difftool: add a skeleton for the upcoming builtin

This adds a builtin difftool that still falls back to the legacy Perl
version, which has been renamed to `legacy-difftool`.

The idea is that the new, experimental, builtin difftool immediately hands
off to the legacy difftool for now, unless the config variable
difftool.useBuiltin is set to true.

This feature flag will be used in the upcoming Git for Windows v2.11.0
release, to allow early testers to opt-in to use the builtin difftool and
flesh out any bugs.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 0 insertions, 470 deletions

diff --git a/git-difftool.perl b/git-difftool.perl
deleted file mode 100755
index a5790d03a0..0000000000
--- a/git-difftool.perl
+++ /dev/null
@@ -1,470 +0,0 @@
-#!/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 Error qw(:try);
-use File::Basename qw(dirname);
-use File::Copy;
-use File::Find;
-use File::stat;
-use File::Path qw(mkpath rmtree);
-use File::Temp qw(tempdir);
-use Getopt::Long qw(:config pass_through);
-use Git;
-
-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 print_tool_help
-{
-	# See the comment at the bottom of file_diff() for the reason behind
-	# using system() followed by exit() instead of exec().
-	my $rc = system(qw(git mergetool --tool-help=diff));
-	exit($rc | ($rc >> 8));
-}
-
-sub exit_cleanup
-{
-	my ($tmpdir, $status) = @_;
-	my $errno = $!;
-	rmtree($tmpdir);
-	if ($status and $errno) {
-		my ($package, $file, $line) = caller();
-		warn "$file line $line: $errno\n";
-	}
-	exit($status | ($status >> 8));
-}
-
-sub use_wt_file
-{
-	my ($workdir, $file, $sha1) = @_;
-	my $null_sha1 = '0' x 40;
-
-	if (-l "$workdir/$file" || ! -e _) {
-		return (0, $null_sha1);
-	}
-
-	my $wt_sha1 = Git::command_oneline('hash-object', "$workdir/$file");
-	my $use = ($sha1 eq $null_sha1) || ($sha1 eq $wt_sha1);
-	return ($use, $wt_sha1);
-}
-
-sub changed_files
-{
-	my ($repo_path, $index, $worktree) = @_;
-	$ENV{GIT_INDEX_FILE} = $index;
-
-	my @gitargs = ('--git-dir', $repo_path, '--work-tree', $worktree);
-	my @refreshargs = (
-		@gitargs, 'update-index',
-		'--really-refresh', '-q', '--unmerged');
-	try {
-		Git::command_oneline(@refreshargs);
-	} catch Git::Error::Command with {};
-
-	my @diffargs = (@gitargs, 'diff-files', '--name-only', '-z');
-	my $line = Git::command_oneline(@diffargs);
-	my @files;
-	if (defined $line) {
-		@files = split('\0', $line);
-	} else {
-		@files = ();
-	}
-
-	delete($ENV{GIT_INDEX_FILE});
-
-	return map { $_ => 1 } @files;
-}
-
-sub setup_dir_diff
-{
-	my ($workdir, $symlinks) = @_;
-	my @gitargs = ('diff', '--raw', '--no-abbrev', '-z', @ARGV);
-	my $diffrtn = Git::command_oneline(@gitargs);
-	exit(0) unless defined($diffrtn);
-
-	# 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 $wtindex = '';
-	my %submodule;
-	my %symlink;
-	my @working_tree = ();
-	my %working_tree_dups = ();
-	my @rawdiff = split('\0', $diffrtn);
-
-	my $i = 0;
-	while ($i < $#rawdiff) {
-		if ($rawdiff[$i] =~ /^::/) {
-			warn << 'EOF';
-Combined diff formats ('-c' and '--cc') are not supported in
-directory diff mode ('-d' and '--dir-diff').
