--- /dev/null
+# Copyright (C) all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+
+# common git alternates + all.git||ALL.git management code
+package PublicInbox::MultiGit;
+use strict;
+use v5.10.1;
+use PublicInbox::Spawn qw(run_die);
+use PublicInbox::Import;
+use File::Temp 0.19;
+use List::Util qw(max);
+
+sub new {
+ my ($cls, $topdir, $all, $epfx) = @_;
+ bless {
+ topdir => $topdir, # inboxdir || extindex.*.topdir
+ all => $all, # all.git or ALL.git
+ epfx => $epfx, # "git" (inbox) or "local" (lei/store)
+ }, $cls;
+}
+
+sub read_alternates {
+ my ($self, $moderef, $prune) = @_;
+ my $objpfx = "$self->{topdir}/$self->{all}/objects/";
+ my $f = "${objpfx}info/alternates";
+ my %alt; # line => score
+ my %seen; # $st_dev\0$st_ino => count
+ my $other = 0;
+ if (open(my $fh, '<', $f)) {
+ my $is_edir = defined($self->{epfx}) ?
+ qr!\A\Q../../$self->{epfx}\E/([0-9]+)\.git/objects\z! :
+ undef;
+ $$moderef = (stat($fh))[2] & 07777;
+ for my $rel (split(/^/m, do { local $/; <$fh> })) {
+ chomp(my $dir = $rel);
+ my $score;
+ if (defined($is_edir) && $dir =~ $is_edir) {
+ $score = $1 + 0;
+ substr($dir, 0, 0) = $objpfx;
+ } else { # absolute paths, if any (extindex)
+ $score = --$other;
+ }
+ if (my @st = stat($dir)) {
+ next if $seen{"$st[0]\0$st[1]"}++;
+ $alt{$rel} = $score;
+ } else {
+ warn "W: stat($dir) failed: $! ($f)";
+ $alt{$rel} = $score unless $prune;
+ }
+ }
+ } elsif (!$!{ENOENT}) {
+ die "E: open($f): $!";
+ }
+ (\%alt, \%seen);
+}
+
+sub epoch_dir { "$_[0]->{topdir}/$_[0]->{epfx}" }
+
+sub write_alternates {
+ my ($self, $mode, $alt, @new) = @_;
+ my $all_dir = "$self->{topdir}/$self->{all}";
+ PublicInbox::Import::init_bare($all_dir);
+ my $out = join('', sort { $alt->{$b} <=> $alt->{$a} } keys %$alt);
+ my $info_dir = "$all_dir/objects/info";
+ my $fh = File::Temp->new(TEMPLATE => 'alt-XXXX', DIR => $info_dir);
+ my $f = $fh->filename;
+ print $fh $out, @new or die "print($f): $!";
+ chmod($mode, $fh) or die "fchmod($f): $!";
+ close $fh or die "close($f): $!";
+ my $fn = "$info_dir/alternates";
+ rename($f, $fn) or die "rename($f, $fn): $!";
+ $fh->unlink_on_destroy(0);
+}
+
+# returns true if new epochs exist
+sub merge_epochs {
+ my ($self, $alt, $seen) = @_;
+ my $epoch_dir = epoch_dir($self);
+ if (opendir my $dh, $epoch_dir) {
+ my $has_new;
+ for my $bn (grep(/\A[0-9]+\.git\z/, readdir($dh))) {
+ my $rel = "../../$self->{epfx}/$bn/objects\n";
+ next if exists($alt->{$rel});
+ if (my @st = stat("$epoch_dir/$bn/objects")) {
+ next if $seen->{"$st[0]\0$st[1]"}++;
+ $alt->{$rel} = substr($bn, 0, -4) + 0;
+ $has_new = 1;
+ } else {
+ warn "E: stat($epoch_dir/$bn/objects): $!";
+ }
+ }
+ $has_new;
+ } else {
+ $!{ENOENT} ? undef : die "opendir($epoch_dir): $!";
+ }
+}
+
+sub fill_alternates {
+ my ($self) = @_;
+ my ($alt, $seen) = read_alternates($self, \(my $mode = 0644));
+ merge_epochs($self, $alt, $seen) and
+ write_alternates($self, $mode, $alt);
+}
+
+sub epoch_cfg_set {
+ my ($self, $epoch_nr) = @_;
+ run_die([qw(git config -f), epoch_dir($self)."/$epoch_nr.git/config",
+ 'include.path', "../../$self->{all}/config" ]);
+}
+
+sub add_epoch {
+ my ($self, $epoch_nr) = @_;
+ my $git_dir = epoch_dir($self)."/$epoch_nr.git";
+ my $f = "$git_dir/config";
+ my $existing = -f $f;
+ PublicInbox::Import::init_bare($git_dir);
+ epoch_cfg_set($self, $epoch_nr) unless $existing;
+ fill_alternates($self);
+ $git_dir;
+}
+
+sub git_epochs {
+ my ($self) = @_;
+ if (opendir(my $dh, epoch_dir($self))) {
+ my @epochs = map {
+ substr($_, 0, -4) + 0; # drop ".git" suffix
+ } grep(/\A[0-9]+\.git\z/, readdir($dh));
+ wantarray ? sort { $b <=> $a } @epochs : (max(@epochs) // 0);
+ } elsif ($!{ENOENT}) {
+ wantarray ? () : 0;
+ } else {
+ die(epoch_dir($self).": $!");
+ }
+}
+
+1;