v2writable: exact discontiguous history handling

We've always temporarily unindexeded messages before reindexing
them again if there's discontiguous history.

This change improves the mechanism we use to prevent NNTP and
IMAP clients from seeing duplicate messages.

Previously, we relied on mapping Message-IDs to NNTP article
numbers to ensure clients would not see the same message twice.
This worked for most messages, but not for for messages with
reused or duplicate Message-IDs.

Instead of relying on Message-IDs as a key, we now rely on the
git blob object ID for exact content matching.  This allows
truly different messages to show up for NNTP|IMAP clients, while
still those clients from seeing the message again.

0 files changed, 0 insertions, 0 deletions