+# only update last_commit for $i on reindex iff newer than current
+sub update_last_commit {
+ my ($self, $git, $i, $cmt) = @_;
+ my $last = $self->{mm}->last_commit_n($i);
+ if (defined $last && is_ancestor($git, $last, $cmt)) {
+ my @cmd = (qw(rev-list --count), "$last..$cmt");
+ chomp(my $n = $git->qx(@cmd));
+ return if $n ne '' && $n == 0;
+ }
+ $self->{mm}->last_commit_n($i, $cmt);
+}
+
+sub git_dir_n ($$) { "$_[0]->{-inbox}->{mainrepo}/git/$_[1].git" }
+
+sub last_commits {
+ my ($self, $max_git) = @_;
+ my $heads = [];
+ for (my $i = $max_git; $i >= 0; $i--) {
+ $heads->[$i] = $self->{mm}->last_commit_n($i);
+ }
+ $heads;
+}
+
+sub is_ancestor ($$$) {
+ my ($git, $cur, $tip) = @_;
+ return 0 unless $git->check($cur);
+ my $cmd = [ 'git', "--git-dir=$git->{git_dir}",
+ qw(merge-base --is-ancestor), $cur, $tip ];
+ my $pid = spawn($cmd);
+ defined $pid or die "spawning ".join(' ', @$cmd)." failed: $!";
+ waitpid($pid, 0) == $pid or die join(' ', @$cmd) .' did not finish';
+ $? == 0;
+}
+
+sub index_prepare {
+ my ($self, $opts, $max_git, $ranges) = @_;
+ my $regen_max = 0;
+ my $head = $self->{-inbox}->{ref_head} || 'refs/heads/master';
+ for (my $i = $max_git; $i >= 0; $i--) {
+ die "already indexing!\n" if $self->{index_pipe};
+ my $git_dir = git_dir_n($self, $i);
+ -d $git_dir or next; # missing parts are fine
+ my $git = PublicInbox::Git->new($git_dir);
+ chomp(my $tip = $git->qx('rev-parse', $head));
+ my $range;
+ if (defined(my $cur = $ranges->[$i])) {
+ $range = "$cur..$tip";
+ if (is_ancestor($git, $cur, $tip)) { # common case
+ my $n = $git->qx(qw(rev-list --count), $range);
+ chomp($n);
+ if ($n == 0) {
+ $ranges->[$i] = undef;
+ next;
+ }
+ } else {
+ warn <<"";
+discontiguous range: $range
+Rewritten history? (in $git_dir)
+
+ my $base = $git->qx('merge-base', $tip, $cur);
+ chomp $base;
+ if ($base) {
+ $range = "$base..$tip";
+ warn "found merge-base: $base\n"
+ } else {
+ $range = $tip;
+ warn <<"";
+discarding history at $cur
+
+ }
+ warn <<"";
+reindexing $git_dir starting at
+$range
+
+ $self->{"unindex-range.$i"} = "$base..$cur";
+ }
+ } else {
+ $range = $tip; # all of it
+ }
+ $ranges->[$i] = $range;
+
+ # can't use 'rev-list --count' if we use --diff-filter
+ my $fh = $git->popen(qw(log --pretty=tformat:%h
+ --no-notes --no-color --no-renames
+ --diff-filter=AM), $range, '--', 'm');
+ ++$regen_max while <$fh>;
+ }
+ \$regen_max;
+}
+
+sub unindex_oid {
+ my ($self, $git, $oid) = @_;
+ my $msgref = $git->cat_file($oid);
+ my $mime = PublicInbox::MIME->new($msgref);
+ my $mids = mids($mime->header_obj);
+ $mime = $msgref = undef;
+
+ foreach my $mid (@$mids) {
+ my %gone;
+ $self->{-inbox}->search->reopen->each_smsg_by_mid($mid, sub {
+ my ($smsg) = @_;
+ $smsg->load_expand;
+ $gone{$smsg->num} = 1 if $oid eq $smsg->{blob};
+ 1; # continue
+ });
+ my $n = scalar keys %gone;
+ next unless $n;
+ if ($n > 1) {
+ warn "BUG: multiple articles linked to $oid\n",
+ join(',',sort keys %gone), "\n";
+ }
+ $self->{unindexed}->{$_}++ foreach keys %gone;
+ $_->remote_remove($oid, $mid) foreach @{$self->{idx_parts}};
+ $self->{over}->remove_oid($oid, $mid);
+ $self->barrier;
+ }
+}
+
+my $x40 = qr/[a-f0-9]{40}/;
+sub unindex {
+ my ($self, $opts, $git, $unindex_range) = @_;
+ my $un = $self->{unindexed} ||= {}; # num => removal count
+ $self->barrier;
+ my $before = scalar keys %$un;
+ my @cmd = qw(log --raw -r
+ --no-notes --no-color --no-abbrev --no-renames);
+ my $fh = $self->{reindex_pipe} = $git->popen(@cmd, $unindex_range);
+ while (<$fh>) {
+ /\A:\d{6} 100644 $x40 ($x40) [AM]\tm$/o or next;
+ $self->unindex_oid($git, $1);
+ }
+ delete $self->{reindex_pipe};
+ $fh = undef;
+
+ return unless $opts->{prune};
+ my $after = scalar keys %$un;
+ return if $before == $after;
+
+ # ensure any blob can not longer be accessed via dumb HTTP
+ PublicInbox::Import::run_die(['git', "--git-dir=$git->{git_dir}",
+ qw(-c gc.reflogExpire=now gc --prune=all)]);
+}
+
+sub index_sync {
+ my ($self, $opts) = @_;
+ $opts ||= {};