merge(third_party/git): Merge squashed git subtree at v2.23.0 r/373

Merge commit '1b593e1ea4d2af0f6444d9a7788d5d99abd6fde5' as 'third_party/git'

1 files changed, 1730 insertions, 0 deletions

diff --git a/third_party/git/perl/Git.pm b/third_party/git/perl/Git.pm
new file mode 100644
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+++ b/third_party/git/perl/Git.pm
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+=head1 NAME
+
+Git - Perl interface to the Git version control system
+
+=cut
+
+
+package Git;
+
+use 5.008;
+use strict;
+use warnings;
+
+use File::Temp ();
+use File::Spec ();
+
+BEGIN {
+
+our ($VERSION, @ISA, @EXPORT, @EXPORT_OK);
+
+# Totally unstable API.
+$VERSION = '0.01';
+
+
+=head1 SYNOPSIS
+
+  use Git;
+
+  my $version = Git::command_oneline('version');
+
+  git_cmd_try { Git::command_noisy('update-server-info') }
+              '%s failed w/ code %d';
+
+  my $repo = Git->repository (Directory => '/srv/git/cogito.git');
+
+
+  my @revs = $repo->command('rev-list', '--since=last monday', '--all');
+
+  my ($fh, $c) = $repo->command_output_pipe('rev-list', '--since=last monday', '--all');
+  my $lastrev = <$fh>; chomp $lastrev;
+  $repo->command_close_pipe($fh, $c);
+
+  my $lastrev = $repo->command_oneline( [ 'rev-list', '--all' ],
+                                        STDERR => 0 );
+
+  my $sha1 = $repo->hash_and_insert_object('file.txt');
+  my $tempfile = tempfile();
+  my $size = $repo->cat_blob($sha1, $tempfile);
+
+=cut
+
+
+require Exporter;
+
+@ISA = qw(Exporter);
+
+@EXPORT = qw(git_cmd_try);
+
+# Methods which can be called as standalone functions as well:
+@EXPORT_OK = qw(command command_oneline command_noisy
+                command_output_pipe command_input_pipe command_close_pipe
+                command_bidi_pipe command_close_bidi_pipe
+                version exec_path html_path hash_object git_cmd_try
+                remote_refs prompt
+                get_tz_offset get_record
+                credential credential_read credential_write
+                temp_acquire temp_is_locked temp_release temp_reset temp_path
+                unquote_path);
+
+
+=head1 DESCRIPTION
+
+This module provides Perl scripts easy way to interface the Git version control
+system. The modules have an easy and well-tested way to call arbitrary Git
+commands; in the future, the interface will also provide specialized methods
+for doing easily operations which are not totally trivial to do over
+the generic command interface.
+
+While some commands can be executed outside of any context (e.g. 'version'
+or 'init'), most operations require a repository context, which in practice
+means getting an instance of the Git object using the repository() constructor.
+(In the future, we will also get a new_repository() constructor.) All commands
+called as methods of the object are then executed in the context of the
+repository.
+
+Part of the "repository state" is also information about path to the attached
+working copy (unless you work with a bare repository). You can also navigate
+inside of the working copy using the C<wc_chdir()> method. (Note that
+the repository object is self-contained and will not change working directory
+of your process.)
+
+TODO: In the future, we might also do
+
+	my $remoterepo = $repo->remote_repository (Name => 'cogito', Branch => 'master');
+	$remoterepo ||= Git->remote_repository ('http://git.or.cz/cogito.git/');
+	my @refs = $remoterepo->refs();
+
+Currently, the module merely wraps calls to external Git tools. In the future,
+it will provide a much faster way to interact with Git by linking directly
+to libgit. This should be completely opaque to the user, though (performance
+increase notwithstanding).
+
+=cut
+
+
+use Carp qw(carp croak); # but croak is bad - throw instead
+use Git::LoadCPAN::Error qw(:try);
+use Cwd qw(abs_path cwd);
+use IPC::Open2 qw(open2);
+use Fcntl qw(SEEK_SET SEEK_CUR);
+use Time::Local qw(timegm);
+}
+
+
+=head1 CONSTRUCTORS
+
+=over 4
+
+=item repository ( OPTIONS )
+
+=item repository ( DIRECTORY )
+
+=item repository ()
+
+Construct a new repository object.
+C<OPTIONS> are passed in a hash like fashion, using key and value pairs.
+Possible options are:
+
+B<Repository> - Path to the Git repository.
+
+B<WorkingCopy> - Path to the associated working copy; not strictly required
+as many commands will happily crunch on a bare repository.
+
+B<WorkingSubdir> - Subdirectory in the working copy to work inside.
+Just left undefined if you do not want to limit the scope of operations.
+
+B<Directory> - Path to the Git working directory in its usual setup.
+The C<.git> directory is searched in the directory and all the parent
+directories; if found, C<WorkingCopy> is set to the directory containing
+it and C<Repository> to the C<.git> directory itself. If no C<.git>
+directory was found, the C<Directory> is assumed to be a bare repository,
+C<Repository> is set to point at it and C<WorkingCopy> is left undefined.
+If the C<$GIT_DIR> environment variable is set, things behave as expected
+as well.
+
+You should not use both C<Directory> and either of C<Repository> and
+C<WorkingCopy> - the results of that are undefined.
+
+Alternatively, a directory path may be passed as a single scalar argument
+to the constructor; it is equivalent to setting only the C<Directory> option
+field.
+
+Calling the constructor with no options whatsoever is equivalent to
+calling it with C<< Directory => '.' >>. In general, if you are building
+a standard porcelain command, simply doing C<< Git->repository() >> should
+do the right thing and setup the object to reflect exactly where the user
+is right now.
+
+=cut
+
+sub repository {
+	my $class = shift;
+	my @args = @_;
+	my %opts = ();
+	my $self;
+
+	if (defined $args[0]) {
+		if ($#args % 2 != 1) {
+			# Not a hash.
+			$#args == 0 or throw Error::Simple("bad usage");
+			%opts = ( Directory => $args[0] );
+		} else {
+			%opts = @args;
+		}
+	}
+
+	if (not defined $opts{Repository} and not defined $opts{WorkingCopy}
+		and not defined $opts{Directory}) {
+		$opts{Directory} = '.';
+	}
+
+	if (defined $opts{Directory}) {
+		-d $opts{Directory} or throw Error::Simple("Directory not found: $opts{Directory} $!");
+
+		my $search = Git->repository(WorkingCopy => $opts{Directory});
+		my $dir;
+		try {
+			$dir = $search->command_oneline(['rev-parse', '--git-dir'],
+			                                STDERR => 0);
+		} catch Git::Error::Command with {
+			$dir = undef;
+		};
+
+		if ($dir) {
+			File::Spec->file_name_is_absolute($dir) or $dir = $opts{Directory} . '/' . $dir;
+			$opts{Repository} = abs_path($dir);
+
+			# If --git-dir went ok, this shouldn't die either.
