

           Do not output flag parameters.

   Options for Output
       --default <arg>
           If there is no parameter given by the user, use <arg> instead.

       --prefix <arg>
           Behave as if git rev-parse was invoked from the <arg> subdirectory of
           the working tree. Any relative filenames are resolved as if they are
           prefixed by <arg> and will be printed in that form.

           This can be used to convert arguments to a command run in a
           subdirectory so that they can still be used after moving to the
           top-level of the repository. For example:

               prefix=$(git rev-parse --show-prefix)
               cd "$(git rev-parse --show-toplevel)"
               # rev-parse provides the -- needed for 'set'
               eval "set $(git rev-parse --sq --prefix "$prefix" -- "$@")"

           Verify that exactly one parameter is provided, and that it can be
           turned into a raw 20-byte SHA-1 that can be used to access the object
           database. If so, emit it to the standard output; otherwise, error

           If you want to make sure that the output actually names an object in
           your object database and/or can be used as a specific type of object
           you require, you can add the ^{type} peeling operator to the
           parameter. For example, git rev-parse "$VAR^{commit}" will make sure
           $VAR names an existing object that is a commit-ish (i.e. a commit, or
           an annotated tag that points at a commit). To make sure that $VAR
           names an existing object of any type, git rev-parse "$VAR^{object}"
           can be used.

           Note that if you are verifying a name from an untrusted source, it is
           wise to use --end-of-options so that the name argument is not
           mistaken for another option.

       -q, --quiet
           Only meaningful in --verify mode. Do not output an error message if
           the first argument is not a valid object name; instead exit with
           non-zero status silently. SHA-1s for valid object names are printed
           to stdout on success.

           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-*). In
           contrast to the --sq-quote option, the command input is still
           interpreted as usual.

           Same as --verify but shortens the object name to a unique prefix with
           at least length characters. The minimum length is 4, the default is
           the effective value of the core.abbrev configuration variable (see

           When showing object names, prefix them with ^ and strip ^ prefix from
           the object names that already have one.

           A non-ambiguous short name of the objects name. The option
           core.warnAmbiguousRefs is used to select the strict abbreviation

           Usually the object names are output in SHA-1 form (with possible ^
           prefix); this option makes them output in a form as close to the
           original input as possible.

           This is similar to --symbolic, but it omits input that are not refs
           (i.e. branch or tag names; or more explicitly disambiguating
           "heads/master" form, when you want to name the "master" branch when
           there is an unfortunately named tag "master"), and show them as full
           refnames (e.g. "refs/heads/master").

   Options for Objects
           Show all refs found in refs/.

       --branches[=pattern], --tags[=pattern], --remotes[=pattern]
           Show all branches, tags, or remote-tracking branches, respectively
           (i.e., refs found in refs/heads, refs/tags, or refs/remotes,

           If a pattern is given, only refs matching the given shell glob are
           shown. If the pattern does not contain a globbing character (?, *, or
           [), it is turned into a prefix match by appending /*.

           Show all refs matching the shell glob pattern pattern. If the pattern
           does not start with refs/, this is automatically prepended. If the
           pattern does not contain a globbing character (?, *, or [), it is
           turned into a prefix match by appending /*.

           Do not include refs matching <glob-pattern> that the next --all,
           --branches, --tags, --remotes, or --glob would otherwise consider.
           Repetitions of this option accumulate exclusion patterns up to the
           next --all, --branches, --tags, --remotes, or --glob option (other
           options or arguments do not clear accumulated patterns).

           The patterns given should not begin with refs/heads, refs/tags, or
           refs/remotes when applied to --branches, --tags, or --remotes,
           respectively, and they must begin with refs/ when applied to --glob
           or --all. If a trailing /* is intended, it must be given explicitly.

           Show every object whose name begins with the given prefix. The
           <prefix> must be at least 4 hexadecimal digits long to avoid listing
           each and every object in the repository by mistake.

   Options for Files
           List the GIT_* environment variables that are local to the repository
           (e.g. GIT_DIR or GIT_WORK_TREE, but not GIT_EDITOR). Only the names
           of the variables are listed, not their value, even if they are set.

           Show $GIT_DIR if defined. Otherwise show the path to the .git
           directory. The path shown, when relative, is relative to the current
           working directory.

           If $GIT_DIR is not defined and the current directory is not detected
           to lie in a Git repository or work tree print a message to stderr and
           exit with nonzero status.

           Like --git-dir, but its output is always the canonicalized absolute

           Show $GIT_COMMON_DIR if defined, else $GIT_DIR.

           When the current working directory is below the repository directory
           print "true", otherwise "false".

