git-archimport.perl

   1 #!/usr/bin/perl -w
   2 #
   3 # This tool is copyright (c) 2005, Martin Langhoff.
   4 # It is released under the Gnu Public License, version 2.
   5 #
   6 # The basic idea is to walk the output of tla abrowse,
   7 # fetch the changesets and apply them.
   8 #
   9
  10 =head1 Invocation
  11
  12     git-archimport [ -h ] [ -v ] [ -T ] [ -t tempdir ] <archive>/<branch> [ <archive>/<branch> ]
  13
  14 Imports a project from one or more Arch repositories. It will follow branches
  15 and repositories within the namespaces defined by the <archive/branch>
  16 parameters suppplied. If it cannot find the remote branch a merge comes from
  17 it will just import it as a regular commit. If it can find it, it will mark it
  18 as a merge whenever possible.
  19
  20 See man (1) git-archimport for more details.
  21
  22 =head1 TODO
  23
  24  - create tag objects instead of ref tags
  25  - audit shell-escaping of filenames
  26  - hide our private tags somewhere smarter
  27  - find a way to make "cat *patches | patch" safe even when patchfiles are missing newlines
  28
  29 =head1 Devel tricks
  30
  31 Add print in front of the shell commands invoked via backticks.
  32
  33 =cut
  34
  35 use strict;
  36 use warnings;
  37 use Getopt::Std;
  38 use File::Spec;
  39 use File::Temp qw(tempfile tempdir);
  40 use File::Path qw(mkpath);
  41 use File::Basename qw(basename dirname);
  42 use String::ShellQuote;
  43 use Time::Local;
  44 use IO::Socket;
  45 use IO::Pipe;
  46 use POSIX qw(strftime dup2);
  47 use Data::Dumper qw/ Dumper /;
  48 use IPC::Open2;
  49
  50 $SIG{'PIPE'}="IGNORE";
  51 $ENV{'TZ'}="UTC";
  52
  53 my $git_dir = $ENV{"GIT_DIR"} || ".git";
  54 $ENV{"GIT_DIR"} = $git_dir;
  55
  56 our($opt_h,$opt_v, $opt_T,
  57     $opt_C,$opt_t);
  58
  59 sub usage() {
  60     print STDERR <<END;
  61 Usage: ${\basename $0}     # fetch/update GIT from Arch
  62        [ -h ] [ -v ] [ -T ] [ -t tempdir ]
  63        repository/arch-branch [ repository/arch-branch] ...
  64 END
  65     exit(1);
  66 }
  67
  68 getopts("Thvt:") or usage();
  69 usage if $opt_h;
  70
  71 @ARGV >= 1 or usage();
  72 my @arch_roots = @ARGV;
  73
  74 my ($tmpdir, $tmpdirname) = tempdir('git-archimport-XXXXXX', TMPDIR => 1, CLEANUP => 1);
  75 my $tmp = $opt_t || 1;
  76 $tmp = tempdir('git-archimport-XXXXXX', TMPDIR => 1, CLEANUP => 1);
  77 $opt_v && print "+ Using $tmp as temporary directory\n";
  78
  79 my @psets  = ();                # the collection
  80 my %psets  = ();                # the collection, by name
  81
  82 my %rptags = ();                # my reverse private tags
  83                                 # to map a SHA1 to a commitid
  84
  85 foreach my $root (@arch_roots) {
  86     my ($arepo, $abranch) = split(m!/!, $root);
  87     open ABROWSE, "tla abrowse -f -A $arepo --desc --merges $abranch |"
  88         or die "Problems with tla abrowse: $!";
  89
  90     my %ps        = ();         # the current one
  91     my $mode      = '';
  92     my $lastseen  = '';
  93
  94     while (<ABROWSE>) {
  95         chomp;
  96
  97         # first record padded w 8 spaces
  98         if (s/^\s{8}\b//) {
  99
 100             # store the record we just captured
 101             if (%ps) {
 102                 my %temp = %ps; # break references
 103                 push (@psets, \%temp);
 104                 $psets{$temp{id}} = \%temp;
 105                 %ps = ();
 106             }
 107
 108             my ($id, $type) = split(m/\s{3}/, $_);
 109             $ps{id}   = $id;
 110             $ps{repo} = $arepo;
 111
 112             # deal with types
 113             if ($type =~ m/^\(simple changeset\)/) {
 114                 $ps{type} = 's';
