feed: comment about the %deleted hash

It's strictly not necessary anymore since
commit fa6168c56bdd1cece178b6b852a9b2cba6ce6ffb
("feed: message must exist in current HEAD to show up")

However it can still save us some unnecessary syscalls and
round-trips to the "git cat-file --batch" process, so it's probably
worth th cost of stuffing it in a hash.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/Feed.pm b/lib/PublicInbox/Feed.pm
index 3b2b7af9..a8578e76 100644
--- a/lib/PublicInbox/Feed.pm
+++ b/lib/PublicInbox/Feed.pm
@@ -156,7 +156,7 @@ sub each_recent_blob {
 
         my $pid = open(my $log, '-|', @cmd) or
                 die('open `'.join(' ', @cmd) . " pipe failed: $!\n");
-        my %deleted;
+        my %deleted; # only an optimization at this point
         my $last;
         my $nr = 0;
         my @commits = ();