           When the current working directory is inside the work tree of the
           repository print "true", otherwise "false".

           When the repository is bare print "true", otherwise "false".

           When the repository is shallow print "true", otherwise "false".

       --resolve-git-dir <path>
           Check if <path> is a valid repository or a gitfile that points at a
           valid repository, and print the location of the repository. If <path>
           is a gitfile then the resolved path to the real repository is

       --git-path <path>
           Resolve "$GIT_DIR/<path>" and takes other path relocation variables
           such as $GIT_OBJECT_DIRECTORY, $GIT_INDEX_FILE... into account. For
           example, if $GIT_OBJECT_DIRECTORY is set to /foo/bar then "git
           rev-parse --git-path objects/abc" returns /foo/bar/abc.

           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).

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

           Show the absolute path of the top-level directory of the working
           tree. If there is no working tree, report an error.

           Show the absolute path of the root of the superproject’s working tree
           (if exists) that uses the current repository as its submodule.
           Outputs nothing if the current repository is not used as a submodule
           by any project.

           Show the path to the shared index file in split index mode, or empty
           if not in split-index mode.

           Show the object format (hash algorithm) used for the repository for
           storage inside the .git directory, input, or output. For input,
           multiple algorithms may be printed, space-separated. If not
           specified, the default is "storage".

   Other Options
       --since=datestring, --after=datestring
           Parse the date string, and output the corresponding --max-age=
           parameter for git rev-list.

       --until=datestring, --before=datestring
           Parse the date string, and output the corresponding --min-age=
           parameter for git rev-list.

           Flags and parameters to be parsed.

       A revision parameter <rev> typically, but not necessarily, names a commit
       object. It uses what is called an extended SHA-1 syntax. Here are various
       ways to spell object names. The ones listed near the end of this list
       name trees and blobs contained in a commit.

           This document shows the "raw" syntax as seen by git. The shell and
           other UIs might require additional quoting to protect special
           characters and to avoid word splitting.

       <sha1>, e.g. dae86e1950b1277e545cee180551750029cfe735, dae86e
           The full SHA-1 object name (40-byte hexadecimal string), or a leading
           substring that is unique within the repository. E.g.
           dae86e1950b1277e545cee180551750029cfe735 and dae86e both name the
           same commit object if there is no other object in your repository
           whose object name starts with dae86e.

       <describeOutput>, e.g. v1.7.4.2-679-g3bee7fb
           Output from git describe; i.e. a closest tag, optionally followed by
           a dash and a number of commits, followed by a dash, a g, and an
           abbreviated object name.

       <refname>, e.g. master, heads/master, refs/heads/master
           A symbolic ref name. E.g.  master typically means the commit object
           referenced by 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. When ambiguous, a <refname> is
           disambiguated by taking the first match in the following rules:

            1. If $GIT_DIR/<refname> exists, that is what you mean (this is
               usually useful only for HEAD, FETCH_HEAD, ORIG_HEAD, MERGE_HEAD
               and CHERRY_PICK_HEAD);

            2. otherwise, refs/<refname> if it exists;

            3. otherwise, refs/tags/<refname> if it exists;

            4. otherwise, refs/heads/<refname> if it exists;

            5. otherwise, refs/remotes/<refname> if it exists;

            6. otherwise, refs/remotes/<refname>/HEAD if it exists.

               HEAD names the commit on which you based the changes in the
               working tree.  FETCH_HEAD records the branch which you fetched
               from a remote repository with your last git fetch invocation.
               ORIG_HEAD is created by commands that move your HEAD in a drastic
               way, to record the position of the HEAD before their operation,
               so that you can easily change the tip of the branch back to the
               state before you ran them.  MERGE_HEAD records the commit(s)
               which you are merging into your branch when you run git merge.
               CHERRY_PICK_HEAD records the commit which you are cherry-picking
               when you run git cherry-pick.

               Note that any of the refs/* cases above may come either from the
               $GIT_DIR/refs directory or from the $GIT_DIR/packed-refs file.
               While the ref name encoding is unspecified, UTF-8 is preferred as
               some output processing may assume ref names in UTF-8.

           @ alone is a shortcut for HEAD.

       [<refname>]@{<date>}, e.g. master@{yesterday}, HEAD@{5 minutes ago}
           A ref followed by the suffix @ with 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}) specifies 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>). Note that this looks up the state of your
           local ref at a given time; e.g., what was in your local master branch
           last week. If you want to look at commits made during certain times,
           see --since and --until.