 115             } elsif ($type eq '(initial import)') {
 116                 $ps{type} = 'i';
 117             } elsif ($type =~ m/^\(tag revision of (.+)\)/) {
 118                 $ps{type} = 't';
 119                 $ps{tag}  = $1;
 120             } else {
 121                 warn "Unknown type $type";
 122             }
 123             $lastseen = 'id';
 124         }
 125
 126         if (s/^\s{10}//) {
 127             # 10 leading spaces or more
 128             # indicate commit metadata
 129
 130             # date & author
 131             if ($lastseen eq 'id' && m/^\d{4}-\d{2}-\d{2}/) {
 132
 133                 my ($date, $authoremail) = split(m/\s{2,}/, $_);
 134                 $ps{date}   = $date;
 135                 $ps{date}   =~ s/\bGMT$//; # strip off trailign GMT
 136                 if ($ps{date} =~ m/\b\w+$/) {
 137                     warn 'Arch dates not in GMT?! - imported dates will be wrong';
 138                 }
 139
 140                 $authoremail =~ m/^(.+)\s(\S+)$/;
 141                 $ps{author} = $1;
 142                 $ps{email}  = $2;
 143
 144                 $lastseen = 'date';
 145
 146             } elsif ($lastseen eq 'date') {
 147                 # the only hint is position
 148                 # subject is after date
 149                 $ps{subj} = $_;
 150                 $lastseen = 'subj';
 151
 152             } elsif ($lastseen eq 'subj' && $_ eq 'merges in:') {
 153                 $ps{merges} = [];
 154                 $lastseen = 'merges';
 155
 156             } elsif ($lastseen eq 'merges' && s/^\s{2}//) {
 157                 push (@{$ps{merges}}, $_);
 158             } else {
 159                 warn 'more metadata after merges!?';
 160             }
 161
 162         }
 163     }
 164
 165     if (%ps) {
 166         my %temp = %ps;         # break references
 167         push (@psets, \%temp);
 168         $psets{ $temp{id} } = \%temp;
 169         %ps = ();
 170     }
 171     close ABROWSE;
 172 }                               # end foreach $root
 173
 174 ## Order patches by time
 175 @psets = sort {$a->{date}.$b->{id} cmp $b->{date}.$b->{id}} @psets;
 176
 177 #print Dumper \@psets;
 178
 179 ##
 180 ## TODO cleanup irrelevant patches
 181 ##      and put an initial import
 182 ##      or a full tag
 183 my $import = 0;
 184 unless (-d $git_dir) { # initial import
 185     if ($psets[0]{type} eq 'i' || $psets[0]{type} eq 't') {
 186         print "Starting import from $psets[0]{id}\n";
 187         `git-init-db`;
 188         die $! if $?;
 189         $import = 1;
 190     } else {
 191         die "Need to start from an import or a tag -- cannot use $psets[0]{id}";
 192     }
 193 } else {    # progressing an import
 194     # load the rptags
 195     opendir(DIR, "$git_dir/archimport/tags")
 196         || die "can't opendir: $!";
 197     while (my $file = readdir(DIR)) {
 198         # skip non-interesting-files
 199         next unless -f "$git_dir/archimport/tags/$file";
 200         next if     $file =~ m/--base-0$/; # don't care for base-0
 201         my $sha = ptag($file);
 202         chomp $sha;
 203         # reconvert the 3rd '--' sequence from the end
 204         # into a slash
 205         # $file = reverse $file;
 206         # $file =~ s!^(.+?--.+?--.+?--.+?)--(.+)$!$1/$2!;
 207         # $file = reverse $file;
 208         $rptags{$sha} = $file;
 209     }
 210     closedir DIR;
 211 }
 212
 213 # process patchsets
 214 foreach my $ps (@psets) {
 215
 216     $ps->{branch} =  branchname($ps->{id});
 217
 218     #
 219     # ensure we have a clean state
 220     #
 221     if (`git diff-files`) {
 222         die "Unclean tree when about to process $ps->{id} " .
