From 375b3ccfd3ca978281cb3869b62fc91eebc60d6e Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Wed, 15 Sep 2021 11:26:17 +0000
Subject: multi_git: hoist out common epoch/alternates handling

IMHO, this greatly improves code sharing and organization
between v2, extindex, and lei/store.  Common git-related
logic for these is lightly-refactored and easier to reason
about.

The impetus for this big change was to ensure inboxes
created+managed by public-inbox-{clone,fetch} could have
alternates and configs setup properly without depending on
SQLite (via V2Writable).  This change does that while
making old code shorter and better factored.
---
 lib/PublicInbox/MultiGit.pm | 136 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)
 create mode 100644 lib/PublicInbox/MultiGit.pm

(limited to 'lib/PublicInbox/MultiGit.pm')

diff --git a/lib/PublicInbox/MultiGit.pm b/lib/PublicInbox/MultiGit.pm
new file mode 100644
index 00000000..91d7998a
--- /dev/null
+++ b/lib/PublicInbox/MultiGit.pm
@@ -0,0 +1,136 @@
+# 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;
-- 
cgit v1.2.3-24-ge0c7