git-difftool.perl - jrn/git - Git at Google

 #!/usr/bin/perl
 # Copyright (c) 2009, 2010 David Aguilar
 # Copyright (c) 2012 Tim Henigan
 #
 # This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
 # git-difftool--helper script.
 #
 # This script exports GIT_EXTERNAL_DIFF and GIT_PAGER for use by git.
 # The GIT_DIFF* variables are exported for use by git-difftool--helper.
 #
 # Any arguments that are unknown to this script are forwarded to 'git diff'.

 use 5.008;
 use strict;
 use warnings;
 use File::Basename qw(dirname);
 use File::Copy;
 use File::Compare;
 use File::Find;
 use File::stat;
 use File::Path qw(mkpath);
 use File::Temp qw(tempdir);
 use Getopt::Long qw(:config pass_through);
 use Git;

 my @tools;
 my @working_tree;
 my $rc;
 my $repo = Git->repository();
 my $repo_path = $repo->repo_path();

 sub usage
 {
 	my $exitcode = shift;
 	print << 'USAGE';
 usage: git difftool [-t|--tool=<tool>] [--tool-help]
                     [-x|--extcmd=<cmd>]
                     [-g|--gui] [--no-gui]
                     [--prompt] [-y|--no-prompt]
                     [-d|--dir-diff]
                     ['git diff' options]
 USAGE
 	exit($exitcode);
 }

 sub find_worktree
 {
 	# Git->repository->wc_path() does not honor changes to the working
 	# tree location made by $ENV{GIT_WORK_TREE} or the 'core.worktree'
 	# config variable.
 	my $worktree;
 	my $env_worktree = $ENV{GIT_WORK_TREE};
 	my $core_worktree = Git::config('core.worktree');

 	if (defined($env_worktree) and (length($env_worktree) > 0)) {
 		$worktree = $env_worktree;
 	} elsif (defined($core_worktree) and (length($core_worktree) > 0)) {
 		$worktree = $core_worktree;
 	} else {
 		$worktree = $repo->wc_path();
 	}

 	return $worktree;
 }

 my $workdir = find_worktree();

 sub filter_tool_scripts
 {
 	if (-d $_) {
 		if ($_ ne ".") {
 			# Ignore files in subdirectories
 			$File::Find::prune = 1;
 		}
 	} else {
 		if ((-f $_) && ($_ ne "defaults")) {
 			push(@tools, $_);
 		}
 	}
 }

 sub print_tool_help
 {
 	my ($cmd, @found, @notfound);
 	my $gitpath = Git::exec_path();

 	find(\&filter_tool_scripts, "$gitpath/mergetools");

 	foreach my $tool (@tools) {
 		$cmd  = "TOOL_MODE=diff";
 		$cmd .= ' && . "$(git --exec-path)/git-mergetool--lib"';
 		$cmd .= " && get_merge_tool_path $tool >/dev/null 2>&1";
 		$cmd .= " && can_diff >/dev/null 2>&1";
 		if (system('sh', '-c', $cmd) == 0) {
 			push(@found, $tool);
 		} else {
 			push(@notfound, $tool);
 		}
 	}

 	print "'git difftool --tool=<tool>' may be set to one of the following:\n";
 	print "\t$_\n" for (sort(@found));

 	print "\nThe following tools are valid, but not currently available:\n";
 	print "\t$_\n" for (sort(@notfound));

 	print "\nNOTE: Some of the tools listed above only work in a windowed\n";
 	print "environment. If run in a terminal-only session, they will fail.\n";

 	exit(0);
 }

 sub setup_dir_diff
 {
 	# Run the diff; exit immediately if no diff found
 	# 'Repository' and 'WorkingCopy' must be explicitly set to insure that
 	# if $GIT_DIR and $GIT_WORK_TREE are set in ENV, they are actually used
 	# by Git->repository->command*.
 	my $diffrepo = Git->repository(Repository => $repo_path, WorkingCopy => $workdir);
 	my $diffrtn = $diffrepo->command_oneline('diff', '--raw', '--no-abbrev', '-z', @ARGV);
 	exit(0) if (length($diffrtn) == 0);

 	# Setup temp directories
 	my $tmpdir = tempdir('git-diffall.XXXXX', CLEANUP => 1, TMPDIR => 1);
 	my $ldir = "$tmpdir/left";
 	my $rdir = "$tmpdir/right";
 	mkpath($ldir) or die $!;
 	mkpath($rdir) or die $!;