 223             " - did we fail to commit cleanly before?";
 224     }
 225     die $! if $?;
 226
 227     #
 228     # skip commits already in repo
 229     #
 230     if (ptag($ps->{id})) {
 231       $opt_v && print "Skipping already imported: $ps->{id}\n";
 232       next;
 233     }
 234
 235     #
 236     # create the branch if needed
 237     #
 238     if ($ps->{type} eq 'i' && !$import) {
 239         die "Should not have more than one 'Initial import' per GIT import: $ps->{id}";
 240     }
 241
 242     unless ($import) { # skip for import
 243         if ( -e "$git_dir/refs/heads/$ps->{branch}") {
 244             # we know about this branch
 245             `git checkout    $ps->{branch}`;
 246         } else {
 247             # new branch! we need to verify a few things
 248             die "Branch on a non-tag!" unless $ps->{type} eq 't';
 249             my $branchpoint = ptag($ps->{tag});
 250             die "Tagging from unknown id unsupported: $ps->{tag}"
 251                 unless $branchpoint;
 252
 253             # find where we are supposed to branch from
 254             `git checkout -b $ps->{branch} $branchpoint`;
 255
 256             # If we trust Arch with the fact that this is just
 257             # a tag, and it does not affect the state of the tree
 258             # then we just tag and move on
 259             tag($ps->{id}, $branchpoint);
 260             ptag($ps->{id}, $branchpoint);
 261             print " * Tagged $ps->{id} at $branchpoint\n";
 262             next;
 263         }
 264         die $! if $?;
 265     }
 266
 267     #
 268     # Apply the import/changeset/merge into the working tree
 269     #
 270     if ($ps->{type} eq 'i' || $ps->{type} eq 't') {
 271         apply_import($ps) or die $!;
 272         $import=0;
 273     } elsif ($ps->{type} eq 's') {
 274         apply_cset($ps);
 275     }
 276
 277     #
 278     # prepare update git's index, based on what arch knows
 279     # about the pset, resolve parents, etc
 280     #
 281     my $tree;
 282
 283     my $commitlog = `tla cat-archive-log -A $ps->{repo} $ps->{id}`;
 284     die "Error in cat-archive-log: $!" if $?;
 285
 286     # parselog will git-add/rm files
 287     # and generally prepare things for the commit
 288     # NOTE: parselog will shell-quote filenames!
 289     my ($sum, $msg, $add, $del, $mod, $ren) = parselog($commitlog);
 290     my $logmessage = "$sum\n$msg";
 291
 292
 293     # imports don't give us good info
 294     # on added files. Shame on them
 295     if ($ps->{type} eq 'i' || $ps->{type} eq 't') {
 296         `find . -type f -print0 | grep -zv '^./$git_dir' | xargs -0 -l100 git-update-index --add`;
 297         `git-ls-files --deleted -z | xargs --no-run-if-empty -0 -l100 git-update-index --remove`;
 298     }
 299
 300     if (@$add) {
 301         while (@$add) {
 302             my @slice = splice(@$add, 0, 100);
 303             my $slice = join(' ', @slice);
 304             `git-update-index --add $slice`;
 305             die "Error in git-update-index --add: $!" if $?;
 306         }
 307     }
 308     if (@$del) {
 309         foreach my $file (@$del) {
 310             unlink $file or die "Problems deleting $file : $!";
 311         }
 312         while (@$del) {
 313             my @slice = splice(@$del, 0, 100);
 314             my $slice = join(' ', @slice);
 315             `git-update-index --remove $slice`;
 316             die "Error in git-update-index --remove: $!" if $?;
 317         }
 318     }
 319     if (@$ren) {                # renamed
 320         if (@$ren % 2) {
 321             die "Odd number of entries in rename!?";
 322         }
 323         ;
 324         while (@$ren) {
 325             my $from = pop @$ren;
 326             my $to   = pop @$ren;
 327
 328             unless (-d dirname($to)) {
 329                 mkpath(dirname($to)); # will die on err
 330             }
 331             #print "moving $from $to";
 332             `mv $from $to`;
 333             die "Error renaming $from $to : $!" if $?;
 334             `git-update-index --remove $from`;
 335             die "Error in git-update-index --remove: $!" if $?;
 336             `git-update-index --add $to`;
 337             die "Error in git-update-index --add: $!" if $?;
 338         }
 339
 340     }
 341     if (@$mod) {                # must be _after_ renames
 342         while (@$mod) {
 343             my @slice = splice(@$mod, 0, 100);
 344             my $slice = join(' ', @slice);
 345             `git-update-index $slice`;
 346             die "Error in git-update-index: $!" if $?;
 347         }
 348     }
 349
 350     # warn "errors when running git-update-index! $!";
 351     $tree = `git-write-tree`;
 352     die "cannot write tree $!" if $?;
 353     chomp $tree;
 354
 355
 356     #
 357     # Who's your daddy?
