Andrew's git / gitweb.git / git-cvsimport-script
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git-cvsimport-scripton commit cvsimport: Exit if an existing repository doesn't have the right branch. (4c24e08)
   1#!/usr/bin/perl -w
   2
   3# This tool is copyright (c) 2005, Matthias Urlichs.
   4# It is released under the Gnu Public License, version 2.
   5#
   6# The basic idea is to aggregate CVS check-ins into related changes.
   7# Fortunately, "cvsps" does that for us; all we have to do is to parse
   8# its output.
   9#
  10# Checking out the files is done by a single long-running CVS connection
  11# / server process.
  12#
  13# The head revision is on branch "origin" by default.
  14# You can change that with the '-o' option.
  15
  16use strict;
  17use warnings;
  18use Getopt::Std;
  19use File::Path qw(mkpath);
  20use File::Basename qw(basename dirname);
  21use Time::Local;
  22use IO::Socket;
  23use IO::Pipe;
  24use POSIX qw(strftime dup2);
  25
  26$SIG{'PIPE'}="IGNORE";
  27$ENV{'TZ'}="UTC";
  28
  29our($opt_h,$opt_o,$opt_v,$opt_d);
  30
  31sub usage() {
  32        print STDERR <<END;
  33Usage: ${\basename $0}     # fetch/update GIT from CVS
  34           [ -o branch-for-HEAD ] [ -h ] [ -v ] [ -d CVSROOT ]
  35       CVS_module [ GIT_repository ]
  36END
  37        exit(1);
  38}
  39
  40getopts("hqvo:d:") or usage();
  41usage if $opt_h;
  42
  43@ARGV == 1 or @ARGV == 2 or usage();
  44
  45my($cvs_tree, $git_tree) = @ARGV;
  46
  47if($opt_d) {
  48        $ENV{"CVSROOT"} = $opt_d;
  49} elsif($ENV{"CVSROOT"}) {
  50        $opt_d = $ENV{"CVSROOT"};
  51} else {
  52        die "CVSROOT needs to be set";
  53}
  54$opt_o ||= "origin";
  55$git_tree ||= ".";
  56
  57select(STDERR); $|=1; select(STDOUT);
  58
  59
  60package CVSconn;
  61# Basic CVS dialog.
  62# We're only interested in connecting and downloading, so ...
  63
  64use POSIX qw(strftime dup2);
  65
  66sub new {
  67        my($what,$repo,$subdir) = @_;
  68        $what=ref($what) if ref($what);
  69
  70        my $self = {};
  71        $self->{'buffer'} = "";
  72        bless($self,$what);
  73
  74        $repo =~ s#/+$##;
  75        $self->{'fullrep'} = $repo;
  76        $self->conn();
  77
  78        $self->{'subdir'} = $subdir;
  79        $self->{'lines'} = undef;
  80
  81        return $self;
  82}
  83
  84sub conn {
  85        my $self = shift;
  86        my $repo = $self->{'fullrep'};
  87        if($repo =~ s/^:pserver:(?:(.*?)(?::(.*?))?@)?([^:\/]*)(?::(\d*))?//) {
  88                my($user,$pass,$serv,$port) = ($1,$2,$3,$4);
  89                $user="anonymous" unless defined $user;
  90                my $rr2 = "-";
  91                unless($port) {
  92                        $rr2 = ":pserver:$user\@$serv:$repo";
  93                        $port=2401;
  94                }
  95                my $rr = ":pserver:$user\@$serv:$port$repo";
  96
  97                unless($pass) {
  98                        open(H,$ENV{'HOME'}."/.cvspass") and do {
  99                                # :pserver:cvs@mea.tmt.tele.fi:/cvsroot/zmailer Ah<Z
 100                                while(<H>) {
 101                                        chomp;
 102                                        s/^\/\d+\s+//;
 103                                        my ($w,$p) = split(/\s/,$_,2);
 104                                        if($w eq $rr or $w eq $rr2) {
 105                                                $pass = $p;
 106                                                last;
 107                                        }
 108                                }
 109                        };
 110                }
 111                $pass="A" unless $pass;
 112
 113                my $s = IO::Socket::INET->new(PeerHost => $serv, PeerPort => $port);
 114                die "Socket to $serv: $!\n" unless defined $s;
 115                $s->write("BEGIN AUTH REQUEST\n$repo\n$user\n$pass\nEND AUTH REQUEST\n")
 116                        or die "Write to $serv: $!\n";
 117                $s->flush();
 118
 119                my $rep = <$s>;
 120
 121                if($rep ne "I LOVE YOU\n") {
 122                        $rep="<unknown>" unless $rep;
 123                        die "AuthReply: $rep\n";
 124                }
 125                $self->{'socketo'} = $s;
 126                $self->{'socketi'} = $s;
 127        } else { # local: Fork off our own cvs server.