 	# Build index info for left and right sides of the diff
 	my $submodule_mode = '160000';
 	my $symlink_mode = '120000';
 	my $null_mode = '0' x 6;
 	my $null_sha1 = '0' x 40;
 	my $lindex = '';
 	my $rindex = '';
 	my %submodule;
 	my %symlink;
 	my @rawdiff = split('\0', $diffrtn);

 	my $i = 0;
 	while ($i < $#rawdiff) {
 		if ($rawdiff[$i] =~ /^::/) {
 			print "Combined diff formats ('-c' and '--cc') are not supported in directory diff mode.\n";
 			exit(1);
 		}

 		my ($lmode, $rmode, $lsha1, $rsha1, $status) = split(' ', substr($rawdiff[$i], 1));
 		my $src_path = $rawdiff[$i + 1];
 		my $dst_path;

 		if ($status =~ /^[CR]/) {
 			$dst_path = $rawdiff[$i + 2];
 			$i += 3;
 		} else {
 			$dst_path = $src_path;
 			$i += 2;
 		}

 		if (($lmode eq $submodule_mode) or ($rmode eq $submodule_mode)) {
 			$submodule{$src_path}{left} = $lsha1;
 			if ($lsha1 ne $rsha1) {
 				$submodule{$dst_path}{right} = $rsha1;
 			} else {
 				$submodule{$dst_path}{right} = "$rsha1-dirty";
 			}
 			next;
 		}

 		if ($lmode eq $symlink_mode) {
 			$symlink{$src_path}{left} = $diffrepo->command_oneline('show', "$lsha1");
 		}

 		if ($rmode eq $symlink_mode) {
 			$symlink{$dst_path}{right} = $diffrepo->command_oneline('show', "$rsha1");
 		}

 		if (($lmode ne $null_mode) and ($status !~ /^C/)) {
 			$lindex .= "$lmode $lsha1\t$src_path\0";
 		}

 		if ($rmode ne $null_mode) {
 			if ($rsha1 ne $null_sha1) {
 				$rindex .= "$rmode $rsha1\t$dst_path\0";
 			} else {
 				push(@working_tree, $dst_path);
 			}
 		}
 	}

 	# If $GIT_DIR is not set prior to calling 'git update-index' and
 	# 'git checkout-index', then those commands will fail if difftool
 	# is called from a directory other than the repo root.
 	my $must_unset_git_dir = 0;
 	if (not defined($ENV{GIT_DIR})) {
 		$must_unset_git_dir = 1;
 		$ENV{GIT_DIR} = $repo_path;
 	}

 	# Populate the left and right directories based on each index file
 	my ($inpipe, $ctx);
 	$ENV{GIT_INDEX_FILE} = "$tmpdir/lindex";
 	($inpipe, $ctx) = $repo->command_input_pipe(qw/update-index -z --index-info/);
 	print($inpipe $lindex);
 	$repo->command_close_pipe($inpipe, $ctx);
 	$rc = system('git', 'checkout-index', '--all', "--prefix=$ldir/");
 	exit($rc | ($rc >> 8)) if ($rc != 0);

 	$ENV{GIT_INDEX_FILE} = "$tmpdir/rindex";
 	($inpipe, $ctx) = $repo->command_input_pipe(qw/update-index -z --index-info/);
 	print($inpipe $rindex);
 	$repo->command_close_pipe($inpipe, $ctx);
 	$rc = system('git', 'checkout-index', '--all', "--prefix=$rdir/");
 	exit($rc | ($rc >> 8)) if ($rc != 0);

 	# If $GIT_DIR was explicitly set just for the update/checkout
 	# commands, then it should be unset before continuing.
 	delete($ENV{GIT_DIR}) if ($must_unset_git_dir);
 	delete($ENV{GIT_INDEX_FILE});

 	# Changes in the working tree need special treatment since they are
 	# not part of the index
 	for my $file (@working_tree) {
 		my $dir = dirname($file);
 		unless (-d "$rdir/$dir") {
 			mkpath("$rdir/$dir") or die $!;
 		}
 		copy("$workdir/$file", "$rdir/$file") or die $!;
 		chmod(stat("$workdir/$file")->mode, "$rdir/$file") or die $!;
 	}