+			my $prefix = $search->command_oneline('rev-parse', '--show-prefix');
+			$dir = abs_path($opts{Directory}) . '/';
+			if ($prefix) {
+				if (substr($dir, -length($prefix)) ne $prefix) {
+					throw Error::Simple("rev-parse confused me - $dir does not have trailing $prefix");
+				}
+				substr($dir, -length($prefix)) = '';
+			}
+			$opts{WorkingCopy} = $dir;
+			$opts{WorkingSubdir} = $prefix;
+
+		} else {
+			# A bare repository? Let's see...
+			$dir = $opts{Directory};
+
+			unless (-d "$dir/refs" and -d "$dir/objects" and -e "$dir/HEAD") {
+				# Mimic git-rev-parse --git-dir error message:
+				throw Error::Simple("fatal: Not a git repository: $dir");
+			}
+			my $search = Git->repository(Repository => $dir);
+			try {
+				$search->command('symbolic-ref', 'HEAD');
+			} catch Git::Error::Command with {
+				# Mimic git-rev-parse --git-dir error message:
+				throw Error::Simple("fatal: Not a git repository: $dir");
+			}
+
+			$opts{Repository} = abs_path($dir);
+		}
+
+		delete $opts{Directory};
+	}
+
+	$self = { opts => \%opts };
+	bless $self, $class;
+}
+
+=back
+
+=head1 METHODS
+
+=over 4
+
+=item command ( COMMAND [, ARGUMENTS... ] )
+
+=item command ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
+
+Execute the given Git C<COMMAND> (specify it without the 'git-'
+prefix), optionally with the specified extra C<ARGUMENTS>.
+
+The second more elaborate form can be used if you want to further adjust
+the command execution. Currently, only one option is supported:
+
+B<STDERR> - How to deal with the command's error output. By default (C<undef>)
+it is delivered to the caller's C<STDERR>. A false value (0 or '') will cause
+it to be thrown away. If you want to process it, you can get it in a filehandle
+you specify, but you must be extremely careful; if the error output is not
+very short and you want to read it in the same process as where you called
+C<command()>, you are set up for a nice deadlock!
+
+The method can be called without any instance or on a specified Git repository
+(in that case the command will be run in the repository context).
+
+In scalar context, it returns all the command output in a single string
+(verbatim).
+
+In array context, it returns an array containing lines printed to the
+command's stdout (without trailing newlines).
+
+In both cases, the command's stdin and stderr are the same as the caller's.
+
+=cut
+
+sub command {
+	my ($fh, $ctx) = command_output_pipe(@_);
+
+	if (not defined wantarray) {
+		# Nothing to pepper the possible exception with.
+		_cmd_close($ctx, $fh);
+
+	} elsif (not wantarray) {
+		local $/;
+		my $text = <$fh>;
+		try {
+			_cmd_close($ctx, $fh);
+		} catch Git::Error::Command with {
+			# Pepper with the output:
+			my $E = shift;
+			$E->{'-outputref'} = \$text;
+			throw $E;
+		};
+		return $text;
+
+	} else {
+		my @lines = <$fh>;
+		defined and chomp for @lines;
+		try {
+			_cmd_close($ctx, $fh);
+		} catch Git::Error::Command with {
+			my $E = shift;
+			$E->{'-outputref'} = \@lines;
+			throw $E;
+		};
+		return @lines;
+	}
+}
+
+
+=item command_oneline ( COMMAND [, ARGUMENTS... ] )
+
+=item command_oneline ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
+
+Execute the given C<COMMAND> in the same way as command()
+does but always return a scalar string containing the first line
+of the command's standard output.
+
+=cut
+
+sub command_oneline {
+	my ($fh, $ctx) = command_output_pipe(@_);
+
+	my $line = <$fh>;
+	defined $line and chomp $line;
+	try {
+		_cmd_close($ctx, $fh);
+	} catch Git::Error::Command with {
+		# Pepper with the output:
+		my $E = shift;
+		$E->{'-outputref'} = \$line;
+		throw $E;
+	};
+	return $line;
+}
+
+
+=item command_output_pipe ( COMMAND [, ARGUMENTS... ] )
+
+=item command_output_pipe ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
+
+Execute the given C<COMMAND> in the same way as command()
+does but return a pipe filehandle from which the command output can be
+read.
+
+The function can return C<($pipe, $ctx)> in array context.
+See C<command_close_pipe()> for details.
+
+=cut
+
+sub command_output_pipe {
+	_command_common_pipe('-|', @_);
+}
+
+
+=item command_input_pipe ( COMMAND [, ARGUMENTS... ] )
+
+=item command_input_pipe ( [ COMMAND, ARGUMENTS... ], { Opt => Val ... } )
+
+Execute the given C<COMMAND> in the same way as command_output_pipe()
+does but return an input pipe filehandle instead; the command output
+is not captured.
+
+The function can return C<($pipe, $ctx)> in array context.
+See C<command_close_pipe()> for details.
+
+=cut
+
+sub command_input_pipe {
+	_command_common_pipe('|-', @_);
+}
+
+
+=item command_close_pipe ( PIPE [, CTX ] )
+
+Close the C<PIPE> as returned from C<command_*_pipe()>, checking
+whether the command finished successfully. The optional C<CTX> argument
+is required if you want to see the command name in the error message,
+and it is the second value returned by C<command_*_pipe()> when
+called in array context. The call idiom is:
+
+	my ($fh, $ctx) = $r->command_output_pipe('status');
+	while (<$fh>) { ... }
+	$r->command_close_pipe($fh, $ctx);
+
+Note that you should not rely on whatever actually is in C<CTX>;
+currently it is simply the command name but in future the context might
+have more complicated structure.
+
+=cut
+
+sub command_close_pipe {
+	my ($self, $fh, $ctx) = _maybe_self(@_);
+	$ctx ||= '<unknown>';
+	_cmd_close($ctx, $fh);
+}
+
+=item command_bidi_pipe ( COMMAND [, ARGUMENTS... ] )
+
+Execute the given C<COMMAND> in the same way as command_output_pipe()
+does but return both an input pipe filehandle and an output pipe filehandle.
+
+The function will return C<($pid, $pipe_in, $pipe_out, $ctx)>.
+See C<command_close_bidi_pipe()> for details.
+
+=cut
+
+sub command_bidi_pipe {
+	my ($pid, $in, $out);
+	my ($self) = _maybe_self(@_);
+	local %ENV = %ENV;
+	my $cwd_save = undef;
+	if ($self) {
+		shift;
+		$cwd_save = cwd();
+		_setup_git_cmd_env($self);
+	}
+	$pid = open2($in, $out, 'git', @_);
+	chdir($cwd_save) if $cwd_save;
+	return ($pid, $in, $out, join(' ', @_));
+}
+
+=item command_close_bidi_pipe ( PID, PIPE_IN, PIPE_OUT [, CTX] )
+
+Close the C<PIPE_IN> and C<PIPE_OUT> as returned from C<command_bidi_pipe()>,
+checking whether the command finished successfully. The optional C<CTX>
+argument is required if you want to see the command name in the error message,
+and it is the fourth value returned by C<command_bidi_pipe()>.  The call idiom
+is:
+
+	my ($pid, $in, $out, $ctx) = $r->command_bidi_pipe('cat-file --batch-check');
+	print $out "000000000\n";
+	while (<$in>) { ... }
+	$r->command_close_bidi_pipe($pid, $in, $out, $ctx);
+
+Note that you should not rely on whatever actually is in C<CTX>;
+currently it is simply the command name but in future the context might
+have more complicated structure.
