init: reduce git-config execve for idempotent cases

This probably saves us a few cycles in some cases since spawning
new processes is expensive.

diff --git a/script/public-inbox-init b/script/public-inbox-init
index b3f60bad7e3fd9d13440999cc5157fe0f6c2f57d..b9e234e30872c6aded7c093192796b94cfc71bd3 100755 (executable)
--- a/script/public-inbox-init
+++ b/script/public-inbox-init
@@ -125,7 +125,7 @@ sysopen($lockfh, $lockfile, O_RDWR|O_CREAT|O_EXCL) or do {
 require PublicInbox::OnDestroy;
 my $auto_unlink = PublicInbox::OnDestroy::on_destroy(sub { unlink $lockfile });
 my $perm = 0644 & ~umask;
-my %seen;
+my (%seen, $old_ibx);
 if (-e $pi_config) {
        require PublicInbox::IO;
        open(my $oh, '<', $pi_config);
@@ -156,8 +156,8 @@ if (-e $pi_config) {
 
        exit(1) if $conflict;
 
-       my $ibx = $cfg->lookup_name($name);
-       $indexlevel //= $ibx->{indexlevel} if $ibx;
+       $old_ibx = $cfg->lookup_name($name);
+       $indexlevel //= $old_ibx->{indexlevel} if $old_ibx;
 }
 my $pi_config_tmp = $fh->filename;
 close($fh);
@@ -224,17 +224,17 @@ umask(0077);
 require PublicInbox::Spawn;
 PublicInbox::Spawn->import(qw(run_die));
 
-foreach my $addr (@address) {
-       next if $seen{lc($addr)};
+for my $addr (grep { !$seen{lc $_} } @address) {
        run_die([@x, "--add", "$pfx.address", $addr]);
 }
-run_die([@x, "$pfx.url", $http_url]);
-run_die([@x, "$pfx.inboxdir", $inboxdir]);
-
-if (defined($indexlevel)) {
-       run_die([@x, "$pfx.indexlevel", $indexlevel]);
-}
-run_die([@x, "$pfx.newsgroup", $ng]) if $ng ne '';
+run_die([@x, "$pfx.url", $http_url]) if
+       (!$old_ibx || !grep(/\Q$http_url\E/, @{$old_ibx->{url} // []}));
+run_die([@x, "$pfx.inboxdir", $inboxdir]) if
+       (!$old_ibx || ($old_ibx->{inboxdir} ne $inboxdir));
+run_die([@x, "$pfx.indexlevel", $indexlevel]) if defined($indexlevel) &&
+       (!$old_ibx || (($old_ibx->{indexlevel} // '') ne $indexlevel));
+run_die([@x, "$pfx.newsgroup", $ng]) if $ng ne '' &&
+       (!$old_ibx || (($old_ibx->{newsgroup} // '') ne $ng));
 
 for my $kv (@c_extra) {
        my ($k, $v) = split(/=/, $kv, 2);