 358     #
 359     my @par;
 360     if ( -e "$git_dir/refs/heads/$ps->{branch}") {
 361         if (open HEAD, "<$git_dir/refs/heads/$ps->{branch}") {
 362             my $p = <HEAD>;
 363             close HEAD;
 364             chomp $p;
 365             push @par, '-p', $p;
 366         } else {
 367             if ($ps->{type} eq 's') {
 368                 warn "Could not find the right head for the branch $ps->{branch}";
 369             }
 370         }
 371     }
 372
 373     if ($ps->{merges}) {
 374         push @par, find_parents($ps);
 375     }
 376     my $par = join (' ', @par);
 377
 378     #
 379     # Commit, tag and clean state
 380     #
 381     $ENV{TZ}                  = 'GMT';
 382     $ENV{GIT_AUTHOR_NAME}     = $ps->{author};
 383     $ENV{GIT_AUTHOR_EMAIL}    = $ps->{email};
 384     $ENV{GIT_AUTHOR_DATE}     = $ps->{date};
 385     $ENV{GIT_COMMITTER_NAME}  = $ps->{author};
 386     $ENV{GIT_COMMITTER_EMAIL} = $ps->{email};
 387     $ENV{GIT_COMMITTER_DATE}  = $ps->{date};
 388
 389     my ($pid, $commit_rh, $commit_wh);
 390     $commit_rh = 'commit_rh';
 391     $commit_wh = 'commit_wh';
 392
 393     $pid = open2(*READER, *WRITER, "git-commit-tree $tree $par")
 394         or die $!;
 395     print WRITER $logmessage;   # write
 396     close WRITER;
 397     my $commitid = <READER>;    # read
 398     chomp $commitid;
 399     close READER;
 400     waitpid $pid,0;             # close;
 401
 402     if (length $commitid != 40) {
 403         die "Something went wrong with the commit! $! $commitid";
 404     }
 405     #
 406     # Update the branch
 407     #
 408     open  HEAD, ">$git_dir/refs/heads/$ps->{branch}";
 409     print HEAD $commitid;
 410     close HEAD;
 411     unlink ("$git_dir/HEAD");
 412     symlink("refs/heads/$ps->{branch}","$git_dir/HEAD");
 413
 414     # tag accordingly
 415     ptag($ps->{id}, $commitid); # private tag
 416     if ($opt_T || $ps->{type} eq 't' || $ps->{type} eq 'i') {
 417         tag($ps->{id}, $commitid);
 418     }
 419     print " * Committed $ps->{id}\n";
 420     print "   + tree   $tree\n";
 421     print "   + commit $commitid\n";
 422     $opt_v && print "   + commit date is  $ps->{date} \n";
 423     $opt_v && print "   + parents:  $par \n";
 424 }
 425
 426 sub branchname {
 427     my $id = shift;
 428     $id =~ s#^.+?/##;
 429     my @parts = split(m/--/, $id);
 430     return join('--', @parts[0..1]);
 431 }
 432
 433 sub apply_import {
 434     my $ps = shift;
 435     my $bname = branchname($ps->{id});
 436
 437     `mkdir -p $tmp`;
 438
 439     `tla get -s --no-pristine -A $ps->{repo} $ps->{id} $tmp/import`;
 440     die "Cannot get import: $!" if $?;
 441     `rsync -v --archive --delete --exclude '$git_dir' --exclude '.arch-ids' --exclude '{arch}' $tmp/import/* ./`;
 442     die "Cannot rsync import:$!" if $?;
 443
 444     `rm -fr $tmp/import`;
 445     die "Cannot remove tempdir: $!" if $?;
 446
 447
 448     return 1;
 449 }
 450
 451 sub apply_cset {
 452     my $ps = shift;
 453
 454     `mkdir -p $tmp`;
 455
 456     # get the changeset
 457     `tla get-changeset  -A $ps->{repo} $ps->{id} $tmp/changeset`;
 458     die "Cannot get changeset: $!" if $?;
 459
 460     # apply patches
 461     if (`find $tmp/changeset/patches -type f -name '*.patch'`) {
 462         # this can be sped up considerably by doing
 463         #    (find | xargs cat) | patch
 464         # but that cna get mucked up by patches
 465         # with missing trailing newlines or the standard
 466         # 'missing newline' flag in the patch - possibly
 467         # produced with an old/buggy diff.
