www: support cloning individual v2 git partitions

This will require multiple client invocations, but should reduce
load on the server and make it easier for readers to only clone
the latest data.

Unfortunately, supporting a cloneurl file for externally-hosted
repos will be more difficult as we cannot easily know if the
clones use v1 or v2 repositories, or how many git partitions
they have.

3 files changed, 66 insertions, 13 deletions

diff --git a/lib/PublicInbox/Inbox.pm b/lib/PublicInbox/Inbox.pm
index b1ea8dc7..30977514 100644
--- a/lib/PublicInbox/Inbox.pm
+++ b/lib/PublicInbox/Inbox.pm
@@ -82,6 +82,18 @@ sub new {
         bless $opts, $class;
 }
 
+sub git_part {
+        my ($self, $part) = @_;
+        ($self->{version} || 1) == 2 or return;
+        $self->{"$part.git"} ||= eval {
+                my $git_dir = "$self->{mainrepo}/git/$part.git";
+                my $g = PublicInbox::Git->new($git_dir);
+                $g->{-httpbackend_limiter} = $self->{-httpbackend_limiter};
+                # no cleanup needed, we never cat-file off this, only clone
+                $g;
+        };
+}
+
 sub git {
         my ($self) = @_;
         $self->{git} ||= eval {
@@ -94,6 +106,29 @@ sub git {
         };
 }
 
+sub max_git_part {
+        my ($self) = @_;
+        my $v = $self->{version};
+        return unless defined($v) && $v == 2;
+        my $part = $self->{-max_git_part};
+        my $changed = git($self)->alternates_changed;
+        if (!defined($part) || $changed) {
+                $self->git->cleanup if $changed;
+                my $gits = "$self->{mainrepo}/git";
+                if (opendir my $dh, $gits) {
+                        my $max = -1;
+                        while (defined(my $git_dir = readdir($dh))) {
+                                $git_dir =~ m!\A(\d+)\.git\z! or next;
+                                $max = $1 if $1 > $max;
+                        }
+                        $part = $self->{-max_git_part} = $max if $max >= 0;
+                } else {
+                        warn "opendir $gits failed: $!\n";
+                }
+        }
+        $part;
+}
+
 sub mm {
         my ($self) = @_;
         $self->{mm} ||= eval {
@@ -133,7 +168,7 @@ sub description {
         local $/ = "\n";
         chomp $desc;
         $desc =~ s/\s+/ /smg;
-        $desc = '($GIT_DIR/description missing)' if $desc eq '';
+        $desc = '($REPO_DIR/description missing)' if $desc eq '';
         $self->{description} = $desc;
 }
 
diff --git a/lib/PublicInbox/WWW.pm b/lib/PublicInbox/WWW.pm
index a2c2a4a6..7bd29732 100644
--- a/lib/PublicInbox/WWW.pm
+++ b/lib/PublicInbox/WWW.pm
@@ -54,10 +54,10 @@ sub call {
         my $method = $env->{REQUEST_METHOD};
 
         if ($method eq 'POST') {
-                if ($path_info =~ m!$INBOX_RE/(git-upload-pack)\z!) {
-                        my $path = $2;
+                if ($path_info =~ m!$INBOX_RE/(?:(\d+)/)?(git-upload-pack)\z!) {
+                        my ($part, $path) = ($2, $3);
                         return invalid_inbox($ctx, $1) ||
-                                serve_git($ctx, $path);
+                                serve_git($ctx, $part, $path);
                 } elsif ($path_info =~ m!$INBOX_RE/!o) {
                         return invalid_inbox($ctx, $1) || mbox_results($ctx);
                 }
@@ -77,10 +77,10 @@ sub call {
                 invalid_inbox($ctx, $1) || get_atom($ctx);
         } elsif ($path_info =~ m!$INBOX_RE/new\.html\z!o) {
                 invalid_inbox($ctx, $1) || get_new($ctx);
-        } elsif ($path_info =~ m!$INBOX_RE/
+        } elsif ($path_info =~ m!$INBOX_RE/(?:(\d+)/)?
                                 ($PublicInbox::GitHTTPBackend::ANY)\z!ox) {
-                my $path = $2;
-                invalid_inbox($ctx, $1) || serve_git($ctx, $path);
+                my ($part, $path) = ($2, $3);
+                invalid_inbox($ctx, $1) || serve_git($ctx, $part, $path);
         } elsif ($path_info =~ m!$INBOX_RE/([\w-]+).mbox\.gz\z!o) {
                 serve_mbox_range($ctx, $1, $2);
         } elsif ($path_info =~ m!$INBOX_RE/$MID_RE/$END_RE\z!o) {
@@ -393,8 +393,11 @@ sub msg_page {
 }
 
 sub serve_git {
-        my ($ctx, $path) = @_;
-        PublicInbox::GitHTTPBackend::serve($ctx->{env}, $ctx->{git}, $path);
+        my ($ctx, $part, $path) = @_;
+        my $env = $ctx->{env};
+        my $ibx = $ctx->{-inbox};
+        my $git = defined $part ? $ibx->git_part($part) : $ibx->git;
+        $git ? PublicInbox::GitHTTPBackend::serve($env, $git, $path) : r404();
 }
 
 sub mbox_results {
diff --git a/lib/PublicInbox/WwwStream.pm b/lib/PublicInbox/WwwStream.pm
index 05519984..76317544 100644
--- a/lib/PublicInbox/WwwStream.pm
+++ b/lib/PublicInbox/WwwStream.pm
@@ -72,17 +72,32 @@ sub _html_end {
         my $obj = $ctx->{-inbox};
         my $desc = ascii_html($obj->description);
 
+        my (%seen, @urls);
         my $http = $obj->base_url($ctx->{env});
-        chop $http;
-        my %seen = ( $http => 1 );
-        my @urls = ($http);
+        chop $http; # no trailing slash
+        my $part = $obj->max_git_part;
+        if (defined($part)) { # v2
+                # most recent partition first:
+                for (; $part >= 0; $part--) {
+                        my $url = "$http/$part";
+                        $seen{$url} = 1;
+                        push @urls, $url;
+                }
+        } else { # v1
+                $seen{$http} = 1;
+                push @urls, $http;
+        }
+
+        # FIXME: partitioning in can be different in other repositories,
+        # use the "cloneurl" file as-is for now:
         foreach my $u (@{$obj->cloneurl}) {
                 next if $seen{$u};
                 $seen{$u} = 1;
                 push @urls, $u =~ /\Ahttps?:/ ? qq(<a\nhref="$u">$u</a>) : $u;
         }
+
         if (scalar(@urls) == 1) {
-                $urls .= " git clone --mirror $http";
+                $urls .= " git clone --mirror $urls[0]";
         } else {
                 $urls .= "\n" .
                         join("\n", map { "\tgit clone --mirror $_" } @urls);