+
+C<PIPE_IN> and C<PIPE_OUT> may be C<undef> if they have been closed prior to
+calling this function.  This may be useful in a query-response type of
+commands where caller first writes a query and later reads response, eg:
+
+	my ($pid, $in, $out, $ctx) = $r->command_bidi_pipe('cat-file --batch-check');
+	print $out "000000000\n";
+	close $out;
+	while (<$in>) { ... }
+	$r->command_close_bidi_pipe($pid, $in, undef, $ctx);
+
+This idiom may prevent potential dead locks caused by data sent to the output
+pipe not being flushed and thus not reaching the executed command.
+
+=cut
+
+sub command_close_bidi_pipe {
+	local $?;
+	my ($self, $pid, $in, $out, $ctx) = _maybe_self(@_);
+	_cmd_close($ctx, (grep { defined } ($in, $out)));
+	waitpid $pid, 0;
+	if ($? >> 8) {
+		throw Git::Error::Command($ctx, $? >>8);
+	}
+}
+
+
+=item command_noisy ( COMMAND [, ARGUMENTS... ] )
+
+Execute the given C<COMMAND> in the same way as command() does but do not
+capture the command output - the standard output is not redirected and goes
+to the standard output of the caller application.
+
+While the method is called command_noisy(), you might want to as well use
+it for the most silent Git commands which you know will never pollute your
+stdout but you want to avoid the overhead of the pipe setup when calling them.
+
+The function returns only after the command has finished running.
+
+=cut
+
+sub command_noisy {
+	my ($self, $cmd, @args) = _maybe_self(@_);
+	_check_valid_cmd($cmd);
+
+	my $pid = fork;
+	if (not defined $pid) {
+		throw Error::Simple("fork failed: $!");
+	} elsif ($pid == 0) {
+		_cmd_exec($self, $cmd, @args);
+	}
+	if (waitpid($pid, 0) > 0 and $?>>8 != 0) {
+		throw Git::Error::Command(join(' ', $cmd, @args), $? >> 8);
+	}
+}
+
+
+=item version ()
+
+Return the Git version in use.
+
+=cut
+
+sub version {
+	my $verstr = command_oneline('--version');
+	$verstr =~ s/^git version //;
+	$verstr;
+}
+
+
+=item exec_path ()
+
+Return path to the Git sub-command executables (the same as
+C<git --exec-path>). Useful mostly only internally.
+
+=cut
+
+sub exec_path { command_oneline('--exec-path') }
+
+
+=item html_path ()
+
+Return path to the Git html documentation (the same as
+C<git --html-path>). Useful mostly only internally.
+
+=cut
+
+sub html_path { command_oneline('--html-path') }
+
+
+=item get_tz_offset ( TIME )
+
+Return the time zone offset from GMT in the form +/-HHMM where HH is
+the number of hours from GMT and MM is the number of minutes.  This is
+the equivalent of what strftime("%z", ...) would provide on a GNU
+platform.
+
+If TIME is not supplied, the current local time is used.
+
+=cut
+
+sub get_tz_offset {
+	# some systems don't handle or mishandle %z, so be creative.
+	my $t = shift || time;
+	my @t = localtime($t);
+	$t[5] += 1900;
+	my $gm = timegm(@t);
+	my $sign = qw( + + - )[ $gm <=> $t ];
+	return sprintf("%s%02d%02d", $sign, (gmtime(abs($t - $gm)))[2,1]);
+}
+
+=item get_record ( FILEHANDLE, INPUT_RECORD_SEPARATOR )
+
+Read one record from FILEHANDLE delimited by INPUT_RECORD_SEPARATOR,
+removing any trailing INPUT_RECORD_SEPARATOR.
+
+=cut
+
+sub get_record {
+	my ($fh, $rs) = @_;
+	local $/ = $rs;
+	my $rec = <$fh>;
+	chomp $rec if defined $rec;
+	$rec;
+}
+
+=item prompt ( PROMPT , ISPASSWORD  )
+
+Query user C<PROMPT> and return answer from user.
+
+Honours GIT_ASKPASS and SSH_ASKPASS environment variables for querying
+the user. If no *_ASKPASS variable is set or an error occoured,
+the terminal is tried as a fallback.
+If C<ISPASSWORD> is set and true, the terminal disables echo.
+
+=cut
+
+sub prompt {
+	my ($prompt, $isPassword) = @_;
+	my $ret;
+	if (exists $ENV{'GIT_ASKPASS'}) {
+		$ret = _prompt($ENV{'GIT_ASKPASS'}, $prompt);
+	}
+	if (!defined $ret && exists $ENV{'SSH_ASKPASS'}) {
+		$ret = _prompt($ENV{'SSH_ASKPASS'}, $prompt);
+	}
+	if (!defined $ret) {
+		print STDERR $prompt;
+		STDERR->flush;
+		if (defined $isPassword && $isPassword) {
+			require Term::ReadKey;
+			Term::ReadKey::ReadMode('noecho');
+			$ret = '';
+			while (defined(my $key = Term::ReadKey::ReadKey(0))) {
+				last if $key =~ /[\012\015]/; # \n\r
+				$ret .= $key;
+			}
+			Term::ReadKey::ReadMode('restore');
+			print STDERR "\n";
+			STDERR->flush;
+		} else {
+			chomp($ret = <STDIN>);
+		}
+	}
+	return $ret;
+}
+
+sub _prompt {
+	my ($askpass, $prompt) = @_;
+	return unless length $askpass;
+	$prompt =~ s/\n/ /g;
+	my $ret;
+	open my $fh, "-|", $askpass, $prompt or return;
+	$ret = <$fh>;
+	$ret =~ s/[\015\012]//g; # strip \r\n, chomp does not work on all systems (i.e. windows) as expected
+	close ($fh);
+	return $ret;
+}
+
+=item repo_path ()
+
+Return path to the git repository. Must be called on a repository instance.
+
+=cut
+
+sub repo_path { $_[0]->{opts}->{Repository} }
+
+
+=item wc_path ()
+
+Return path to the working copy. Must be called on a repository instance.
+
+=cut
+
+sub wc_path { $_[0]->{opts}->{WorkingCopy} }
+
+
+=item wc_subdir ()
+
+Return path to the subdirectory inside of a working copy. Must be called
+on a repository instance.
+
+=cut
+
+sub wc_subdir { $_[0]->{opts}->{WorkingSubdir} ||= '' }
+
+
+=item wc_chdir ( SUBDIR )
+
+Change the working copy subdirectory to work within. The C<SUBDIR> is
+relative to the working copy root directory (not the current subdirectory).
+Must be called on a repository instance attached to a working copy
+and the directory must exist.