 468         # slow and safe, we invoke patch once per patchfile
 469         `find $tmp/changeset/patches -type f -name '*.patch' -print0 | grep -zv '{arch}' | xargs -iFILE -0 --no-run-if-empty patch -p1 --forward -iFILE`;
 470         die "Problem applying patches! $!" if $?;
 471     }
 472
 473     # apply changed binary files
 474     if (my @modified = `find $tmp/changeset/patches -type f -name '*.modified'`) {
 475         foreach my $mod (@modified) {
 476             chomp $mod;
 477             my $orig = $mod;
 478             $orig =~ s/\.modified$//; # lazy
 479             $orig =~ s!^\Q$tmp\E/changeset/patches/!!;
 480             #print "rsync -p '$mod' '$orig'";
 481             `rsync -p $mod ./$orig`;
 482             die "Problem applying binary changes! $!" if $?;
 483         }
 484     }
 485
 486     # bring in new files
 487     `rsync --archive --exclude '$git_dir' --exclude '.arch-ids' --exclude '{arch}' $tmp/changeset/new-files-archive/* ./`;
 488
 489     # deleted files are hinted from the commitlog processing
 490
 491     `rm -fr $tmp/changeset`;
 492 }
 493
 494
 495 # =for reference
 496 # A log entry looks like
 497 # Revision: moodle-org--moodle--1.3.3--patch-15
 498 # Archive: arch-eduforge@catalyst.net.nz--2004
 499 # Creator: Penny Leach <penny@catalyst.net.nz>
 500 # Date: Wed May 25 14:15:34 NZST 2005
 501 # Standard-date: 2005-05-25 02:15:34 GMT
 502 # New-files: lang/de/.arch-ids/block_glossary_random.php.id
 503 #     lang/de/.arch-ids/block_html.php.id
 504 # New-directories: lang/de/help/questionnaire
 505 #     lang/de/help/questionnaire/.arch-ids
 506 # Renamed-files: .arch-ids/db_sears.sql.id db/.arch-ids/db_sears.sql.id
 507 #    db_sears.sql db/db_sears.sql
 508 # Removed-files: lang/be/docs/.arch-ids/release.html.id
 509 #     lang/be/docs/.arch-ids/releaseold.html.id
 510 # Modified-files: admin/cron.php admin/delete.php
 511 #     admin/editor.html backup/lib.php backup/restore.php
 512 # New-patches: arch-eduforge@catalyst.net.nz--2004/moodle-org--moodle--1.3.3--patch-15
 513 # Summary: Updating to latest from MOODLE_14_STABLE (1.4.5+)
 514 # Keywords:
 515 #
 516 # Updating yadda tadda tadda madda
 517 sub parselog {
 518     my $log = shift;
 519     #print $log;
 520
 521     my (@add, @del, @mod, @ren, @kw, $sum, $msg );
 522
 523     if ($log =~ m/(?:\n|^)New-files:(.*?)(?=\n\w)/s ) {
 524         my $files = $1;
 525         @add = split(m/\s+/s, $files);
 526     }
 527
 528     if ($log =~ m/(?:\n|^)Removed-files:(.*?)(?=\n\w)/s ) {
 529         my $files = $1;
 530         @del = split(m/\s+/s, $files);
 531     }
 532
 533     if ($log =~ m/(?:\n|^)Modified-files:(.*?)(?=\n\w)/s ) {
 534         my $files = $1;
 535         @mod = split(m/\s+/s, $files);
 536     }
 537
 538     if ($log =~ m/(?:\n|^)Renamed-files:(.*?)(?=\n\w)/s ) {
 539         my $files = $1;
 540         @ren = split(m/\s+/s, $files);
 541     }
 542
 543     $sum ='';
 544     if ($log =~ m/^Summary:(.+?)$/m ) {
 545         $sum = $1;
 546         $sum =~ s/^\s+//;
 547         $sum =~ s/\s+$//;
 548     }
 549
 550     $msg = '';
 551     if ($log =~ m/\n\n(.+)$/s) {
 552         $msg = $1;
 553         $msg =~ s/^\s+//;
 554         $msg =~ s/\s+$//;
 555     }
 556
 557
 558     # cleanup the arrays
 559     foreach my $ref ( (\@add, \@del, \@mod, \@ren) ) {
 560         my @tmp = ();
 561         while (my $t = pop @$ref) {
 562             next unless length ($t);
 563             next if $t =~ m!\{arch\}/!;
 564             next if $t =~ m!\.arch-ids/!;
 565             next if $t =~ m!\.arch-inventory$!;
 566             push (@tmp, shell_quote($t));
 567         }
 568         @$ref = @tmp;
 569     }
 570
 571     #print Dumper [$sum, $msg, \@add, \@del, \@mod, \@ren];