-EOF
-			exit(1);
-		}
-
-		my ($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} =
-				Git::command_oneline('show', $lsha1);
-		}
-
-		if ($rmode eq $symlink_mode) {
-			$symlink{$dst_path}{right} =
-				Git::command_oneline('show', $rsha1);
-		}
-
-		if ($lmode ne $null_mode and $status !~ /^C/) {
-			$lindex .= "$lmode $lsha1\t$src_path\0";
-		}
-
-		if ($rmode ne $null_mode) {
-			# Avoid duplicate working_tree entries
-			if ($working_tree_dups{$dst_path}++) {
-				next;
-			}
-			my ($use, $wt_sha1) =
-				use_wt_file($workdir, $dst_path, $rsha1);
-			if ($use) {
-				push @working_tree, $dst_path;
-				$wtindex .= "$rmode $wt_sha1\t$dst_path\0";
-			} else {
-				$rindex .= "$rmode $rsha1\t$dst_path\0";
-			}
-		}
-	}
-
-	# Setup temp directories
-	my $tmpdir = tempdir('git-difftool.XXXXX', CLEANUP => 0, TMPDIR => 1);
-	my $ldir = "$tmpdir/left";
-	my $rdir = "$tmpdir/right";
-	mkpath($ldir) or exit_cleanup($tmpdir, 1);
-	mkpath($rdir) or exit_cleanup($tmpdir, 1);
-
-	# Populate the left and right directories based on each index file
-	my ($inpipe, $ctx);
-	$ENV{GIT_INDEX_FILE} = "$tmpdir/lindex";
-	($inpipe, $ctx) =
-		Git::command_input_pipe('update-index', '-z', '--index-info');
-	print($inpipe $lindex);
-	Git::command_close_pipe($inpipe, $ctx);
-
-	my $rc = system('git', 'checkout-index', '--all', "--prefix=$ldir/");
-	exit_cleanup($tmpdir, $rc) if $rc != 0;
-
-	$ENV{GIT_INDEX_FILE} = "$tmpdir/rindex";
-	($inpipe, $ctx) =
-		Git::command_input_pipe('update-index', '-z', '--index-info');
-	print($inpipe $rindex);
-	Git::command_close_pipe($inpipe, $ctx);
-
-	$rc = system('git', 'checkout-index', '--all', "--prefix=$rdir/");
-	exit_cleanup($tmpdir, $rc) if $rc != 0;
-
-	$ENV{GIT_INDEX_FILE} = "$tmpdir/wtindex";
-	($inpipe, $ctx) =
-		Git::command_input_pipe('update-index', '--info-only', '-z', '--index-info');
-	print($inpipe $wtindex);
-	Git::command_close_pipe($inpipe, $ctx);
-
-	# If $GIT_DIR was explicitly set just for the update/checkout
-	# commands, then it should be unset before continuing.
-	delete($ENV{GIT_INDEX_FILE});
-
-	# Changes in the working tree need special treatment since they are
-	# not part of the index. Remove any trailing slash from $workdir
-	# before starting to avoid double slashes in symlink targets.
-	$workdir =~ s|/$||;
-	for my $file (@working_tree) {
-		my $dir = dirname($file);
-		unless (-d "$rdir/$dir") {
-			mkpath("$rdir/$dir") or
-			exit_cleanup($tmpdir, 1);
-		}
-		if ($symlinks) {
-			symlink("$workdir/$file", "$rdir/$file") or
-			exit_cleanup($tmpdir, 1);
-		} else {
-			copy("$workdir/$file", "$rdir/$file") or
-			exit_cleanup($tmpdir, 1);
-
-			my $mode = stat("$workdir/$file")->mode;
-			chmod($mode, "$rdir/$file") or
-			exit_cleanup($tmpdir, 1);
-		}
-	}
-
-	# 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) {
-		my $ok = 0;
-		if (defined($submodule{$path}{left})) {
-			$ok = write_to_file("$ldir/$path",
-				"Subproject commit $submodule{$path}{left}");
-		}
-		if (defined($submodule{$path}{right})) {
-			$ok = write_to_file("$rdir/$path",
-				"Subproject commit $submodule{$path}{right}");
-		}
-		exit_cleanup($tmpdir, 1) if not $ok;
-	}
-
-	# 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) {
-		my $ok = 0;
-		if (defined($symlink{$path}{left})) {
-			$ok = write_to_file("$ldir/$path",
-					$symlink{$path}{left});
-		}
-		if (defined($symlink{$path}{right})) {
-			$ok = write_to_file("$rdir/$path",
-					$symlink{$path}{right});
-		}
-		exit_cleanup($tmpdir, 1) if not $ok;
-	}
-
-	return ($ldir, $rdir, $tmpdir, @working_tree);
-}
-
-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 return 0;
-	}
-
-	# If the file already exists in that location, delete it.  This
-	# is required in the case of symbolic links.
-	unlink($path);
-
-	open(my $fh, '>', $path) or return 0;
-	print($fh $value);
-	close($fh);
-
-	return 1;
-}
-
-sub main
-{
-	# parse command-line options. all unrecognized options and arguments
-	# are passed through to the 'git diff' command.