+
+=cut
+
+sub wc_chdir {
+	my ($self, $subdir) = @_;
+	$self->wc_path()
+		or throw Error::Simple("bare repository");
+
+	-d $self->wc_path().'/'.$subdir
+		or throw Error::Simple("subdir not found: $subdir $!");
+	# Of course we will not "hold" the subdirectory so anyone
+	# can delete it now and we will never know. But at least we tried.
+
+	$self->{opts}->{WorkingSubdir} = $subdir;
+}
+
+
+=item config ( VARIABLE )
+
+Retrieve the configuration C<VARIABLE> in the same manner as C<config>
+does. In scalar context requires the variable to be set only one time
+(exception is thrown otherwise), in array context returns allows the
+variable to be set multiple times and returns all the values.
+
+=cut
+
+sub config {
+	return _config_common({}, @_);
+}
+
+
+=item config_bool ( VARIABLE )
+
+Retrieve the bool configuration C<VARIABLE>. The return value
+is usable as a boolean in perl (and C<undef> if it's not defined,
+of course).
+
+=cut
+
+sub config_bool {
+	my $val = scalar _config_common({'kind' => '--bool'}, @_);
+
+	# Do not rewrite this as return (defined $val && $val eq 'true')
+	# as some callers do care what kind of falsehood they receive.
+	if (!defined $val) {
+		return undef;
+	} else {
+		return $val eq 'true';
+	}
+}
+
+
+=item config_path ( VARIABLE )
+
+Retrieve the path configuration C<VARIABLE>. The return value
+is an expanded path or C<undef> if it's not defined.
+
+=cut
+
+sub config_path {
+	return _config_common({'kind' => '--path'}, @_);
+}
+
+
+=item config_int ( VARIABLE )
+
+Retrieve the integer configuration C<VARIABLE>. The return value
+is simple decimal number.  An optional value suffix of 'k', 'm',
+or 'g' in the config file will cause the value to be multiplied
+by 1024, 1048576 (1024^2), or 1073741824 (1024^3) prior to output.
+It would return C<undef> if configuration variable is not defined.
+
+=cut
+
+sub config_int {
+	return scalar _config_common({'kind' => '--int'}, @_);
+}
+
+# Common subroutine to implement bulk of what the config* family of methods
+# do. This currently wraps command('config') so it is not so fast.
+sub _config_common {
+	my ($opts) = shift @_;
+	my ($self, $var) = _maybe_self(@_);
+
+	try {
+		my @cmd = ('config', $opts->{'kind'} ? $opts->{'kind'} : ());
+		unshift @cmd, $self if $self;
+		if (wantarray) {
+			return command(@cmd, '--get-all', $var);
+		} else {
+			return command_oneline(@cmd, '--get', $var);
+		}
+	} catch Git::Error::Command with {
+		my $E = shift;
+		if ($E->value() == 1) {
+			# Key not found.
+			return;
+		} else {
+			throw $E;
+		}
+	};
+}
+
+=item get_colorbool ( NAME )
+
+Finds if color should be used for NAMEd operation from the configuration,
+and returns boolean (true for "use color", false for "do not use color").
+
+=cut
+
+sub get_colorbool {
+	my ($self, $var) = @_;
+	my $stdout_to_tty = (-t STDOUT) ? "true" : "false";
+	my $use_color = $self->command_oneline('config', '--get-colorbool',
+					       $var, $stdout_to_tty);
+	return ($use_color eq 'true');
+}
+
+=item get_color ( SLOT, COLOR )
+
+Finds color for SLOT from the configuration, while defaulting to COLOR,
+and returns the ANSI color escape sequence:
+
+	print $repo->get_color("color.interactive.prompt", "underline blue white");
+	print "some text";
+	print $repo->get_color("", "normal");
+
+=cut
+
+sub get_color {
+	my ($self, $slot, $default) = @_;
+	my $color = $self->command_oneline('config', '--get-color', $slot, $default);
+	if (!defined $color) {
+		$color = "";
+	}
+	return $color;
+}
+
+=item remote_refs ( REPOSITORY [, GROUPS [, REFGLOBS ] ] )
+
+This function returns a hashref of refs stored in a given remote repository.
+The hash is in the format C<refname =\> hash>. For tags, the C<refname> entry
+contains the tag object while a C<refname^{}> entry gives the tagged objects.
+
+C<REPOSITORY> has the same meaning as the appropriate C<git-ls-remote>
+argument; either a URL or a remote name (if called on a repository instance).
+C<GROUPS> is an optional arrayref that can contain 'tags' to return all the
+tags and/or 'heads' to return all the heads. C<REFGLOB> is an optional array
+of strings containing a shell-like glob to further limit the refs returned in
+the hash; the meaning is again the same as the appropriate C<git-ls-remote>
+argument.
+
+This function may or may not be called on a repository instance. In the former
+case, remote names as defined in the repository are recognized as repository
+specifiers.
+
+=cut
+
+sub remote_refs {
+	my ($self, $repo, $groups, $refglobs) = _maybe_self(@_);
+	my @args;
+	if (ref $groups eq 'ARRAY') {
+		foreach (@$groups) {
+			if ($_ eq 'heads') {
+				push (@args, '--heads');
+			} elsif ($_ eq 'tags') {
+				push (@args, '--tags');
+			} else {
+				# Ignore unknown groups for future
+				# compatibility
+			}
+		}
+	}
+	push (@args, $repo);
+	if (ref $refglobs eq 'ARRAY') {
+		push (@args, @$refglobs);
+	}
+
+	my @self = $self ? ($self) : (); # Ultra trickery
+	my ($fh, $ctx) = Git::command_output_pipe(@self, 'ls-remote', @args);
+	my %refs;
+	while (<$fh>) {
+		chomp;
+		my ($hash, $ref) = split(/\t/, $_, 2);
+		$refs{$ref} = $hash;
+	}
+	Git::command_close_pipe(@self, $fh, $ctx);
+	return \%refs;
+}
+
+
+=item ident ( TYPE | IDENTSTR )
+
+=item ident_person ( TYPE | IDENTSTR | IDENTARRAY )
+
+This suite of functions retrieves and parses ident information, as stored
+in the commit and tag objects or produced by C<var GIT_type_IDENT> (thus
+C<TYPE> can be either I<author> or I<committer>; case is insignificant).
+
+The C<ident> method retrieves the ident information from C<git var>
+and either returns it as a scalar string or as an array with the fields parsed.
+Alternatively, it can take a prepared ident string (e.g. from the commit
+object) and just parse it.
+
+C<ident_person> returns the person part of the ident - name and email;
+it can take the same arguments as C<ident> or the array returned by C<ident>.