 128                my $pr = IO::Pipe->new();
 129                my $pw = IO::Pipe->new();
 130                my $pid = fork();
 131                die "Fork: $!\n" unless defined $pid;
 132                unless($pid) {
 133                        $pr->writer();
 134                        $pw->reader();
 135                        dup2($pw->fileno(),0);
 136                        dup2($pr->fileno(),1);
 137                        $pr->close();
 138                        $pw->close();
 139                        exec("cvs","server");
 140                }
 141                $pw->writer();
 142                $pr->reader();
 143                $self->{'socketo'} = $pw;
 144                $self->{'socketi'} = $pr;
 145        }
 146        $self->{'socketo'}->write("Root $repo\n");
 147
 148        # Trial and error says that this probably is the minimum set
 149        $self->{'socketo'}->write("Valid-responses ok error Valid-requests Mode M Mbinary E F Checked-in Created Updated Merged Removed\n");
 150
 151        $self->{'socketo'}->write("valid-requests\n");
 152        $self->{'socketo'}->flush();
 153
 154        chomp(my $rep=$self->readline());
 155        if($rep !~ s/^Valid-requests\s*//) {
 156                $rep="<unknown>" unless $rep;
 157                die "Expected Valid-requests from server, but got: $rep\n";
 158        }
 159        chomp(my $res=$self->readline());
 160        die "validReply: $res\n" if $res ne "ok";
 161
 162        $self->{'socketo'}->write("UseUnchanged\n") if $rep =~ /\bUseUnchanged\b/;
 163        $self->{'repo'} = $repo;
 164}
 165
 166sub readline {
 167        my($self) = @_;
 168        return $self->{'socketi'}->getline();
 169}
 170
 171sub _file {
 172        # Request a file with a given revision.
 173        # Trial and error says this is a good way to do it. :-/
 174        my($self,$fn,$rev) = @_;
 175        $self->{'socketo'}->write("Argument -N\n") or return undef;
 176        $self->{'socketo'}->write("Argument -P\n") or return undef;
 177        # $self->{'socketo'}->write("Argument -ko\n") or return undef;
 178        # -ko: Linus' version doesn't use it
 179        $self->{'socketo'}->write("Argument -r\n") or return undef;
 180        $self->{'socketo'}->write("Argument $rev\n") or return undef;
 181        $self->{'socketo'}->write("Argument --\n") or return undef;
 182        $self->{'socketo'}->write("Argument $self->{'subdir'}/$fn\n") or return undef;
 183        $self->{'socketo'}->write("Directory .\n") or return undef;
 184        $self->{'socketo'}->write("$self->{'repo'}\n") or return undef;
 185        # $self->{'socketo'}->write("Sticky T1.0\n") or return undef;
 186        $self->{'socketo'}->write("co\n") or return undef;
 187        $self->{'socketo'}->flush() or return undef;
 188        $self->{'lines'} = 0;
 189        return 1;
 190}
 191sub _line {
 192        # Read a line from the server.