       <refname>@{<n>}, e.g. master@{1}
           A ref followed by the suffix @ with an ordinal specification enclosed
           in a brace pair (e.g.  {1}, {15}) specifies the n-th prior value of
           that ref. For example master@{1} is the immediate prior value of
           master while master@{5} is the 5th prior value of master. This suffix
           may only be used immediately following a ref name and the ref must
           have an existing log ($GIT_DIR/logs/<refname>).

       @{<n>}, e.g. @{1}
           You can use the @ construct with an empty ref part to get at a reflog
           entry of the current branch. For example, if you are on branch blabla
           then @{1} means the same as blabla@{1}.

       @{-<n>}, e.g. @{-1}
           The construct @{-<n>} means the <n>th branch/commit checked out
           before the current one.

       [<branchname>]@{upstream}, e.g. master@{upstream}, @{u}
           The suffix @{upstream} to a branchname (short form <branchname>@{u})
           refers to the branch that the branch specified by branchname is set
           to build on top of (configured with branch.<name>.remote and
           branch.<name>.merge). A missing branchname defaults to the current
           one. These suffixes are also accepted when spelled in uppercase, and
           they mean the same thing no matter the case.

       [<branchname>]@{push}, e.g. master@{push}, @{push}
           The suffix @{push} reports the branch "where we would push to" if git
           push were run while branchname was checked out (or the current HEAD
           if no branchname is specified). Since our push destination is in a
           remote repository, of course, we report the local tracking branch
           that corresponds to that branch (i.e., something in refs/remotes/).

           Here’s an example to make it more clear:

               $ git config push.default current
               $ git config remote.pushdefault myfork
               $ git switch -c mybranch origin/master

               $ git rev-parse --symbolic-full-name @{upstream}

               $ git rev-parse --symbolic-full-name @{push}

           Note in the example that we set up a triangular workflow, where we
           pull from one location and push to another. In a non-triangular
           workflow, @{push} is the same as @{upstream}, and there is no need
           for it.

           This suffix is also accepted when spelled in uppercase, and means the
           same thing no matter the case.

       <rev>^[<n>], e.g. HEAD^, v1.5.1^0
           A suffix ^ to a revision parameter means the first parent of that
           commit object.  ^<n> means the <n>th parent (i.e.  <rev>^ is
           equivalent to <rev>^1). As a special rule, <rev>^0 means the commit
           itself and is used when <rev> is the object name of a tag object that
           refers to a commit object.

       <rev>~[<n>], e.g. HEAD~, master~3
           A suffix ~ to a revision parameter means the first parent of that
           commit object. A suffix ~<n> to a revision parameter means the commit
           object that is the <n>th generation ancestor of the named commit
           object, following only the first parents. I.e.  <rev>~3 is equivalent
           to <rev>^^^ which is equivalent to <rev>^1^1^1. See below for an
           illustration of the usage of this form.

       <rev>^{<type>}, e.g. v0.99.8^{commit}
           A suffix ^ followed by an object type name enclosed in brace pair
           means dereference the object at <rev> recursively until an object of
           type <type> is found or the object cannot be dereferenced anymore (in
           which case, barf). For example, if <rev> is a commit-ish,
           <rev>^{commit} describes the corresponding commit object. Similarly,
           if <rev> is a tree-ish, <rev>^{tree} describes the corresponding tree
           object.  <rev>^0 is a short-hand for <rev>^{commit}.

           <rev>^{object} can be used to make sure <rev> names an object that
           exists, without requiring <rev> to be a tag, and without
           dereferencing <rev>; because a tag is already an object, it does not
           have to be dereferenced even once to get to an object.

           <rev>^{tag} can be used to ensure that <rev> identifies an existing
           tag object.

       <rev>^{}, e.g. v0.99.8^{}
           A suffix ^ followed by an empty brace pair means the object could be
           a tag, and dereference the tag recursively until a non-tag object is

       <rev>^{/<text>}, e.g. HEAD^{/fix nasty bug}
           A suffix ^ to a revision parameter, followed by a brace pair that
           contains a text led by a slash, is the same as the :/fix nasty bug
           syntax below except that it returns the youngest matching commit
           which is reachable from the <rev> before ^.

       :/<text>, e.g. :/fix nasty bug
           A colon, followed by a slash, followed by a text, names a commit
           whose commit message matches the specified regular expression. This
           name returns the youngest matching commit which is reachable from any
           ref, including HEAD. The regular expression can match any part of the
           commit message. To match messages starting with a string, one can use
           e.g.  :/^foo. The special sequence :/!  is reserved for modifiers to
           what is matched.  :/!-foo performs a negative match, while :/!!foo
           matches a literal !  character, followed by foo. Any other sequence
           beginning with :/!  is reserved for now. Depending on the given text,
           the shell’s word splitting rules might require additional quoting.