+
+The synopsis is like:
+
+	my ($name, $email, $time_tz) = ident('author');
+	"$name <$email>" eq ident_person('author');
+	"$name <$email>" eq ident_person($name);
+	$time_tz =~ /^\d+ [+-]\d{4}$/;
+
+=cut
+
+sub ident {
+	my ($self, $type) = _maybe_self(@_);
+	my $identstr;
+	if (lc $type eq lc 'committer' or lc $type eq lc 'author') {
+		my @cmd = ('var', 'GIT_'.uc($type).'_IDENT');
+		unshift @cmd, $self if $self;
+		$identstr = command_oneline(@cmd);
+	} else {
+		$identstr = $type;
+	}
+	if (wantarray) {
+		return $identstr =~ /^(.*) <(.*)> (\d+ [+-]\d{4})$/;
+	} else {
+		return $identstr;
+	}
+}
+
+sub ident_person {
+	my ($self, @ident) = _maybe_self(@_);
+	$#ident == 0 and @ident = $self ? $self->ident($ident[0]) : ident($ident[0]);
+	return "$ident[0] <$ident[1]>";
+}
+
+=item hash_object ( TYPE, FILENAME )
+
+Compute the SHA1 object id of the given C<FILENAME> considering it is
+of the C<TYPE> object type (C<blob>, C<commit>, C<tree>).
+
+The method can be called without any instance or on a specified Git repository,
+it makes zero difference.
+
+The function returns the SHA1 hash.
+
+=cut
+
+# TODO: Support for passing FILEHANDLE instead of FILENAME
+sub hash_object {
+	my ($self, $type, $file) = _maybe_self(@_);
+	command_oneline('hash-object', '-t', $type, $file);
+}
+
+
+=item hash_and_insert_object ( FILENAME )
+
+Compute the SHA1 object id of the given C<FILENAME> and add the object to the
+object database.
+
+The function returns the SHA1 hash.
+
+=cut
+
+# TODO: Support for passing FILEHANDLE instead of FILENAME
+sub hash_and_insert_object {
+	my ($self, $filename) = @_;
+
+	carp "Bad filename \"$filename\"" if $filename =~ /[\r\n]/;
+
+	$self->_open_hash_and_insert_object_if_needed();
+	my ($in, $out) = ($self->{hash_object_in}, $self->{hash_object_out});
+
+	unless (print $out $filename, "\n") {
+		$self->_close_hash_and_insert_object();
+		throw Error::Simple("out pipe went bad");
+	}
+
+	chomp(my $hash = <$in>);
+	unless (defined($hash)) {
+		$self->_close_hash_and_insert_object();
+		throw Error::Simple("in pipe went bad");
+	}
+
+	return $hash;
+}
+
+sub _open_hash_and_insert_object_if_needed {
+	my ($self) = @_;
+
+	return if defined($self->{hash_object_pid});
+
+	($self->{hash_object_pid}, $self->{hash_object_in},
+	 $self->{hash_object_out}, $self->{hash_object_ctx}) =
+		$self->command_bidi_pipe(qw(hash-object -w --stdin-paths --no-filters));
+}
+
+sub _close_hash_and_insert_object {
+	my ($self) = @_;
+
+	return unless defined($self->{hash_object_pid});
+
+	my @vars = map { 'hash_object_' . $_ } qw(pid in out ctx);
+
+	command_close_bidi_pipe(@$self{@vars});
+	delete @$self{@vars};
+}
+
+=item cat_blob ( SHA1, FILEHANDLE )
+
+Prints the contents of the blob identified by C<SHA1> to C<FILEHANDLE> and
+returns the number of bytes printed.
+
+=cut
+
+sub cat_blob {
+	my ($self, $sha1, $fh) = @_;
+
+	$self->_open_cat_blob_if_needed();
+	my ($in, $out) = ($self->{cat_blob_in}, $self->{cat_blob_out});
+
+	unless (print $out $sha1, "\n") {
+		$self->_close_cat_blob();
+		throw Error::Simple("out pipe went bad");
+	}
+
+	my $description = <$in>;
+	if ($description =~ / missing$/) {
+		carp "$sha1 doesn't exist in the repository";
+		return -1;
+	}
+
+	if ($description !~ /^[0-9a-fA-F]{40}(?:[0-9a-fA-F]{24})? \S+ (\d+)$/) {
+		carp "Unexpected result returned from git cat-file";
+		return -1;
+	}
+
+	my $size = $1;
+
+	my $blob;
+	my $bytesLeft = $size;
+
+	while (1) {
+		last unless $bytesLeft;
+
+		my $bytesToRead = $bytesLeft < 1024 ? $bytesLeft : 1024;
+		my $read = read($in, $blob, $bytesToRead);
+		unless (defined($read)) {
+			$self->_close_cat_blob();
+			throw Error::Simple("in pipe went bad");
+		}
+		unless (print $fh $blob) {
+			$self->_close_cat_blob();
+			throw Error::Simple("couldn't write to passed in filehandle");
+		}
+		$bytesLeft -= $read;
+	}
+
+	# Skip past the trailing newline.
+	my $newline;
+	my $read = read($in, $newline, 1);
+	unless (defined($read)) {
+		$self->_close_cat_blob();
+		throw Error::Simple("in pipe went bad");
+	}
+	unless ($read == 1 && $newline eq "\n") {
+		$self->_close_cat_blob();
+		throw Error::Simple("didn't find newline after blob");
+	}
+
+	return $size;
+}
+
+sub _open_cat_blob_if_needed {
+	my ($self) = @_;
+
+	return if defined($self->{cat_blob_pid});
+
+	($self->{cat_blob_pid}, $self->{cat_blob_in},
+	 $self->{cat_blob_out}, $self->{cat_blob_ctx}) =
+		$self->command_bidi_pipe(qw(cat-file --batch));
+}
+
+sub _close_cat_blob {
+	my ($self) = @_;
+
+	return unless defined($self->{cat_blob_pid});
+
+	my @vars = map { 'cat_blob_' . $_ } qw(pid in out ctx);
+
+	command_close_bidi_pipe(@$self{@vars});
+	delete @$self{@vars};
+}
+
+
+=item credential_read( FILEHANDLE )
+
+Reads credential key-value pairs from C<FILEHANDLE>.  Reading stops at EOF or
+when an empty line is encountered.  Each line must be of the form C<key=value>
+with a non-empty key.  Function returns hash with all read values.  Any white
+space (other than new-line character) is preserved.
+
+=cut
+
+sub credential_read {
+	my ($self, $reader) = _maybe_self(@_);
+	my %credential;
+	while (<$reader>) {
+		chomp;
+		if ($_ eq '') {
+			last;
+		} elsif (!/^([^=]+)=(.*)$/) {
+			throw Error::Simple("unable to parse git credential data:\n$_");
+		}
+		$credential{$1} = $2;
+	}
+	return %credential;
+}
+
+=item credential_write( FILEHANDLE, CREDENTIAL_HASHREF )
+
+Writes credential key-value pairs from hash referenced by
+C<CREDENTIAL_HASHREF> to C<FILEHANDLE>.  Keys and values cannot contain
+new-lines or NUL bytes characters, and key cannot contain equal signs nor be
+empty (if they do Error::Simple is thrown).  Any white space is preserved.  If
+value for a key is C<undef>, it will be skipped.
+
+If C<'url'> key exists it will be written first.  (All the other key-value
+pairs are written in sorted order but you should not depend on that).  Once
+all lines are written, an empty line is printed.