 193        # ... except that 'line' may be an entire file. ;-)
 194        my($self) = @_;
 195        die "Not in lines" unless defined $self->{'lines'};
 196
 197        my $line;
 198        my $res="";
 199        while(defined($line = $self->readline())) {
 200                # M U gnupg-cvs-rep/AUTHORS
 201                # Updated gnupg-cvs-rep/
 202                # /daten/src/rsync/gnupg-cvs-rep/AUTHORS
 203                # /AUTHORS/1.1///T1.1
 204                # u=rw,g=rw,o=rw
 205                # 0
 206                # ok
 207
 208                if($line =~ s/^(?:Created|Updated) //) {
 209                        $line = $self->readline(); # path
 210                        $line = $self->readline(); # Entries line
 211                        my $mode = $self->readline(); chomp $mode;
 212                        $self->{'mode'} = $mode;
 213                        defined (my $cnt = $self->readline())
 214                                or die "EOF from server after 'Changed'\n";
 215                        chomp $cnt;
 216                        die "Duh: Filesize $cnt" if $cnt !~ /^\d+$/;
 217                        $line="";
 218                        $res="";
 219                        while($cnt) {
 220                                my $buf;
 221                                my $num = $self->{'socketi'}->read($buf,$cnt);
 222                                die "Server: Filesize $cnt: $num: $!\n" if not defined $num or $num<=0;
 223                                $res .= $buf;
 224                                $cnt -= $num;
 225                        }
 226                } elsif($line =~ s/^ //) {
 227                        $res .= $line;
 228                } elsif($line =~ /^M\b/) {
 229                        # output, do nothing
 230                } elsif($line =~ /^Mbinary\b/) {
 231                        my $cnt;
 232                        die "EOF from server after 'Mbinary'" unless defined ($cnt = $self->readline());
 233                        chomp $cnt;
 234                        die "Duh: Mbinary $cnt" if $cnt !~ /^\d+$/ or $cnt<1;
 235                        $line="";
 236                        while($cnt) {
 237                                my $buf;
 238                                my $num = $self->{'socketi'}->read($buf,$cnt);
 239                                die "S: Mbinary $cnt: $num: $!\n" if not defined $num or $num<=0;
 240                                $res .= $buf;
 241                                $cnt -= $num;
 242                        }
 243                } else {
 244                        chomp $line;
 245                        if($line eq "ok") {
 246                                # print STDERR "S: ok (".length($res).")\n";
 247                                return $res;
 248                        } elsif($line =~ s/^E //) {
 249                                # print STDERR "S: $line\n";
 250                        } else {
 251                                die "Unknown: $line\n";
 252                        }
 253                }
 254        }
 255}
 256sub file {
 257        my($self,$fn,$rev) = @_;
 258        my $res;
 259
 260        if ($self->_file($fn,$rev)) {
 261                $res = $self->_line();
 262                return $res if defined $res;
 263        }
 264
 265        # retry
 266        $self->conn();
 267        $self->_file($fn,$rev)
 268                or die "No file command send\n";
 269        $res = $self->_line();
 270        die "No input: $fn $rev\n" unless defined $res;
 271        return $res;
 272}
 273
 274
 275package main;
 276
 277my $cvs = CVSconn->new($opt_d, $cvs_tree);
 278
 279
 280sub pdate($) {
 281        my($d) = @_;
 282        m#(\d{2,4})/(\d\d)/(\d\d)\s(\d\d):(\d\d)(?::(\d\d))?#
 283                or die "Unparseable date: $d\n";
 284        my $y=$1; $y-=1900 if $y>1900;
 285        return timegm($6||0,$5,$4,$3,$2-1,$y);
 286}
 287
 288sub pmode($) {
 289        my($mode) = @_;
 290        my $m = 0;
 291        my $mm = 0;
 292        my $um = 0;
 293        for my $x(split(//,$mode)) {
 294                if($x eq ",") {
 295                        $m |= $mm&$um;
 296                        $mm = 0;
 297                        $um = 0;
 298                } elsif($x eq "u") { $um |= 0700;
 299                } elsif($x eq "g") { $um |= 0070;
 300                } elsif($x eq "o") { $um |= 0007;
 301                } elsif($x eq "r") { $mm |= 0444;
 302                } elsif($x eq "w") { $mm |= 0222;
 303                } elsif($x eq "x") { $mm |= 0111;
 304                } elsif($x eq "=") { # do nothing
 305                } else { die "Unknown mode: $mode\n";
 306                }
 307        }
 308        $m |= $mm&$um;
 309        return $m;
 310}
 311
 312my $tmpcv = "/var/cache/cvs";
 313
 314sub getwd() {
 315        my $pwd = `pwd`;
 316        chomp $pwd;
 317        return $pwd;
 318}
 319
 320-d $git_tree
 321        or mkdir($git_tree,0777)
 322        or die "Could not create $git_tree: $!";
 323chdir($git_tree);
 324
 325my $last_branch = "";
 326my $orig_branch = "";
 327my %branch_date;
 328
 329my $git_dir = $ENV{"GIT_DIR"} || ".git";
 330$git_dir = getwd()."/".$git_dir unless $git_dir =~ m#^/#;
 331$ENV{"GIT_DIR"} = $git_dir;
 332unless(-d $git_dir) {
 333        system("git-init-db");
 334        die "Cannot init the GIT db at $git_tree: $?\n" if $?;
 335        system("git-read-tree");
 336        die "Cannot init an empty tree: $?\n" if $?;
 337
 338        $last_branch = $opt_o;
 339        $orig_branch = "";
 340} else {
 341        -f "$git_dir/refs/head/$opt_o"
 342                or die "Branch '$opt_o' does not exist.\n".