 572     return       ($sum, $msg, \@add, \@del, \@mod, \@ren);
 573 }
 574
 575 # write/read a tag
 576 sub tag {
 577     my ($tag, $commit) = @_;
 578     $tag =~ s|/|--|g;
 579     $tag = shell_quote($tag);
 580
 581     if ($commit) {
 582         open(C,">$git_dir/refs/tags/$tag")
 583             or die "Cannot create tag $tag: $!\n";
 584         print C "$commit\n"
 585             or die "Cannot write tag $tag: $!\n";
 586         close(C)
 587             or die "Cannot write tag $tag: $!\n";
 588         print " * Created tag ' $tag' on '$commit'\n" if $opt_v;
 589     } else {                    # read
 590         open(C,"<$git_dir/refs/tags/$tag")
 591             or die "Cannot read tag $tag: $!\n";
 592         $commit = <C>;
 593         chomp $commit;
 594         die "Error reading tag $tag: $!\n" unless length $commit == 40;
 595         close(C)
 596             or die "Cannot read tag $tag: $!\n";
 597         return $commit;
 598     }
 599 }
 600
 601 # write/read a private tag
 602 # reads fail softly if the tag isn't there
 603 sub ptag {
 604     my ($tag, $commit) = @_;
 605     $tag =~ s|/|--|g;
 606     $tag = shell_quote($tag);
 607
 608     unless (-d "$git_dir/archimport/tags") {
 609         mkpath("$git_dir/archimport/tags");
 610     }
 611
 612     if ($commit) {              # write
 613         open(C,">$git_dir/archimport/tags/$tag")
 614             or die "Cannot create tag $tag: $!\n";
 615         print C "$commit\n"
 616             or die "Cannot write tag $tag: $!\n";
 617         close(C)
 618             or die "Cannot write tag $tag: $!\n";
 619         $rptags{$commit} = $tag
 620             unless $tag =~ m/--base-0$/;
 621     } else {                    # read
 622         # if the tag isn't there, return 0
 623         unless ( -s "$git_dir/archimport/tags/$tag") {
 624             return 0;
 625         }
 626         open(C,"<$git_dir/archimport/tags/$tag")
 627             or die "Cannot read tag $tag: $!\n";
 628         $commit = <C>;
 629         chomp $commit;
 630         die "Error reading tag $tag: $!\n" unless length $commit == 40;
 631         close(C)
 632             or die "Cannot read tag $tag: $!\n";
 633         unless (defined $rptags{$commit}) {
 634             $rptags{$commit} = $tag;
 635         }
 636         return $commit;
 637     }
 638 }
 639
 640 sub find_parents {
 641     #
 642     # Identify what branches are merging into me
 643     # and whether we are fully merged
 644     # git-merge-base <headsha> <headsha> should tell
 645     # me what the base of the merge should be
 646     #
 647     my $ps = shift;
 648
 649     my %branches; # holds an arrayref per branch
 650                   # the arrayref contains a list of
 651                   # merged patches between the base
 652                   # of the merge and the current head
 653
 654     my @parents;  # parents found for this commit
 655
 656     # simple loop to split the merges
 657     # per branch
 658     foreach my $merge (@{$ps->{merges}}) {
 659         my $branch = branchname($merge);
 660         unless (defined $branches{$branch} ){
 661             $branches{$branch} = [];
 662         }
 663         push @{$branches{$branch}}, $merge;
 664     }
 665
 666     #
 667     # foreach branch find a merge base and walk it to the
 668     # head where we are, collecting the merged patchsets that
 669     # Arch has recorded. Keep that in @have
 670     # Compare that with the commits on the other branch
 671     # between merge-base and the tip of the branch (@need)
 672     # and see if we have a series of consecutive patches
 673     # starting from the merge base. The tip of the series
 674     # of consecutive patches merged is our new parent for
 675     # that branch.