+
+=cut
+
+sub credential_write {
+	my ($self, $writer, $credential) = _maybe_self(@_);
+	my ($key, $value);
+
+	# Check if $credential is valid prior to writing anything
+	while (($key, $value) = each %$credential) {
+		if (!defined $key || !length $key) {
+			throw Error::Simple("credential key empty or undefined");
+		} elsif ($key =~ /[=\n\0]/) {
+			throw Error::Simple("credential key contains invalid characters: $key");
+		} elsif (defined $value && $value =~ /[\n\0]/) {
+			throw Error::Simple("credential value for key=$key contains invalid characters: $value");
+		}
+	}
+
+	for $key (sort {
+		# url overwrites other fields, so it must come first
+		return -1 if $a eq 'url';
+		return  1 if $b eq 'url';
+		return $a cmp $b;
+	} keys %$credential) {
+		if (defined $credential->{$key}) {
+			print $writer $key, '=', $credential->{$key}, "\n";
+		}
+	}
+	print $writer "\n";
+}
+
+sub _credential_run {
+	my ($self, $credential, $op) = _maybe_self(@_);
+	my ($pid, $reader, $writer, $ctx) = command_bidi_pipe('credential', $op);
+
+	credential_write $writer, $credential;
+	close $writer;
+
+	if ($op eq "fill") {
+		%$credential = credential_read $reader;
+	}
+	if (<$reader>) {
+		throw Error::Simple("unexpected output from git credential $op response:\n$_\n");
+	}
+
+	command_close_bidi_pipe($pid, $reader, undef, $ctx);
+}
+
+=item credential( CREDENTIAL_HASHREF [, OPERATION ] )
+
+=item credential( CREDENTIAL_HASHREF, CODE )
+
+Executes C<git credential> for a given set of credentials and specified
+operation.  In both forms C<CREDENTIAL_HASHREF> needs to be a reference to
+a hash which stores credentials.  Under certain conditions the hash can
+change.
+
+In the first form, C<OPERATION> can be C<'fill'>, C<'approve'> or C<'reject'>,
+and function will execute corresponding C<git credential> sub-command.  If
+it's omitted C<'fill'> is assumed.  In case of C<'fill'> the values stored in
+C<CREDENTIAL_HASHREF> will be changed to the ones returned by the C<git
+credential fill> command.  The usual usage would look something like:
+
+	my %cred = (
+		'protocol' => 'https',
+		'host' => 'example.com',
+		'username' => 'bob'
+	);
+	Git::credential \%cred;
+	if (try_to_authenticate($cred{'username'}, $cred{'password'})) {
+		Git::credential \%cred, 'approve';
+		... do more stuff ...
+	} else {
+		Git::credential \%cred, 'reject';
+	}
+
+In the second form, C<CODE> needs to be a reference to a subroutine.  The
+function will execute C<git credential fill> to fill the provided credential
+hash, then call C<CODE> with C<CREDENTIAL_HASHREF> as the sole argument.  If
+C<CODE>'s return value is defined, the function will execute C<git credential
+approve> (if return value yields true) or C<git credential reject> (if return
+value is false).  If the return value is undef, nothing at all is executed;
+this is useful, for example, if the credential could neither be verified nor
+rejected due to an unrelated network error.  The return value is the same as
+what C<CODE> returns.  With this form, the usage might look as follows:
+
+	if (Git::credential {
+		'protocol' => 'https',
+		'host' => 'example.com',
+		'username' => 'bob'
+	}, sub {
+		my $cred = shift;
+		return !!try_to_authenticate($cred->{'username'},
+		                             $cred->{'password'});
+	}) {
+		... do more stuff ...
+	}
+
+=cut
+
+sub credential {
+	my ($self, $credential, $op_or_code) = (_maybe_self(@_), 'fill');
+
+	if ('CODE' eq ref $op_or_code) {
+		_credential_run $credential, 'fill';
+		my $ret = $op_or_code->($credential);
+		if (defined $ret) {
+			_credential_run $credential, $ret ? 'approve' : 'reject';
+		}
+		return $ret;
+	} else {
+		_credential_run $credential, $op_or_code;
+	}
+}
+
+{ # %TEMP_* Lexical Context
+
+my (%TEMP_FILEMAP, %TEMP_FILES);
+
+=item temp_acquire ( NAME )
+
+Attempts to retrieve the temporary file mapped to the string C<NAME>. If an
+associated temp file has not been created this session or was closed, it is
+created, cached, and set for autoflush and binmode.
+
+Internally locks the file mapped to C<NAME>. This lock must be released with
+C<temp_release()> when the temp file is no longer needed. Subsequent attempts
+to retrieve temporary files mapped to the same C<NAME> while still locked will
+cause an error. This locking mechanism provides a weak guarantee and is not
+threadsafe. It does provide some error checking to help prevent temp file refs
+writing over one another.
+
+In general, the L<File::Handle> returned should not be closed by consumers as
+it defeats the purpose of this caching mechanism. If you need to close the temp
+file handle, then you should use L<File::Temp> or another temp file faculty
+directly. If a handle is closed and then requested again, then a warning will
+issue.
+
+=cut
+
+sub temp_acquire {
+	my $temp_fd = _temp_cache(@_);
+
+	$TEMP_FILES{$temp_fd}{locked} = 1;
+	$temp_fd;
+}
+
+=item temp_is_locked ( NAME )
+
+Returns true if the internal lock created by a previous C<temp_acquire()>
+call with C<NAME> is still in effect.
+
+When temp_acquire is called on a C<NAME>, it internally locks the temporary
+file mapped to C<NAME>.  That lock will not be released until C<temp_release()>
+is called with either the original C<NAME> or the L<File::Handle> that was
+returned from the original call to temp_acquire.
+
+Subsequent attempts to call C<temp_acquire()> with the same C<NAME> will fail
+unless there has been an intervening C<temp_release()> call for that C<NAME>
+(or its corresponding L<File::Handle> that was returned by the original
+C<temp_acquire()> call).
+
+If true is returned by C<temp_is_locked()> for a C<NAME>, an attempt to
+C<temp_acquire()> the same C<NAME> will cause an error unless
+C<temp_release> is first called on that C<NAME> (or its corresponding
+L<File::Handle> that was returned by the original C<temp_acquire()> call).
+
+=cut
+
+sub temp_is_locked {
+	my ($self, $name) = _maybe_self(@_);
+	my $temp_fd = \$TEMP_FILEMAP{$name};
+
+	defined $$temp_fd && $$temp_fd->opened && $TEMP_FILES{$$temp_fd}{locked};
+}
+
+=item temp_release ( NAME )
+
+=item temp_release ( FILEHANDLE )
+
+Releases a lock acquired through C<temp_acquire()>. Can be called either with
+the C<NAME> mapping used when acquiring the temp file or with the C<FILEHANDLE>
+referencing a locked temp file.
+
+Warns if an attempt is made to release a file that is not locked.
+
+The temp file will be truncated before being released. This can help to reduce
+disk I/O where the system is smart enough to detect the truncation while data
+is in the output buffers. Beware that after the temp file is released and
+truncated, any operations on that file may fail miserably until it is
+re-acquired. All contents are lost between each release and acquire mapped to
+the same string.