 	# Changes to submodules require special treatment. This loop writes a
 	# temporary file to both the left and right directories to show the
 	# change in the recorded SHA1 for the submodule.
 	for my $path (keys %submodule) {
 		if (defined($submodule{$path}{left})) {
 			write_to_file("$ldir/$path", "Subproject commit $submodule{$path}{left}");
 		}
 		if (defined($submodule{$path}{right})) {
 			write_to_file("$rdir/$path", "Subproject commit $submodule{$path}{right}");
 		}
 	}

 	# Symbolic links require special treatment. The standard "git diff"
 	# shows only the link itself, not the contents of the link target.
 	# This loop replicates that behavior.
 	for my $path (keys %symlink) {
 		if (defined($symlink{$path}{left})) {
 			write_to_file("$ldir/$path", $symlink{$path}{left});
 		}
 		if (defined($symlink{$path}{right})) {
 			write_to_file("$rdir/$path", $symlink{$path}{right});
 		}
 	}

 	return ($ldir, $rdir);
 }

 sub write_to_file
 {
 	my $path = shift;
 	my $value = shift;

 	# Make sure the path to the file exists
 	my $dir = dirname($path);
 	unless (-d "$dir") {
 		mkpath("$dir") or die $!;
 	}

 	# If the file already exists in that location, delete it.  This
 	# is required in the case of symbolic links.
 	unlink("$path");

 	open(my $fh, '>', "$path") or die $!;
 	print($fh $value);
 	close($fh);
 }

 # parse command-line options. all unrecognized options and arguments
 # are passed through to the 'git diff' command.
 my ($difftool_cmd, $dirdiff, $extcmd, $gui, $help, $prompt, $tool_help);
 GetOptions('g|gui!' => \$gui,
 	'd|dir-diff' => \$dirdiff,
 	'h' => \$help,
 	'prompt!' => \$prompt,
 	'y' => sub { $prompt = 0; },
 	't|tool:s' => \$difftool_cmd,
 	'tool-help' => \$tool_help,
 	'x|extcmd:s' => \$extcmd);

 if (defined($help)) {
 	usage(0);
 }
 if (defined($tool_help)) {
 	print_tool_help();
 }
 if (defined($difftool_cmd)) {
 	if (length($difftool_cmd) > 0) {
 		$ENV{GIT_DIFF_TOOL} = $difftool_cmd;
 	} else {
 		print "No <tool> given for --tool=<tool>\n";
 		usage(1);
 	}
 }
 if (defined($extcmd)) {
 	if (length($extcmd) > 0) {
 		$ENV{GIT_DIFFTOOL_EXTCMD} = $extcmd;
 	} else {
 		print "No <cmd> given for --extcmd=<cmd>\n";
 		usage(1);
 	}
 }
 if ($gui) {
 	my $guitool = '';
 	$guitool = Git::config('diff.guitool');
 	if (length($guitool) > 0) {
 		$ENV{GIT_DIFF_TOOL} = $guitool;
 	}
 }

 # In directory diff mode, 'git-difftool--helper' is called once
 # to compare the a/b directories.  In file diff mode, 'git diff'
 # will invoke a separate instance of 'git-difftool--helper' for
 # each file that changed.
 if (defined($dirdiff)) {
 	my ($a, $b) = setup_dir_diff();
 	if (defined($extcmd)) {
 		$rc = system($extcmd, $a, $b);
 	} else {
 		$ENV{GIT_DIFFTOOL_DIRDIFF} = 'true';
 		$rc = system('git', 'difftool--helper', $a, $b);
 	}

 	exit($rc | ($rc >> 8)) if ($rc != 0);

 	# If the diff including working copy files and those
 	# files were modified during the diff, then the changes
 	# should be copied back to the working tree
 	for my $file (@working_tree) {
 		if (-e "$b/$file" && compare("$b/$file", "$workdir/$file")) {
 			copy("$b/$file", "$workdir/$file") or die $!;
 			chmod(stat("$b/$file")->mode, "$workdir/$file") or die $!;
 		}
 	}
 } else {
 	if (defined($prompt)) {
 		if ($prompt) {
 			$ENV{GIT_DIFFTOOL_PROMPT} = 'true';
 		} else {
 			$ENV{GIT_DIFFTOOL_NO_PROMPT} = 'true';
 		}
 	}

 	$ENV{GIT_PAGER} = '';
 	$ENV{GIT_EXTERNAL_DIFF} = 'git-difftool--helper';

