[PATCH] dump: make dump take Xapian write lock

[David Bremner]

Mark Walters <markwalters1009 at gmail.com> writes:

> Dump currently only takes the read lock. Xapian can cope with some
> changes while maintaining a read snapshot but with more changes it
> fails. Currently notmuch just gives a xapian error.
>
> To avoid this we take the write lock when dumping. This prevents other
> notmuch processes from modifying the xapian database preventing this
> error.

pushed. This needs a NEWS item.

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