glossary: improve description of SHA-1 related topics

[thirdparty/git.git] / Documentation / git-rev-parse.txt

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

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


SYNOPSIS
--------
[verse]
'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 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.


OPTIONS
-------
--parseopt::
	Use 'git rev-parse' in option parsing mode (see PARSEOPT section below).

--keep-dashdash::
	Only meaningful in `--parseopt` mode. Tells the option parser to echo
	out the first `--` met instead of skipping it.

--stop-at-non-option::
	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.

--sq-quote::
	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.

--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.

-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.

--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-{asterisk}'). In contrast to the `--sq-quote` option,
	the command input is still interpreted as usual.

--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.

--symbolic-full-name::
	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").

--abbrev-ref[=(strict|loose)]::
	A non-ambiguous short name of the objects name.
	The option core.warnAmbiguousRefs is used to select the strict
	abbreviation mode.

--disambiguate=<prefix>::
	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.

--all::
	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`, respectively).
+
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 `/*`.

--glob=pattern::
	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 `/*`.

--show-toplevel::
	Show the absolute path of the top-level directory.

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

--is-inside-git-dir::
	When the current working directory is below the repository
	directory print "true", otherwise "false".

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

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

--local-env-vars::
	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.

--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::
	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'.

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

--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 printed.


include::revisions.txt[]

PARSEOPT
--------

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 129.

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 more than one) are used for the usage.
The lines after the separator describe the options.

Each line of options has this format:

------------
<opt_spec><flags>* SP+ help LF
------------

`<opt_spec>`::
	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. `h,help`, `dry-run` and `f` are all three correct
	`<opt_spec>`.

`<flags>`::
	`<flags>` are of `*`, `=`, `?` or `!`.
	* Use `=` if the option takes an argument.

	* Use `?` to mean that the option is optional (though its use is discouraged).

	* 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 linkgit:gitcli[7].

	* Use `!` to not make the corresponding negated long option available.

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).

Example
~~~~~~~

------------
OPTS_SPEC="\
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

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

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

SQ-QUOTE
--------

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.

Example
~~~~~~~

------------
$ cat >your-git-script.sh <<\EOF
#!/bin/sh
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"
EOF

$ sh your-git-script.sh "a b'c"
------------

EXAMPLES
--------

* 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 variable:
+
------------
$ git rev-parse --verify $REV
------------
+
This will error out if $REV is empty or not a valid revision.

* Same as above:
+
------------
$ git rev-parse --default master --verify $REV
------------
+
but if $REV is empty, the commit object name from master will be printed.

GIT
---
Part of the linkgit:git[1] suite