 	# ActiveState Perl for Win32 does not implement POSIX semantics of
 	# exec* system call. It just spawns the given executable and finishes
 	# the starting program, exiting with code 0.
 	# system will at least catch the errors returned by git diff,
 	# allowing the caller of git difftool better handling of failures.
 	my $rc = system('git', 'diff', @ARGV);
 	exit($rc | ($rc >> 8));
 }
	#!/usr/bin/perl
	# Copyright (c) 2009, 2010 David Aguilar
	# Copyright (c) 2012 Tim Henigan
	#
	# This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
	# git-difftool--helper script.
	#
	# This script exports GIT_EXTERNAL_DIFF and GIT_PAGER for use by git.
	# The GIT_DIFF* variables are exported for use by git-difftool--helper.
	#
	# Any arguments that are unknown to this script are forwarded to 'git diff'.

	use 5.008;
	use strict;
	use warnings;
	use File::Basename qw(dirname);
	use File::Copy;
	use File::Compare;
	use File::Find;
	use File::stat;
	use File::Path qw(mkpath);
	use File::Temp qw(tempdir);
	use Getopt::Long qw(:config pass_through);
	use Git;

	my @tools;
	my @working_tree;
	my $rc;
	my $repo = Git->repository();
	my $repo_path = $repo->repo_path();

	sub usage
	{
	my $exitcode = shift;
	print << 'USAGE';
	usage: git difftool [-t\|--tool=<tool>] [--tool-help]
	[-x\|--extcmd=<cmd>]
	[-g\|--gui] [--no-gui]
	[--prompt] [-y\|--no-prompt]
	[-d\|--dir-diff]
	['git diff' options]
	USAGE
	exit($exitcode);
	}

	sub find_worktree
	{
	# Git->repository->wc_path() does not honor changes to the working
	# tree location made by $ENV{GIT_WORK_TREE} or the 'core.worktree'
	# config variable.
	my $worktree;
	my $env_worktree = $ENV{GIT_WORK_TREE};
	my $core_worktree = Git::config('core.worktree');

	if (defined($env_worktree) and (length($env_worktree) > 0)) {
	$worktree = $env_worktree;
	} elsif (defined($core_worktree) and (length($core_worktree) > 0)) {
	$worktree = $core_worktree;
	} else {
	$worktree = $repo->wc_path();
	}

	return $worktree;
	}

	my $workdir = find_worktree();

	sub filter_tool_scripts
	{
	if (-d $_) {
	if ($_ ne ".") {
	# Ignore files in subdirectories
	$File::Find::prune = 1;
	}
	} else {
	if ((-f $_) && ($_ ne "defaults")) {
	push(@tools, $_);
	}
	}
	}

	sub print_tool_help
	{
	my ($cmd, @found, @notfound);
	my $gitpath = Git::exec_path();

	find(\&filter_tool_scripts, "$gitpath/mergetools");

	foreach my $tool (@tools) {
	$cmd = "TOOL_MODE=diff";
	$cmd .= ' && . "$(git --exec-path)/git-mergetool--lib"';
	$cmd .= " && get_merge_tool_path $tool >/dev/null 2>&1";
	$cmd .= " && can_diff >/dev/null 2>&1";
	if (system('sh', '-c', $cmd) == 0) {
	push(@found, $tool);
	} else {
	push(@notfound, $tool);
	}
	}

	print "'git difftool --tool=<tool>' may be set to one of the following:\n";
	print "\t$_\n" for (sort(@found));

	print "\nThe following tools are valid, but not currently available:\n";
	print "\t$_\n" for (sort(@notfound));

	print "\nNOTE: Some of the tools listed above only work in a windowed\n";
	print "environment. If run in a terminal-only session, they will fail.\n";

	exit(0);
	}

	sub setup_dir_diff
	{
	# Run the diff; exit immediately if no diff found
	# 'Repository' and 'WorkingCopy' must be explicitly set to insure that
	# if $GIT_DIR and $GIT_WORK_TREE are set in ENV, they are actually used
	# by Git->repository->command*.
	my $diffrepo = Git->repository(Repository => $repo_path, WorkingCopy => $workdir);
	my $diffrtn = $diffrepo->command_oneline('diff', '--raw', '--no-abbrev', '-z', @ARGV);
	exit(0) if (length($diffrtn) == 0);