+
+=cut
+
+sub temp_release {
+	my ($self, $temp_fd, $trunc) = _maybe_self(@_);
+
+	if (exists $TEMP_FILEMAP{$temp_fd}) {
+		$temp_fd = $TEMP_FILES{$temp_fd};
+	}
+	unless ($TEMP_FILES{$temp_fd}{locked}) {
+		carp "Attempt to release temp file '",
+			$temp_fd, "' that has not been locked";
+	}
+	temp_reset($temp_fd) if $trunc and $temp_fd->opened;
+
+	$TEMP_FILES{$temp_fd}{locked} = 0;
+	undef;
+}
+
+sub _temp_cache {
+	my ($self, $name) = _maybe_self(@_);
+
+	my $temp_fd = \$TEMP_FILEMAP{$name};
+	if (defined $$temp_fd and $$temp_fd->opened) {
+		if ($TEMP_FILES{$$temp_fd}{locked}) {
+			throw Error::Simple("Temp file with moniker '" .
+				$name . "' already in use");
+		}
+	} else {
+		if (defined $$temp_fd) {
+			# then we're here because of a closed handle.
+			carp "Temp file '", $name,
+				"' was closed. Opening replacement.";
+		}
+		my $fname;
+
+		my $tmpdir;
+		if (defined $self) {
+			$tmpdir = $self->repo_path();
+		}
+
+		my $n = $name;
+		$n =~ s/\W/_/g; # no strange chars
+
+		($$temp_fd, $fname) = File::Temp::tempfile(
+			"Git_${n}_XXXXXX", UNLINK => 1, DIR => $tmpdir,
+			) or throw Error::Simple("couldn't open new temp file");
+
+		$$temp_fd->autoflush;
+		binmode $$temp_fd;
+		$TEMP_FILES{$$temp_fd}{fname} = $fname;
+	}
+	$$temp_fd;
+}
+
+=item temp_reset ( FILEHANDLE )
+
+Truncates and resets the position of the C<FILEHANDLE>.
+
+=cut
+
+sub temp_reset {
+	my ($self, $temp_fd) = _maybe_self(@_);
+
+	truncate $temp_fd, 0
+		or throw Error::Simple("couldn't truncate file");
+	sysseek($temp_fd, 0, SEEK_SET) and seek($temp_fd, 0, SEEK_SET)
+		or throw Error::Simple("couldn't seek to beginning of file");
+	sysseek($temp_fd, 0, SEEK_CUR) == 0 and tell($temp_fd) == 0
+		or throw Error::Simple("expected file position to be reset");
+}
+
+=item temp_path ( NAME )
+
+=item temp_path ( FILEHANDLE )
+
+Returns the filename associated with the given tempfile.
+
+=cut
+
+sub temp_path {
+	my ($self, $temp_fd) = _maybe_self(@_);
+
+	if (exists $TEMP_FILEMAP{$temp_fd}) {
+		$temp_fd = $TEMP_FILEMAP{$temp_fd};
+	}
+	$TEMP_FILES{$temp_fd}{fname};
+}
+
+sub END {
+	unlink values %TEMP_FILEMAP if %TEMP_FILEMAP;
+}
+
+} # %TEMP_* Lexical Context
+
+=item prefix_lines ( PREFIX, STRING [, STRING... ])
+
+Prefixes lines in C<STRING> with C<PREFIX>.
+
+=cut
+
+sub prefix_lines {
+	my $prefix = shift;
+	my $string = join("\n", @_);
+	$string =~ s/^/$prefix/mg;
+	return $string;
+}
+
+=item unquote_path ( PATH )
+
+Unquote a quoted path containing c-escapes as returned by ls-files etc.
+when not using -z or when parsing the output of diff -u.
+
+=cut
+
+{
+	my %cquote_map = (
+		"a" => chr(7),
+		"b" => chr(8),
+		"t" => chr(9),
+		"n" => chr(10),
+		"v" => chr(11),
+		"f" => chr(12),
+		"r" => chr(13),
+		"\\" => "\\",
+		"\042" => "\042",
+	);
+
+	sub unquote_path {
+		local ($_) = @_;
+		my ($retval, $remainder);
+		if (!/^\042(.*)\042$/) {
+			return $_;
+		}
+		($_, $retval) = ($1, "");
+		while (/^([^\\]*)\\(.*)$/) {
+			$remainder = $2;
+			$retval .= $1;
+			for ($remainder) {
+				if (/^([0-3][0-7][0-7])(.*)$/) {
+					$retval .= chr(oct($1));
+					$_ = $2;
+					last;
+				}
+				if (/^([\\\042abtnvfr])(.*)$/) {
+					$retval .= $cquote_map{$1};
+					$_ = $2;
+					last;
+				}
+				# This is malformed
+				throw Error::Simple("invalid quoted path $_[0]");
+			}
+			$_ = $remainder;
+		}
+		$retval .= $_;
+		return $retval;
+	}
+}
+
+=item get_comment_line_char ( )
+
+Gets the core.commentchar configuration value.
+The value falls-back to '#' if core.commentchar is set to 'auto'.
+
+=cut
+
+sub get_comment_line_char {
+	my $comment_line_char = config("core.commentchar") || '#';
+	$comment_line_char = '#' if ($comment_line_char eq 'auto');
+	$comment_line_char = '#' if (length($comment_line_char) != 1);
+	return $comment_line_char;
+}
+
+=item comment_lines ( STRING [, STRING... ])
+
+Comments lines following core.commentchar configuration.
+
+=cut
+
+sub comment_lines {
+	my $comment_line_char = get_comment_line_char;
+	return prefix_lines("$comment_line_char ", @_);
+}
+
+=back
+
+=head1 ERROR HANDLING
+
+All functions are supposed to throw Perl exceptions in case of errors.
+See the L<Error> module on how to catch those. Most exceptions are mere
+L<Error::Simple> instances.
+
+However, the C<command()>, C<command_oneline()> and C<command_noisy()>
+functions suite can throw C<Git::Error::Command> exceptions as well: those are
+thrown when the external command returns an error code and contain the error
+code as well as access to the captured command's output. The exception class
+provides the usual C<stringify> and C<value> (command's exit code) methods and
+in addition also a C<cmd_output> method that returns either an array or a
+string with the captured command output (depending on the original function
+call context; C<command_noisy()> returns C<undef>) and $<cmdline> which
+returns the command and its arguments (but without proper quoting).
+
+Note that the C<command_*_pipe()> functions cannot throw this exception since
+it has no idea whether the command failed or not. You will only find out
+at the time you C<close> the pipe; if you want to have that automated,
+use C<command_close_pipe()>, which can throw the exception.