 343                       "Either use the correct '-o branch' option,\n".
 344                       "or import to a new repository.\n";
 345
 346        $last_branch = basename(readlink("$git_dir/HEAD"));
 347        unless($last_branch) {
 348                warn "Cannot read the last branch name: $! -- assuming 'master'\n";
 349                $last_branch = "master";
 350        }
 351        $orig_branch = $last_branch;
 352
 353        # Get the last import timestamps
 354        opendir(D,"$git_dir/refs/heads");
 355        while(defined(my $head = readdir(D))) {
 356                next if $head =~ /^\./;
 357                open(F,"$git_dir/refs/heads/$head")
 358                        or die "Bad head branch: $head: $!\n";
 359                chomp(my $ftag = <F>);
 360                close(F);
 361                open(F,"git-cat-file commit $ftag |");
 362                while(<F>) {
 363                        next unless /^author\s.*\s(\d+)\s[-+]\d{4}$/;
 364                        $branch_date{$head} = $1;
 365                        last;
 366                }
 367                close(F);
 368        }
 369        closedir(D);
 370}
 371
 372-d $git_dir
 373        or die "Could not create git subdir ($git_dir).\n";
 374
 375my $pid = open(CVS,"-|");
 376die "Cannot fork: $!\n" unless defined $pid;
 377unless($pid) {
 378        exec("cvsps","-A","--cvs-direct",$cvs_tree);
 379        die "Could not start cvsps: $!\n";
 380}
 381
 382
 383## cvsps output:
 384#---------------------
 385#PatchSet 314
 386#Date: 1999/09/18 13:03:59
 387#Author: wkoch
 388#Branch: STABLE-BRANCH-1-0
 389#Ancestor branch: HEAD
 390#Tag: (none)
 391#Log:
 392#    See ChangeLog: Sat Sep 18 13:03:28 CEST 1999  Werner Koch
 393#Members:
 394#       README:1.57->1.57.2.1
 395#       VERSION:1.96->1.96.2.1
 396#
 397#---------------------
 398
 399my $state = 0;
 400
 401my($patchset,$date,$author,$branch,$ancestor,$tag,$logmsg);
 402my(@old,@new);
 403my $commit = sub {
 404        my $pid;
 405        while(@old) {
 406                my @o2;
 407                if(@old > 55) {
 408                        @o2 = splice(@old,0,50);
 409                } else {
 410                        @o2 = @old;
 411                        @old = ();
 412                }
 413                system("git-update-cache","--force-remove","--",@o2);
 414                die "Cannot remove files: $?\n" if $?;
 415        }
 416        while(@new) {
 417                my @n2;
 418                if(@new > 55) {
 419                        @n2 = splice(@new,0,50);
 420                } else {
 421                        @n2 = @new;
 422                        @new = ();
 423                }
 424                system("git-update-cache","--add","--",@n2);
 425                die "Cannot add files: $?\n" if $?;
 426        }
 427
 428        $pid = open(C,"-|");
 429        die "Cannot fork: $!" unless defined $pid;
 430        unless($pid) {
 431                exec("git-write-tree");
 432                die "Cannot exec git-write-tree: $!\n";
 433        }
 434        chomp(my $tree = <C>);
 435        length($tree) == 40
 436                or die "Cannot get tree id ($tree): $!\n";
 437        close(C)
 438                or die "Error running git-write-tree: $?\n";
 439        print "Tree ID $tree\n" if $opt_v;
 440
 441        my $parent = "";
 442        if(open(C,"$git_dir/refs/heads/$last_branch")) {
 443                chomp($parent = <C>);
 444                close(C);
 445                length($parent) == 40
 446                        or die "Cannot get parent id ($parent): $!\n";
 447                print "Parent ID $parent\n" if $opt_v;
 448        }
 449
 450        my $pr = IO::Pipe->new();
 451        my $pw = IO::Pipe->new();
 452        $pid = fork();
 453        die "Fork: $!\n" unless defined $pid;
 454        unless($pid) {
 455                $pr->writer();
 456                $pw->reader();
 457                dup2($pw->fileno(),0);
 458                dup2($pr->fileno(),1);
 459                $pr->close();
 460                $pw->close();
 461
 462                my @par = ();
 463                @par = ("-p",$parent) if $parent;
 464                exec("env",