       <rev>:<path>, e.g. HEAD:README, master:./README
           A suffix : followed by a path names the blob or tree at the given
           path in the tree-ish object named by the part before the colon. A
           path starting with ./ or ../ is relative to the current working
           directory. The given path will be converted to be relative to the
           working tree’s root directory. This is most useful to address a blob
           or tree from a commit or tree that has the same tree structure as the
           working tree.

       :[<n>:]<path>, e.g. :0:README, :README
           A colon, optionally followed by a stage number (0 to 3) and a colon,
           followed by a path, names a blob object in the index at the given
           path. A missing stage number (and the colon that follows it) names a
           stage 0 entry. During a merge, stage 1 is the common ancestor, stage
           2 is the target branch’s version (typically the current branch), and
           stage 3 is the version from the branch which is being merged.

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

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

           A =      = A^0
           B = A^   = A^1     = A~1
           C =      = 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

       History traversing commands such as git log operate on a set of commits,
       not just a single commit.

       For these commands, specifying a single revision, using the notation
       described in the previous section, means the set of commits reachable
       from the given commit.

       Specifying several revisions means the set of commits reachable from any
       of the given commits.

       A commit’s reachable set is the commit itself and the commits in its
       ancestry chain.

   Commit Exclusions
       ^<rev> (caret) Notation
           To exclude commits reachable from a commit, a prefix ^ notation is
           used. E.g.  ^r1 r2 means commits reachable from r2 but exclude the
           ones reachable from r1 (i.e.  r1 and its ancestors).

   Dotted Range Notations
       The .. (two-dot) Range Notation
           The ^r1 r2 set operation appears so often that there is a shorthand
           for it. When you have two commits r1 and r2 (named according to the
           syntax explained in SPECIFYING REVISIONS above), you can ask for
           commits that are reachable from r2 excluding those that are reachable
           from r1 by ^r1 r2 and it can be written as r1..r2.

       The ... (three-dot) Symmetric Difference Notation
           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 is
           the set of commits that are reachable from either one of r1 (left
           side) or r2 (right side) but not from both.

       In these two shorthand notations, you can omit one end and let it default
       to HEAD. For example, origin.. is a shorthand for origin..HEAD and asks
       "What did I do since I forked from the origin branch?" Similarly,
       ..origin is a shorthand for HEAD..origin and asks "What did the origin do
       since I forked from them?" Note that .. would mean HEAD..HEAD which is an
       empty range that is both reachable and unreachable from HEAD.

   Other <rev>^ Parent Shorthand Notations
       Three other shorthands exist, particularly useful for merge commits, for
       naming a set that is formed by a commit and its parent commits.

       The r1^@ notation means all parents of r1.

       The r1^! notation includes commit r1 but excludes all of its parents. By
       itself, this notation denotes the single commit r1.

       The <rev>^-[<n>] notation includes <rev> but excludes the <n>th parent
       (i.e. a shorthand for <rev>^<n>..<rev>), with <n> = 1 if not given. This
       is typically useful for merge commits where you can just pass <commit>^-
       to get all the commits in the branch that was merged in merge commit
       <commit> (including <commit> itself).

       While <rev>^<n> was about specifying a single commit parent, these three
       notations also consider its parents. For example you can say HEAD^2^@,
       however you cannot say HEAD^@^2.

           Include commits that are reachable from <rev> (i.e. <rev> and its

           Exclude commits that are reachable from <rev> (i.e. <rev> and its

           Include commits that are reachable from <rev2> but exclude those that
           are reachable from <rev1>. When either <rev1> or <rev2> is omitted,
           it defaults to HEAD.

           Include commits that are reachable from either <rev1> or <rev2> but
           exclude those that are reachable from both. When either <rev1> or
           <rev2> is omitted, it defaults to HEAD.

       <rev>^@, e.g. HEAD^@
           A suffix ^ followed by an at sign is the same as listing all parents
           of <rev> (meaning, include anything reachable from its parents, but
           not the commit itself).

       <rev>^!, e.g. HEAD^!
           A suffix ^ followed by an exclamation mark is the same as giving
           commit <rev> and then all its parents prefixed with ^ to exclude them
           (and their ancestors).

       <rev>^-<n>, e.g. HEAD^-, HEAD^-2
           Equivalent to <rev>^<n>..<rev>, with <n> = 1 if not given.