+
+=cut
+
+{
+	package Git::Error::Command;
+
+	@Git::Error::Command::ISA = qw(Error);
+
+	sub new {
+		my $self = shift;
+		my $cmdline = '' . shift;
+		my $value = 0 + shift;
+		my $outputref = shift;
+		my(@args) = ();
+
+		local $Error::Depth = $Error::Depth + 1;
+
+		push(@args, '-cmdline', $cmdline);
+		push(@args, '-value', $value);
+		push(@args, '-outputref', $outputref);
+
+		$self->SUPER::new(-text => 'command returned error', @args);
+	}
+
+	sub stringify {
+		my $self = shift;
+		my $text = $self->SUPER::stringify;
+		$self->cmdline() . ': ' . $text . ': ' . $self->value() . "\n";
+	}
+
+	sub cmdline {
+		my $self = shift;
+		$self->{'-cmdline'};
+	}
+
+	sub cmd_output {
+		my $self = shift;
+		my $ref = $self->{'-outputref'};
+		defined $ref or undef;
+		if (ref $ref eq 'ARRAY') {
+			return @$ref;
+		} else { # SCALAR
+			return $$ref;
+		}
+	}
+}
+
+=over 4
+
+=item git_cmd_try { CODE } ERRMSG
+
+This magical statement will automatically catch any C<Git::Error::Command>
+exceptions thrown by C<CODE> and make your program die with C<ERRMSG>
+on its lips; the message will have %s substituted for the command line
+and %d for the exit status. This statement is useful mostly for producing
+more user-friendly error messages.
+
+In case of no exception caught the statement returns C<CODE>'s return value.
+
+Note that this is the only auto-exported function.
+
+=cut
+
+sub git_cmd_try(&$) {
+	my ($code, $errmsg) = @_;
+	my @result;
+	my $err;
+	my $array = wantarray;
+	try {
+		if ($array) {
+			@result = &$code;
+		} else {
+			$result[0] = &$code;
+		}
+	} catch Git::Error::Command with {
+		my $E = shift;
+		$err = $errmsg;
+		$err =~ s/\%s/$E->cmdline()/ge;
+		$err =~ s/\%d/$E->value()/ge;
+		# We can't croak here since Error.pm would mangle
+		# that to Error::Simple.
+	};
+	$err and croak $err;
+	return $array ? @result : $result[0];
+}
+
+
+=back
+
+=head1 COPYRIGHT
+
+Copyright 2006 by Petr Baudis E<lt>pasky@suse.czE<gt>.
+
+This module is free software; it may be used, copied, modified
+and distributed under the terms of the GNU General Public Licence,
+either version 2, or (at your option) any later version.
+
+=cut
+
+
+# Take raw method argument list and return ($obj, @args) in case
+# the method was called upon an instance and (undef, @args) if
+# it was called directly.
+sub _maybe_self {
+	UNIVERSAL::isa($_[0], 'Git') ? @_ : (undef, @_);
+}
+
+# Check if the command id is something reasonable.
+sub _check_valid_cmd {
+	my ($cmd) = @_;
+	$cmd =~ /^[a-z0-9A-Z_-]+$/ or throw Error::Simple("bad command: $cmd");
+}
+
+# Common backend for the pipe creators.
+sub _command_common_pipe {
+	my $direction = shift;
+	my ($self, @p) = _maybe_self(@_);
+	my (%opts, $cmd, @args);
+	if (ref $p[0]) {
+		($cmd, @args) = @{shift @p};
+		%opts = ref $p[0] ? %{$p[0]} : @p;
+	} else {
+		($cmd, @args) = @p;
+	}
+	_check_valid_cmd($cmd);
+
+	my $fh;
+	if ($^O eq 'MSWin32') {
+		# ActiveState Perl
+		#defined $opts{STDERR} and
+		#	warn 'ignoring STDERR option - running w/ ActiveState';
+		$direction eq '-|' or
+			die 'input pipe for ActiveState not implemented';
+		# the strange construction with *ACPIPE is just to
+		# explain the tie below that we want to bind to
+		# a handle class, not scalar. It is not known if
+		# it is something specific to ActiveState Perl or
+		# just a Perl quirk.
+		tie (*ACPIPE, 'Git::activestate_pipe', $cmd, @args);
+		$fh = *ACPIPE;
+
+	} else {
+		my $pid = open($fh, $direction);
+		if (not defined $pid) {
+			throw Error::Simple("open failed: $!");
+		} elsif ($pid == 0) {
+			if ($opts{STDERR}) {
+				open (STDERR, '>&', $opts{STDERR})
+					or die "dup failed: $!";
+			} elsif (defined $opts{STDERR}) {
+				open (STDERR, '>', '/dev/null')
+					or die "opening /dev/null failed: $!";
+			}
+			_cmd_exec($self, $cmd, @args);
+		}
+	}
+	return wantarray ? ($fh, join(' ', $cmd, @args)) : $fh;
+}
+
+# When already in the subprocess, set up the appropriate state
+# for the given repository and execute the git command.
+sub _cmd_exec {
+	my ($self, @args) = @_;
+	_setup_git_cmd_env($self);
+	_execv_git_cmd(@args);
+	die qq[exec "@args" failed: $!];
+}
+
+# set up the appropriate state for git command
+sub _setup_git_cmd_env {
+	my $self = shift;
+	if ($self) {
+		$self->repo_path() and $ENV{'GIT_DIR'} = $self->repo_path();
+		$self->repo_path() and $self->wc_path()
+			and $ENV{'GIT_WORK_TREE'} = $self->wc_path();
+		$self->wc_path() and chdir($self->wc_path());
+		$self->wc_subdir() and chdir($self->wc_subdir());
+	}
+}
+
+# Execute the given Git command ($_[0]) with arguments ($_[1..])
+# by searching for it at proper places.
+sub _execv_git_cmd { exec('git', @_); }
+
+# Close pipe to a subprocess.
+sub _cmd_close {
+	my $ctx = shift @_;
+	foreach my $fh (@_) {
+		if (close $fh) {
+			# nop
+		} elsif ($!) {
+			# It's just close, no point in fatalities
+			carp "error closing pipe: $!";
+		} elsif ($? >> 8) {
+			# The caller should pepper this.
+			throw Git::Error::Command($ctx, $? >> 8);
+		}
+		# else we might e.g. closed a live stream; the command
+		# dying of SIGPIPE would drive us here.
+	}
+}
+
+
+sub DESTROY {
+	my ($self) = @_;
+	$self->_close_hash_and_insert_object();
+	$self->_close_cat_blob();
+}
+
+
+# Pipe implementation for ActiveState Perl.
+
+package Git::activestate_pipe;
+
+sub TIEHANDLE {
+	my ($class, @params) = @_;
+	# FIXME: This is probably horrible idea and the thing will explode
+	# at the moment you give it arguments that require some quoting,
+	# but I have no ActiveState clue... --pasky
+	# Let's just hope ActiveState Perl does at least the quoting
+	# correctly.
+	my @data = qx{git @params};
+	bless { i => 0, data => \@data }, $class;
+}
+
+sub READLINE {
+	my $self = shift;
+	if ($self->{i} >= scalar @{$self->{data}}) {
+		return undef;
+	}
+	my $i = $self->{i};
+	if (wantarray) {
+		$self->{i} = $#{$self->{'data'}} + 1;
+		return splice(@{$self->{'data'}}, $i);
+	}
+	$self->{i} = $i + 1;
+	return $self->{'data'}->[ $i ];
+}
+
+sub CLOSE {
+	my $self = shift;
+	delete $self->{data};
+	delete $self->{i};
+}
+
+sub EOF {
+	my $self = shift;
+	return ($self->{i} >= scalar @{$self->{data}});
+}
+
+
+1; # Famous last words