	# Setup temp directories
	my $tmpdir = tempdir('git-diffall.XXXXX', CLEANUP => 1, TMPDIR => 1);
	my $ldir = "$tmpdir/left";
	my $rdir = "$tmpdir/right";
	mkpath($ldir) or die $!;
	mkpath($rdir) or die $!;

	# Build index info for left and right sides of the diff
	my $submodule_mode = '160000';
	my $symlink_mode = '120000';
	my $null_mode = '0' x 6;
	my $null_sha1 = '0' x 40;
	my $lindex = '';
	my $rindex = '';
	my %submodule;
	my %symlink;
	my @rawdiff = split('\0', $diffrtn);

	my $i = 0;
	while ($i < $#rawdiff) {
	if ($rawdiff[$i] =~ /^::/) {
	print "Combined diff formats ('-c' and '--cc') are not supported in directory diff mode.\n";
	exit(1);
	}

	my ($lmode, $rmode, $lsha1, $rsha1, $status) = split(' ', substr($rawdiff[$i], 1));
	my $src_path = $rawdiff[$i + 1];
	my $dst_path;

	if ($status =~ /^[CR]/) {
	$dst_path = $rawdiff[$i + 2];
	$i += 3;
	} else {
	$dst_path = $src_path;
	$i += 2;
	}

	if (($lmode eq $submodule_mode) or ($rmode eq $submodule_mode)) {
	$submodule{$src_path}{left} = $lsha1;
	if ($lsha1 ne $rsha1) {
	$submodule{$dst_path}{right} = $rsha1;
	} else {
	$submodule{$dst_path}{right} = "$rsha1-dirty";
	}
	next;
	}

	if ($lmode eq $symlink_mode) {
	$symlink{$src_path}{left} = $diffrepo->command_oneline('show', "$lsha1");
	}

	if ($rmode eq $symlink_mode) {
	$symlink{$dst_path}{right} = $diffrepo->command_oneline('show', "$rsha1");
	}

	if (($lmode ne $null_mode) and ($status !~ /^C/)) {
	$lindex .= "$lmode $lsha1\t$src_path\0";
	}

	if ($rmode ne $null_mode) {
	if ($rsha1 ne $null_sha1) {
	$rindex .= "$rmode $rsha1\t$dst_path\0";
	} else {
	push(@working_tree, $dst_path);
	}
	}
	}

	# If $GIT_DIR is not set prior to calling 'git update-index' and
	# 'git checkout-index', then those commands will fail if difftool
	# is called from a directory other than the repo root.
	my $must_unset_git_dir = 0;
	if (not defined($ENV{GIT_DIR})) {
	$must_unset_git_dir = 1;
	$ENV{GIT_DIR} = $repo_path;
	}

	# Populate the left and right directories based on each index file
	my ($inpipe, $ctx);
	$ENV{GIT_INDEX_FILE} = "$tmpdir/lindex";
	($inpipe, $ctx) = $repo->command_input_pipe(qw/update-index -z --index-info/);
	print($inpipe $lindex);
	$repo->command_close_pipe($inpipe, $ctx);
	$rc = system('git', 'checkout-index', '--all', "--prefix=$ldir/");
	exit($rc \| ($rc >> 8)) if ($rc != 0);

	$ENV{GIT_INDEX_FILE} = "$tmpdir/rindex";
	($inpipe, $ctx) = $repo->command_input_pipe(qw/update-index -z --index-info/);
	print($inpipe $rindex);
	$repo->command_close_pipe($inpipe, $ctx);
	$rc = system('git', 'checkout-index', '--all', "--prefix=$rdir/");
	exit($rc \| ($rc >> 8)) if ($rc != 0);

	# If $GIT_DIR was explicitly set just for the update/checkout
	# commands, then it should be unset before continuing.
	delete($ENV{GIT_DIR}) if ($must_unset_git_dir);
	delete($ENV{GIT_INDEX_FILE});

	# Changes in the working tree need special treatment since they are
	# not part of the index
	for my $file (@working_tree) {
	my $dir = dirname($file);
	unless (-d "$rdir/$dir") {
	mkpath("$rdir/$dir") or die $!;
	}
	copy("$workdir/$file", "$rdir/$file") or die $!;
	chmod(stat("$workdir/$file")->mode, "$rdir/$file") or die $!;
	}

