difftool: Eliminate global variables

[alt-git.git] / git-difftool.perl

#!/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(basename dirname);
use File::Copy;
use File::Compare;
use File::stat;
use File::Path qw(mkpath);
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 find_worktree
{
        my ($repo) = @_;

        # 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;
}

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

        my @files = map { basename($_) } glob("$gitpath/mergetools/*");
        my @tools = sort(grep { !m{^defaults$} } @files);

        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 (@found);

        print "\nThe following tools are valid, but not currently available:\n";
        print "\t$_\n" for (@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
{
        my ($repo, $workdir) = @_;

        # 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 $repo_path = $repo->repo_path();
        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 @working_tree = ();
        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);
        my $rc = system('git', 'checkout-index', '--all', "--prefix=$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, @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 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);
}

sub main
{
        # 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($dirdiff)) {
                dir_diff($extcmd);
        } else {
                file_diff($prompt);
        }
}

sub dir_diff
{
        my ($extcmd) = @_;

        my $rc;
        my $repo = Git->repository();

        my $workdir = find_worktree($repo);
        my ($a, $b, @working_tree) = setup_dir_diff($repo, $workdir);
        if (defined($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 $!;
                }
        }
}

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();