 465                        "GIT_AUTHOR_NAME=$author",
 466                        "GIT_AUTHOR_EMAIL=$author",
 467                        "GIT_AUTHOR_DATE=".strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date)),
 468                        "GIT_COMMITTER_NAME=$author",
 469                        "GIT_COMMITTER_EMAIL=$author",
 470                        "GIT_COMMITTER_DATE=".strftime("+0000 %Y-%m-%d %H:%M:%S",gmtime($date)),
 471                        "git-commit-tree", $tree,@par);
 472                die "Cannot exec git-commit-tree: $!\n";
 473        }
 474        $pw->writer();
 475        $pr->reader();
 476
 477        # compatibility with git2cvs
 478        substr($logmsg,32767) = "" if length($logmsg) > 32767;
 479        $logmsg =~ s/[\s\n]+\z//;
 480
 481        print $pw "$logmsg\n"
 482                or die "Error writing to git-commit-tree: $!\n";
 483        $pw->close();
 484
 485        print "Committed patch $patchset ($branch)\n" if $opt_v;
 486        chomp(my $cid = <$pr>);
 487        length($cid) == 40
 488                or die "Cannot get commit id ($cid): $!\n";
 489        print "Commit ID $cid\n" if $opt_v;
 490        $pr->close();
 491
 492        waitpid($pid,0);
 493        die "Error running git-commit-tree: $?\n" if $?;
 494
 495        open(C,">$git_dir/refs/heads/$branch")
 496                or die "Cannot open branch $branch for update: $!\n";
 497        print C "$cid\n"
 498                or die "Cannot write branch $branch for update: $!\n";
 499        close(C)
 500                or die "Cannot write branch $branch for update: $!\n";
 501
 502        if($tag) {
 503                open(C,">$git_dir/refs/tags/$tag")
 504                        or die "Cannot create tag $tag: $!\n";
 505                print C "$cid\n"
 506                        or die "Cannot write tag $branch: $!\n";
 507                close(C)
 508                        or die "Cannot write tag $branch: $!\n";
 509                print "Created tag '$tag' on '$branch'\n" if $opt_v;
 510        }
 511};
 512
 513while(<CVS>) {
 514        chomp;
 515        if($state == 0 and /^-+$/) {
 516                $state = 1;
 517        } elsif($state == 0) {
 518                $state = 1;
 519                redo;
 520        } elsif(($state==0 or $state==1) and s/^PatchSet\s+//) {
 521                $patchset = 0+$_;
 522                $state=2;
 523        } elsif($state == 2 and s/^Date:\s+//) {
 524                $date = pdate($_);
 525                unless($date) {
 526                        print STDERR "Could not parse date: $_\n";
 527                        $state=0;
 528                        next;
 529                }
 530                $state=3;
 531        } elsif($state == 3 and s/^Author:\s+//) {
 532                s/\s+$//;
 533                $author = $_;
 534                $state = 4;
 535        } elsif($state == 4 and s/^Branch:\s+//) {
 536                s/\s+$//;
 537                $branch = $_;
 538                $state = 5;
 539        } elsif($state == 5 and s/^Ancestor branch:\s+//) {
 540                s/\s+$//;
 541                $ancestor = $_;
 542                $ancestor = $opt_o if $ancestor eq "HEAD";
 543                $state = 6;
 544        } elsif($state == 5) {
 545                $ancestor = undef;
 546                $state = 6;
 547                redo;
 548        } elsif($state == 6 and s/^Tag:\s+//) {
 549                s/\s+$//;
 550                if($_ eq "(none)") {
 551                        $tag = undef;
 552                } else {
 553                        $tag = $_;
 554                }
 555                $state = 7;
 556        } elsif($state == 7 and /^Log:/) {
 557                $logmsg = "";
 558                $state = 8;
 559        } elsif($state == 8 and /^Members:/) {
 560                $branch = $opt_o if $branch eq "HEAD";
 561                if(defined $branch_date{$branch} and $branch_date{$branch} >= $date) {
 562                        # skip
 563                        print "skip patchset $patchset: $date before $branch_date{$branch}\n";
 564                        $state = 11;
 565                        next;
