searchidx: ensure duplicated Message-IDs can be linked together

This allows us to emulate the display of thread-aware MUAs when
multiple messages share the same Message-ID.  This also is a
place where "public-inbox-index --reindex" is useful to fix
existing messages and no schema version bump is necessary.

1 files changed, 3 insertions, 0 deletions

diff --git a/t/psgi_v2.t b/t/psgi_v2.t
index aa3279cc..bdf23deb 100644
--- a/t/psgi_v2.t
+++ b/t/psgi_v2.t
@@ -182,6 +182,9 @@ test_psgi(sub { $www->call(@_) }, sub {
         $res = $cb->(GET('/v2test/reuse@mid/T/'));
         $raw = $res->content;
         like($raw, qr/\b4\+ messages\b/, 'thread overview shown with /T/');
+        my @over = ($raw =~ m/^\d{4}-\d+-\d+\s+\d+:\d+ (.+)$/gm);
+        is_deeply(\@over, [ '<a', '` <a', '` <a', '` <a' ],
+                'duplicate messages share the same root');
 
         $res = $cb->(GET('/v2test/reuse@mid/t/'));
         $raw = $res->content;