mbox: do not clobber existing archive headers in WWW

When serving archives, it's more robust to keep existing
archive links in one server goes down.

diff --git a/lib/PublicInbox/Mbox.pm b/lib/PublicInbox/Mbox.pm
index 9f20580e31f0ec6a888911e7056fdde30d2ede1d..ffa6fa47841846b43a332f3454f7eee9abca50a5 100644 (file)
--- a/lib/PublicInbox/Mbox.pm
+++ b/lib/PublicInbox/Mbox.pm
@@ -48,11 +48,21 @@ sub emit_msg {
        my $base = $feed_opts->{url};
        my $mid = mid_clean($header_obj->header('Message-ID'));
        $mid = uri_escape_utf8($mid);
-       my @archived_at = $header_obj->header('Archived-At');
-       push @archived_at, "<$base$mid/>";
-       $header_obj->header_set('Archived-At', @archived_at);
-       $header_obj->header_set('List-Archive', "<$base>");
-       $header_obj->header_set('List-Post', "<mailto:$feed_opts->{id_addr}>");
+       my %append = (
+               'Archived-At' => "<$base$mid/>",
+               'List-Archive' => "<$base>",
+               'List-Post' => "<mailto:$feed_opts->{id_addr}>",
+       );
+       while (my ($k, $v) = each %append) {
+               my @v = $header_obj->header($k);
+               foreach (@v) {
+                       if ($v eq $_) {
+                               $v = undef;
+                               last;
+                       }
+               }
+               $header_obj->header_set($k, @v, $v) if defined $v;
+       }
 
        my $buf = $header_obj->as_string;
        unless ($buf =~ /\AFrom /) {