Tag duplicate messages with notmuch insert

[Thomas Schneider]

>From notmuch-insert(1):

> If the new message is a duplicate of an existing message in the
> database (it has same Message-ID), it will be added to the maildir
> folder and notmuch database, but the tags will not be changed.

It might however be desired to apply the new tags even when the message
is a duplicate.  How complicated would it be to implement this?