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git-commit-vandalism/Documentation/git-rev-parse.txt
Jeff King 3a1f91cfd9 rev-parse: handle --end-of-options 
We taught rev-list a new way to separate options from revisions in
19e8789b23 (revision: allow --end-of-options to end option parsing,
2019-08-06), but rev-parse uses its own parser. It should know about
--end-of-options not only for consistency, but because it may be
presented with similarly ambiguous cases. E.g., if a caller does:

  git rev-parse "$rev" -- "$path"

to parse an untrusted input, then it will get confused if $rev contains
an option-like string like "--local-env-vars". Or even "--not-real",
which we'd keep as an option to pass along to rev-list.

Or even more importantly:

  git rev-parse --verify "$rev"

can be confused by options, even though its purpose is safely parsing
untrusted input. On the plus side, it will always fail the --verify
part, as it will not have parsed a revision, so the caller will
generally "fail closed" rather than continue to use the untrusted
string. But it will still trigger whatever option was in "$rev"; this
should be mostly harmless, since rev-parse options are all read-only,
but I didn't carefully audit all paths.

This patch lets callers write:

  git rev-parse --end-of-options "$rev" -- "$path"

and:

  git rev-parse --verify --end-of-options "$rev"

which will both treat "$rev" always as a revision parameter. The latter
is a bit clunky. It would be nicer if we had defined "--verify" to
require that its next argument be the revision. But we have not
historically done so, and:

  git rev-parse --verify -q "$rev"

does currently work. I added a test here to confirm that we didn't break
that.

A few implementation notes:

 - We don't document --end-of-options explicitly in commands, but rather
   in gitcli(7). So I didn't give it its own section in git-rev-parse(1).
   But I did call it out specifically in the --verify section, and
   include it in the examples, which should show best practices.

 - We don't have to re-indent the main option-parsing block, because we
   can combine our "did we see end of options" check with "does it start
   with a dash". The exception is the pre-setup options, which need
   their own block.

 - We do however have to pull the "--" parsing out of the "does it start
   with dash" block, because we want to parse it even if we've seen
   --end-of-options.

 - We'll leave "--end-of-options" in the output. This is probably not
   technically necessary, as a careful caller will do:

     git rev-parse --end-of-options $revs -- $paths

   and anything in $revs will be resolved to an object id. However, it
   does help a slightly less careful caller like:

     git rev-parse --end-of-options $revs_or_paths

   where a path "--foo" will remain in the output as long as it also
   exists on disk. In that case, it's helpful to retain --end-of-options
   to get passed along to rev-list, s it would otherwise see just
   "--foo".

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-10 13:46:27 -08:00

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git-rev-parse(1)
================
NAME
----
git-rev-parse - Pick out and massage parameters
SYNOPSIS
--------
[verse]
'git rev-parse' [<options>] <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
-------
Operation Modes
~~~~~~~~~~~~~~~
Each of these options must appear first on the command line.
--parseopt::
Use 'git rev-parse' in option parsing mode (see PARSEOPT section below).
--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.
Options for --parseopt
~~~~~~~~~~~~~~~~~~~~~~
--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.
--stuck-long::
Only meaningful in `--parseopt` mode. Output the options in their
long form if available, and with their arguments stuck.
Options for Filtering
~~~~~~~~~~~~~~~~~~~~~
--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.
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" -- "$@")"
----
--verify::
Verify that exactly one parameter is provided, and that it
can be turned into a raw 20-byte SHA-1 that can be used to
access the object database. If so, emit it to the standard
output; otherwise, error out.
+
If you want to make sure that the output actually names an object in
your object database and/or can be used as a specific type of object
you require, you can add the `^{type}` peeling operator to the parameter.
For example, `git rev-parse "$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.
--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.
--short[=length]::
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 linkgit:git-config[1]).
--not::
When showing object names, prefix them with '{caret}' and
strip '{caret}' prefix from the object names that already have
one.
--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.
--symbolic::
Usually the object names are output in SHA-1 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").
Options for Objects
~~~~~~~~~~~~~~~~~~~
--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 `/*`.
--exclude=<glob-pattern>::
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 '/{asterisk}' is intended, it must be given
explicitly.
--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.
Options for Files
~~~~~~~~~~~~~~~~~
--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.
--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 `$GIT_DIR` is not defined and the current directory
is not detected to lie in a Git repository or work tree
print a message to stderr and exit with nonzero status.
--absolute-git-dir::
Like `--git-dir`, but its output is always the canonicalized
absolute path.
--git-common-dir::
Show `$GIT_COMMON_DIR` if defined, else `$GIT_DIR`.
--is-inside-git-dir::
When the current working directory is below the repository
directory print "true", otherwise "false".
--is-inside-work-tree::
When the current working directory is inside the work tree of the
repository print "true", otherwise "false".
--is-bare-repository::
When the repository is bare print "true", otherwise "false".
--is-shallow-repository::
When the repository is shallow print "true", otherwise "false".
--resolve-git-dir <path>::
Check if <path> is a valid repository or a gitfile that
points at a valid repository, and print the location of the
repository. If <path> is a gitfile then the resolved path
to the real repository is printed.
--git-path <path>::
Resolve "$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.
--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).
--show-prefix::
When the command is invoked from a subdirectory, show the
path of the current directory relative to the top-level
directory.
--show-toplevel::
Show the absolute path of the top-level directory of the working
tree. If there is no working tree, report an error.
--show-superproject-working-tree::
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.
--shared-index-path::
Show the path to the shared index file in split index mode, or
empty if not in split-index mode.
--show-object-format[=(storage|input|output)]::
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'.
<args>...::
Flags and parameters to be parsed.
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 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
------------
`<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. May not contain any of the `<flags>` characters.
`h,help`, `dry-run` and `f` are examples of correct `<opt-spec>`.
`<flags>`::
`<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 linkgit:gitcli[7].
* Use `!` to not make the corresponding negated long option available.
`<arg-hint>`::
`<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).
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
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
------------
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 --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 printed.
GIT
---
Part of the linkgit:git[1] suite
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