[PATCH 08/11] lib: Implement upgrade to ghost messages feature

[David Bremner]

Austin Clements <aclements at csail.mit.edu> writes:
> +    if (new_features & NOTMUCH_FEATURE_GHOSTS) {
> +	t_end = db->metadata_keys_end ("thread_id_");
> +	for (t = db->metadata_keys_begin ("thread_id_"); t != t_end; ++t)
> +	    ++total;
> +    }

It would be nice to have the comment below, or something like it, for
the loop above.

> +    /* Perform metadata upgrades. */
> +
> +    /* Prior to NOTMUCH_FEATURE_GHOSTS, thread IDs for missing
> +     * messages were stored as database metadata. Change these to
> +     * ghost messages.
> +     */