 566                }
 567                if($ancestor) {
 568                        if(-f "$git_dir/refs/heads/$branch") {
 569                                print STDERR "Branch $branch already exists!\n";
 570                                $state=11;
 571                                next;
 572                        }
 573                        unless(open(H,"$git_dir/refs/heads/$ancestor")) {
 574                                print STDERR "Branch $ancestor does not exist!\n";
 575                                $state=11;
 576                                next;
 577                        }
 578                        chomp(my $id = <H>);
 579                        close(H);
 580                        unless(open(H,"> $git_dir/refs/heads/$branch")) {
 581                                print STDERR "Could not create branch $branch: $!\n";
 582                                $state=11;
 583                                next;
 584                        }
 585                        print H "$id\n"
 586                                or die "Could not write branch $branch: $!";
 587                        close(H)
 588                                or die "Could not write branch $branch: $!";
 589                }
 590                if(($ancestor || $branch) ne $last_branch) {
 591                        print "Switching from $last_branch to $branch\n" if $opt_v;
 592                        system("git-read-tree","-m","-u","$last_branch","$branch");
 593                        die "read-tree failed: $?\n" if $?;
 594                }
 595                if($branch ne $last_branch) {
 596                        unlink("$git_dir/HEAD");
 597                        symlink("refs/heads/$branch","$git_dir/HEAD");
 598                        $last_branch = $branch;
 599                }
 600                $state = 9;
 601        } elsif($state == 8) {
 602                $logmsg .= "$_\n";
 603        } elsif($state == 9 and /^\s+(\S+):(INITIAL|\d(?:\.\d+)+)->(\d(?:\.\d+)+)\s*$/) {
 604#       VERSION:1.96->1.96.2.1
 605                my $init = ($2 eq "INITIAL");
 606                my $fn = $1;
 607                my $rev = $3;
 608                $fn =~ s#^/+##;
 609                my $data = $cvs->file($fn,$rev);
 610                print "".($init ? "New" : "Update")." $fn: ".length($data)." bytes.\n";
 611                mkpath(dirname($fn),$opt_v);
 612                open(F,"> ./$fn")
 613                        or die "Cannot create '$fn': $!\n";
 614                print F $data
 615                        or die "Cannot write to '$fn': $!\n";
 616                close(F)
 617                        or die "Cannot write to '$fn': $!\n";
 618                chmod(pmode($cvs->{'mode'}), $fn);
 619                push(@new,$fn); # may be resurrected!
 620        } elsif($state == 9 and /^\s+(\S+):\d(?:\.\d+)+->(\d(?:\.\d+)+)\(DEAD\)\s*$/) {
 621                my $fn = $1;
 622                $fn =~ s#^/+##;
 623                push(@old,$fn);
 624        } elsif($state == 9 and /^\s*$/) {
 625                $state = 10;
 626        } elsif(($state == 9 or $state == 10) and /^-+$/) {
 627                &$commit();
 628                $state = 1;
 629        } elsif($state == 11 and /^-+$/) {
 630                $state = 1;
 631        } elsif(/^-+$/) { # end of unknown-line processing
 632                $state = 1;
 633        } elsif($state != 11) { # ignore stuff when skipping
 634                print "* UNKNOWN LINE * $_\n";
 635        }
 636}
 637&$commit() if $branch and $state != 11;
 638
 639# Now switch back to the branch we were in before all of this happened
 640if($orig_branch) {
 641        print "DONE; switching back to $orig_branch\n" if $opt_v;
 642} else {
 643        $orig_branch = "master";
 644        print "DONE; creating $orig_branch branch\n" if $opt_v;
 645        system("cp","$git_dir/refs/heads/$opt_o","$git_dir/refs/heads/master")
 646                unless -f "$git_dir/refs/heads/master";
 647}
 648
 649system("git-read-tree","-m","-u","$last_branch","$orig_branch");
 650die "read-tree failed: $?\n" if $?;
 651
 652unlink("$git_dir/HEAD");
 653symlink("refs/heads/$orig_branch","$git_dir/HEAD");
 654