	# Changes to submodules require special treatment. This loop writes a
	# temporary file to both the left and right directories to show the
	# change in the recorded SHA1 for the submodule.
	for my $path (keys %submodule) {
	if (defined($submodule{$path}{left})) {
	write_to_file("$ldir/$path", "Subproject commit $submodule{$path}{left}");
	}
	if (defined($submodule{$path}{right})) {
	write_to_file("$rdir/$path", "Subproject commit $submodule{$path}{right}");
	}
	}

	# Symbolic links require special treatment. The standard "git diff"
	# shows only the link itself, not the contents of the link target.
	# This loop replicates that behavior.
	for my $path (keys %symlink) {
	if (defined($symlink{$path}{left})) {
	write_to_file("$ldir/$path", $symlink{$path}{left});
	}
	if (defined($symlink{$path}{right})) {
	write_to_file("$rdir/$path", $symlink{$path}{right});
	}
	}

	return ($ldir, $rdir);
	}

	sub write_to_file
	{
	my $path = shift;
	my $value = shift;

	# Make sure the path to the file exists
	my $dir = dirname($path);
	unless (-d "$dir") {
	mkpath("$dir") or die $!;
	}

	# If the file already exists in that location, delete it. This
	# is required in the case of symbolic links.
	unlink("$path");

	open(my $fh, '>', "$path") or die $!;
	print($fh $value);
	close($fh);
	}

	# parse command-line options. all unrecognized options and arguments
	# are passed through to the 'git diff' command.
	my ($difftool_cmd, $dirdiff, $extcmd, $gui, $help, $prompt, $tool_help);
	GetOptions('g\|gui!' => \$gui,
	'd\|dir-diff' => \$dirdiff,
	'h' => \$help,
	'prompt!' => \$prompt,
	'y' => sub { $prompt = 0; },
	't\|tool:s' => \$difftool_cmd,
	'tool-help' => \$tool_help,
	'x\|extcmd:s' => \$extcmd);

	if (defined($help)) {
	usage(0);
	}
	if (defined($tool_help)) {
	print_tool_help();
	}
	if (defined($difftool_cmd)) {
	if (length($difftool_cmd) > 0) {
	$ENV{GIT_DIFF_TOOL} = $difftool_cmd;
	} else {
	print "No <tool> given for --tool=<tool>\n";
	usage(1);
	}
	}
	if (defined($extcmd)) {
	if (length($extcmd) > 0) {
	$ENV{GIT_DIFFTOOL_EXTCMD} = $extcmd;
	} else {
	print "No <cmd> given for --extcmd=<cmd>\n";
	usage(1);
	}
	}
	if ($gui) {
	my $guitool = '';
	$guitool = Git::config('diff.guitool');
	if (length($guitool) > 0) {
	$ENV{GIT_DIFF_TOOL} = $guitool;
	}
	}

	# In directory diff mode, 'git-difftool--helper' is called once
	# to compare the a/b directories. In file diff mode, 'git diff'
	# will invoke a separate instance of 'git-difftool--helper' for
	# each file that changed.
	if (defined($dirdiff)) {
	my ($a, $b) = setup_dir_diff();
	if (defined($extcmd)) {
	$rc = system($extcmd, $a, $b);
	} else {
	$ENV{GIT_DIFFTOOL_DIRDIFF} = 'true';
	$rc = system('git', 'difftool--helper', $a, $b);
	}

	exit($rc \| ($rc >> 8)) if ($rc != 0);

	# If the diff including working copy files and those
	# files were modified during the diff, then the changes
	# should be copied back to the working tree
	for my $file (@working_tree) {
	if (-e "$b/$file" && compare("$b/$file", "$workdir/$file")) {
	copy("$b/$file", "$workdir/$file") or die $!;
	chmod(stat("$b/$file")->mode, "$workdir/$file") or die $!;
	}
	}
	} else {
	if (defined($prompt)) {
	if ($prompt) {
	$ENV{GIT_DIFFTOOL_PROMPT} = 'true';
	} else {
	$ENV{GIT_DIFFTOOL_NO_PROMPT} = 'true';
	}
	}

	$ENV{GIT_PAGER} = '';
	$ENV{GIT_EXTERNAL_DIFF} = 'git-difftool--helper';

	# ActiveState Perl for Win32 does not implement POSIX semantics of
	# exec* system call. It just spawns the given executable and finishes
	# the starting program, exiting with code 0.
	# system will at least catch the errors returned by git diff,
	# allowing the caller of git difftool better handling of failures.
	my $rc = system('git', 'diff', @ARGV);
	exit($rc \| ($rc >> 8));
	}