#!/usr/bin/perl

## tar archive frontend for git-fast-import
##
## For example:
##
##  mkdir project; cd project; git init
##  perl import-tars.perl *.tar.bz2
##  git whatchanged import-tars
##
## Use --metainfo to specify the extension for a meta data file, where
## import-tars can read the commit message and optionally author and
## committer information.
##
##  echo 'This is the commit message' > myfile.tar.bz2.msg
##  perl import-tars.perl --metainfo=msg myfile.tar.bz2

use strict;
use Getopt::Long;

my $metaext = '';

die "usage: import-tars [--metainfo=extension] *.tar.{gz,bz2,Z}\n"
        unless GetOptions('metainfo=s' => \$metaext) && @ARGV;

my $branch_name = 'import-tars';
my $branch_ref = "refs/heads/$branch_name";
my $author_name = $ENV{'GIT_AUTHOR_NAME'} || 'T Ar Creator';
my $author_email = $ENV{'GIT_AUTHOR_EMAIL'} || 'tar@example.com';
my $committer_name = $ENV{'GIT_COMMITTER_NAME'} || `git config --get user.name`;
my $committer_email = $ENV{'GIT_COMMITTER_EMAIL'} || `git config --get user.email`;

chomp($committer_name, $committer_email);

open(FI, '|-', 'git', 'fast-import', '--quiet')
        or die "Unable to start git fast-import: $!\n";
foreach my $tar_file (@ARGV)
{
        my $commit_time = time;
        $tar_file =~ m,([^/]+)$,;
        my $tar_name = $1;

        if ($tar_name =~ s/\.(tar\.gz|tgz)$//) {
                open(I, '-|', 'gunzip', '-c', $tar_file)
                        or die "Unable to gunzip -c $tar_file: $!\n";
        } elsif ($tar_name =~ s/\.(tar\.bz2|tbz2)$//) {
                open(I, '-|', 'bunzip2', '-c', $tar_file)
                        or die "Unable to bunzip2 -c $tar_file: $!\n";
        } elsif ($tar_name =~ s/\.tar\.Z$//) {
                open(I, '-|', 'uncompress', '-c', $tar_file)
                        or die "Unable to uncompress -c $tar_file: $!\n";
        } elsif ($tar_name =~ s/\.tar$//) {
                open(I, $tar_file) or die "Unable to open $tar_file: $!\n";
        } else {
                die "Unrecognized compression format: $tar_file\n";
        }

        my $author_time = 0;
        my $next_mark = 1;
        my $have_top_dir = 1;
        my ($top_dir, %files);

        while (read(I, $_, 512) == 512) {
                my ($name, $mode, $uid, $gid, $size, $mtime,
                        $chksum, $typeflag, $linkname, $magic,
                        $version, $uname, $gname, $devmajor, $devminor,
                        $prefix) = unpack 'Z100 Z8 Z8 Z8 Z12 Z12
                        Z8 Z1 Z100 Z6
                        Z2 Z32 Z32 Z8 Z8 Z*', $_;
                last unless length($name);
                if ($name eq '././@LongLink') {
                        # GNU tar extension
                        if (read(I, $_, 512) != 512) {
                                die ('Short archive');
                        }
                        $name = unpack 'Z257', $_;
                        next unless $name;

                        my $dummy;
                        if (read(I, $_, 512) != 512) {
                                die ('Short archive');
                        }
                        ($dummy, $mode, $uid, $gid, $size, $mtime,
                        $chksum, $typeflag, $linkname, $magic,
                        $version, $uname, $gname, $devmajor, $devminor,
                        $prefix) = unpack 'Z100 Z8 Z8 Z8 Z12 Z12
                        Z8 Z1 Z100 Z6
                        Z2 Z32 Z32 Z8 Z8 Z*', $_;
                }
                next if $name =~ m{/\z};
                $mode = oct $mode;
                $size = oct $size;
                $mtime = oct $mtime;
                next if $typeflag == 5; # directory

                print FI "blob\n", "mark :$next_mark\n";
                if ($typeflag == 2) { # symbolic link
                        print FI "data ", length($linkname), "\n", $linkname;
                        $mode = 0120000;
                } else {
                        print FI "data $size\n";
                        while ($size > 0 && read(I, $_, 512) == 512) {
                                print FI substr($_, 0, $size);
                                $size -= 512;
                        }
                }
                print FI "\n";

                my $path;
                if ($prefix) {
                        $path = "$prefix/$name";
                } else {
                        $path = "$name";
                }
                $files{$path} = [$next_mark++, $mode];

                $author_time = $mtime if $mtime > $author_time;
                $path =~ m,^([^/]+)/,;
                $top_dir = $1 unless $top_dir;
                $have_top_dir = 0 if $top_dir ne $1;
        }

        my $commit_msg = "Imported from $tar_file.";
        my $this_committer_name = $committer_name;
        my $this_committer_email = $committer_email;
        my $this_author_name = $author_name;
        my $this_author_email = $author_email;
        if ($metaext ne '') {
                # Optionally read a commit message from <filename.tar>.msg
                # Add a line on the form "Committer: name <e-mail>" to override
                # the committer and "Author: name <e-mail>" to override the
                # author for this tar ball.
                if (open MSG, '<', "${tar_file}.${metaext}") {
                        my $header_done = 0;
                        $commit_msg = '';
                        while (<MSG>) {
                                if (!$header_done && /^Committer:\s+([^<>]*)\s+<(.*)>\s*$/i) {
                                        $this_committer_name = $1;
                                        $this_committer_email = $2;
                                } elsif (!$header_done && /^Author:\s+([^<>]*)\s+<(.*)>\s*$/i) {
                                        $this_author_name = $1;
                                        $this_author_email = $2;
                                } elsif (!$header_done && /^$/) { # empty line ends header.
                                        $header_done = 1;
                                } else {
                                        $commit_msg .= $_;
                                        $header_done = 1;
                                }
                        }
                        close MSG;
                }
        }

        print FI <<EOF;
commit $branch_ref
author $this_author_name <$this_author_email> $author_time +0000
committer $this_committer_name <$this_committer_email> $commit_time +0000
data <<END_OF_COMMIT_MESSAGE
$commit_msg
END_OF_COMMIT_MESSAGE

deleteall
EOF

        foreach my $path (keys %files)
        {
                my ($mark, $mode) = @{$files{$path}};
                $path =~ s,^([^/]+)/,, if $have_top_dir;
                $mode = $mode & 0111 ? 0755 : 0644 unless $mode == 0120000;
                printf FI "M %o :%i %s\n", $mode, $mark, $path;
        }
        print FI "\n";

        print FI <<EOF;
tag $tar_name
from $branch_ref
tagger $author_name <$author_email> $author_time +0000
data <<END_OF_TAG_MESSAGE
Package $tar_name
END_OF_TAG_MESSAGE

EOF

        close I;
}
close FI;