       Here are a handful of examples using the Loeliger illustration above,
       with each step in the notation’s expansion and selection carefully spelt

              Args   Expanded arguments    Selected commits
              D                            G H D
              D F                          G H I J D F
              ^G D                         H D
              ^D B                         E I J F B
              ^D B C                       E I J F B C
              C                            I J F C
              B..C   = ^B C                C
              B...C  = B ^F C              G H D E B C
              B^-    = B^..B
                     = ^B^1 B              E I J F B
              C^@    = C^1
                     = F                   I J F
              B^@    = B^1 B^2 B^3
                     = D E F               D G H E F I J
              C^!    = C ^C^@
                     = C ^C^1
                     = C ^F                C
              B^!    = B ^B^@
                     = B ^B^1 ^B^2 ^B^3
                     = B ^D ^E ^F          B
              F^! D  = F ^I ^J D           G H D F

       In --parseopt mode, git rev-parse helps massaging options to bring to
       shell scripts the same facilities C builtins have. It works as an option
       normalizer (e.g. splits single switches aggregate values), a bit like
       getopt(1) does.

       It takes on the standard input the specification of the options to parse
       and understand, and echoes on the standard output a string suitable for
       sh(1) eval to replace the arguments with normalized ones. In case of
       error, it outputs usage on the standard error stream, and exits with code

       Note: Make sure you quote the result when passing it to eval. See below
       for an example.

   Input Format
       git rev-parse --parseopt input format is fully text based. It has two
       parts, separated by a line that contains only --. The lines before the
       separator (should be one or more) are used for the usage. The lines after
       the separator describe the options.

       Each line of options has this format:

           <opt-spec><flags>*<arg-hint>? SP+ help LF

           its format is the short option character, then the long option name
           separated by a comma. Both parts are not required, though at least
           one is necessary. May not contain any of the <flags> characters.
           h,help, dry-run and f are examples of correct <opt-spec>.

           <flags> are of *, =, ?  or !.

           •   Use = if the option takes an argument.

           •   Use ?  to mean that the option takes an optional argument. You
               probably want to use the --stuck-long mode to be able to
               unambiguously parse the optional argument.

           •   Use * to mean that this option should not be listed in the usage
               generated for the -h argument. It’s shown for --help-all as
               documented in gitcli(7).

           •   Use !  to not make the corresponding negated long option

           <arg-hint>, if specified, is used as a name of the argument in the
           help output, for options that take arguments.  <arg-hint> is
           terminated by the first whitespace. It is customary to use a dash to
           separate words in a multi-word argument hint.

       The remainder of the line, after stripping the spaces, is used as the
       help associated to the option.

       Blank lines are ignored, and lines that don’t match this specification
       are used as option group headers (start the line with a space to create
       such lines on purpose).

           some-command [<options>] <args>...

           some-command does foo and bar!
           h,help    show the help

           foo       some nifty option --foo
           bar=      some cool option --bar with an argument
           baz=arg   another cool option --baz with a named argument
           qux?path  qux may take a path argument but has meaning by itself

             An option group Header
           C?        option C with an optional argument"

           eval "$(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)"

   Usage text
       When "$@" is -h or --help in the above example, the following usage text
       would be shown:

           usage: some-command [<options>] <args>...

               some-command does foo and bar!

               -h, --help            show the help
               --foo                 some nifty option --foo
               --bar ...             some cool option --bar with an argument
               --baz <arg>           another cool option --baz with a named argument
               --qux[=<path>]        qux may take a path argument but has meaning by itself

           An option group Header
               -C[...]               option C with an optional argument

       In --sq-quote mode, git rev-parse echoes on the standard output a single
       line suitable for sh(1) eval. This line is made by normalizing the
       arguments following --sq-quote. Nothing other than quoting the arguments
       is done.

       If you want command input to still be interpreted as usual by git
       rev-parse before the output is shell quoted, see the --sq option.

           $ cat > <<\EOF
           args=$(git rev-parse --sq-quote "$@")   # quote user-supplied arguments
           command="git frotz -n24 $args"          # and use it inside a handcrafted
                                                   # command line
           eval "$command"

           $ sh "a b'c"

       •   Print the object name of the current commit:

               $ git rev-parse --verify HEAD

       •   Print the commit object name from the revision in the $REV shell

               $ git rev-parse --verify --end-of-options $REV^{commit}

           This will error out if $REV is empty or not a valid revision.

       •   Similar to above:

               $ git rev-parse --default master --verify --end-of-options $REV

           but if $REV is empty, the commit object name from master will be

       Part of the git(1) suite

Git 2.30.0                         12/28/2020                   GIT-REV-PARSE(1)