-	my %opts = (
-		difftool_cmd => undef,
-		dirdiff => undef,
-		extcmd => undef,
-		gui => undef,
-		help => undef,
-		prompt => undef,
-		symlinks => $^O ne 'cygwin' &&
-				$^O ne 'MSWin32' && $^O ne 'msys',
-		tool_help => undef,
-		trust_exit_code => undef,
-	);
-	GetOptions('g|gui!' => \$opts{gui},
-		'd|dir-diff' => \$opts{dirdiff},
-		'h' => \$opts{help},
-		'prompt!' => \$opts{prompt},
-		'y' => sub { $opts{prompt} = 0; },
-		'symlinks' => \$opts{symlinks},
-		'no-symlinks' => sub { $opts{symlinks} = 0; },
-		't|tool:s' => \$opts{difftool_cmd},
-		'tool-help' => \$opts{tool_help},
-		'trust-exit-code' => \$opts{trust_exit_code},
-		'no-trust-exit-code' => sub { $opts{trust_exit_code} = 0; },
-		'x|extcmd:s' => \$opts{extcmd});
-
-	if (defined($opts{help})) {
-		usage(0);
-	}
-	if (defined($opts{tool_help})) {
-		print_tool_help();
-	}
-	if (defined($opts{difftool_cmd})) {
-		if (length($opts{difftool_cmd}) > 0) {
-			$ENV{GIT_DIFF_TOOL} = $opts{difftool_cmd};
-		} else {
-			print "No <tool> given for --tool=<tool>\n";
-			usage(1);
-		}
-	}
-	if (defined($opts{extcmd})) {
-		if (length($opts{extcmd}) > 0) {
-			$ENV{GIT_DIFFTOOL_EXTCMD} = $opts{extcmd};
-		} else {
-			print "No <cmd> given for --extcmd=<cmd>\n";
-			usage(1);
-		}
-	}
-	if ($opts{gui}) {
-		my $guitool = Git::config('diff.guitool');
-		if (defined($guitool) && length($guitool) > 0) {
-			$ENV{GIT_DIFF_TOOL} = $guitool;
-		}
-	}
-
-	if (!defined $opts{trust_exit_code}) {
-		$opts{trust_exit_code} = Git::config_bool('difftool.trustExitCode');
-	}
-	if ($opts{trust_exit_code}) {
-		$ENV{GIT_DIFFTOOL_TRUST_EXIT_CODE} = 'true';
-	} else {
-		$ENV{GIT_DIFFTOOL_TRUST_EXIT_CODE} = 'false';
-	}
-
-	# In directory diff mode, 'git-difftool--helper' is called once
-	# to compare the a/b directories.  In file diff mode, 'git diff'
-	# will invoke a separate instance of 'git-difftool--helper' for
-	# each file that changed.
-	if (defined($opts{dirdiff})) {
-		dir_diff($opts{extcmd}, $opts{symlinks});
-	} else {
-		file_diff($opts{prompt});
-	}
-}
-
-sub dir_diff
-{
-	my ($extcmd, $symlinks) = @_;
-	my $rc;
-	my $error = 0;
-	my $repo = Git->repository();
-	my $repo_path = $repo->repo_path();
-	my $workdir = $repo->wc_path();
-	my ($a, $b, $tmpdir, @worktree) = setup_dir_diff($workdir, $symlinks);
-
-	if (defined($extcmd)) {
-		$rc = system($extcmd, $a, $b);
-	} else {
-		$ENV{GIT_DIFFTOOL_DIRDIFF} = 'true';
-		$rc = system('git', 'difftool--helper', $a, $b);
-	}
-	# 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.
-	# Do not copy back files when symlinks are used and the
-	# external tool did not replace the original link with a file.
-	#
-	# These hashes are loaded lazily since they aren't needed
-	# in the common case of --symlinks and the difftool updating
-	# files through the symlink.
-	my %wt_modified;
-	my %tmp_modified;
-	my $indices_loaded = 0;
-
-	for my $file (@worktree) {
-		next if $symlinks && -l "$b/$file";
-		next if ! -f "$b/$file";
-
-		if (!$indices_loaded) {
-			%wt_modified = changed_files(
-				$repo_path, "$tmpdir/wtindex", $workdir);
-			%tmp_modified = changed_files(
-				$repo_path, "$tmpdir/wtindex", $b);
-			$indices_loaded = 1;
-		}
-
-		if (exists $wt_modified{$file} and exists $tmp_modified{$file}) {
-			my $errmsg = "warning: Both files modified: ";
-			$errmsg .= "'$workdir/$file' and '$b/$file'.\n";
-			$errmsg .= "warning: Working tree file has been left.\n";
-			$errmsg .= "warning:\n";
-			warn $errmsg;
-			$error = 1;
-		} elsif (exists $tmp_modified{$file}) {
-			my $mode = stat("$b/$file")->mode;
-			copy("$b/$file", "$workdir/$file") or
-			exit_cleanup($tmpdir, 1);
-
-			chmod($mode, "$workdir/$file") or
-			exit_cleanup($tmpdir, 1);
-		}
-	}
-	if ($error) {
-		warn "warning: Temporary files exist in '$tmpdir'.\n";
-		warn "warning: You may want to cleanup or recover these.\n";
-		exit(1);
-	} else {
-		exit_cleanup($tmpdir, $rc);
-	}
-}
-
-sub file_diff
-{
-	my ($prompt) = @_;
-
-	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));
-}
-
-main();