 676     #
 677     foreach my $branch (keys %branches) {
 678         my $mergebase = `git-merge-base $branch $ps->{branch}`;
 679         die "Cannot find merge base for $branch and $ps->{branch}" if $?;
 680         chomp $mergebase;
 681
 682         # now walk up to the mergepoint collecting what patches we have
 683         my $branchtip = git_rev_parse($ps->{branch});
 684         my @ancestors = `git-rev-list --merge-order $branchtip ^$mergebase`;
 685         my %have; # collected merges this branch has
 686         foreach my $merge (@{$ps->{merges}}) {
 687             $have{$merge} = 1;
 688         }
 689         my %ancestorshave;
 690         foreach my $par (@ancestors) {
 691             $par = commitid2pset($par);
 692             if (defined $par->{merges}) {
 693                 foreach my $merge (@{$par->{merges}}) {
 694                     $ancestorshave{$merge}=1;
 695                 }
 696             }
 697         }
 698         # print "++++ Merges in $ps->{id} are....\n";
 699         # my @have = sort keys %have;   print Dumper(\@have);
 700
 701         # merge what we have with what ancestors have
 702         %have = (%have, %ancestorshave);
 703
 704         # see what the remote branch has - these are the merges we
 705         # will want to have in a consecutive series from the mergebase
 706         my $otherbranchtip = git_rev_parse($branch);
 707         my @needraw = `git-rev-list --merge-order $otherbranchtip ^$mergebase`;
 708         my @need;
 709         foreach my $needps (@needraw) {         # get the psets
 710             $needps = commitid2pset($needps);
 711             # git-rev-list will also
 712             # list commits merged in via earlier
 713             # merges. we are only interested in commits
 714             # from the branch we're looking at
 715             if ($branch eq $needps->{branch}) {
 716                 push @need, $needps->{id};
 717             }
 718         }
 719
 720         # print "++++ Merges from $branch we want are....\n";
 721         # print Dumper(\@need);
 722
 723         my $newparent;
 724         while (my $needed_commit = pop @need) {
 725             if ($have{$needed_commit}) {
 726                 $newparent = $needed_commit;
 727             } else {
 728                 last; # break out of the while
 729             }
 730         }
 731         if ($newparent) {
 732             push @parents, $newparent;
 733         }
 734
 735
 736     } # end foreach branch
 737
 738     # prune redundant parents
 739     my %parents;
 740     foreach my $p (@parents) {
 741         $parents{$p} = 1;
 742     }
 743     foreach my $p (@parents) {
 744         next unless exists $psets{$p}{merges};
 745         next unless ref    $psets{$p}{merges};
 746         my @merges = @{$psets{$p}{merges}};
 747         foreach my $merge (@merges) {
 748             if ($parents{$merge}) {
 749                 delete $parents{$merge};
 750             }
 751         }
 752     }
 753     @parents = keys %parents;
 754     @parents = map { " -p " . ptag($_) } @parents;
 755     return @parents;
 756 }
 757
 758 sub git_rev_parse {
 759     my $name = shift;
 760     my $val  = `git-rev-parse $name`;
 761     die "Error: git-rev-parse $name" if $?;
 762     chomp $val;
 763     return $val;
 764 }
 765
 766 # resolve a SHA1 to a known patchset
 767 sub commitid2pset {
 768     my $commitid = shift;
 769     chomp $commitid;
 770     my $name = $rptags{$commitid}
 771         || die "Cannot find reverse tag mapping for $commitid";
 772     # the keys in %rptag  are slightly munged; unmunge
 773     # reconvert the 3rd '--' sequence from the end
 774     # into a slash
 775     $name = reverse $name;
 776     $name =~ s!^(.+?--.+?--.+?--.+?)--(.+)$!$1/$2!;
 777     $name = reverse $name;
 778     my $ps   = $psets{$name}
 779         || (print Dumper(sort keys %psets)) && die "Cannot find patchset for $name";
 780     return $ps;
 781 }